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This study examines the intermolecular interactions between small molecules and solvents, with a particular focus on pyruvic acid (PA). PA plays a significant role in biochemistry, astrochemistry, and atmospheric chemistry, particularly in aerosol particle formation. Previous studies on PA have been expanded upon by exploring its hydration and complexation with 2,2,2-trifluoroethanol (TFE). The clusters were generated using a supersonic expansion and characterized by broadband Fourier transform microwave spectroscopy. The structures of the clusters were identified by comparing the experimental results with high-level quantum-chemical computations. Among the possible isomers for the hydrated complex, the Tc-(H2O)2 kinetic complex, where PA exhibits an internal hydrogen bond, was favored over the Tt-(H2O)2 form, predicted to be the most stable conformer. Transitions from both the A and E internal rotation substates were observed exclusively in the dihydrate. The complex with TFE did not exhibit splitting due to the internal rotation of the methyl top. This is attributed to the presence of electronegative fluorine groups in TFE, stabilizing the complex through additional CH⋯F interactions, thereby hindering the internal rotation motion of the methyl top. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in space and govern the interstellar chemistry. The two isomers of cyanonaphthalene (1-CNN and 2-CNN) were the first PAHs to be recently identified in the Taurus Molecular Cloud (TMC-1). Their large abundance is attributed to high photostability with nearly no photofragmentation at photon energies above the ionization potential. Here, we show that at ambient light and at densities akin to dense molecular clouds and the upper atmosphere of planets and moons, 1-CNN could undergo extensive fragmentation through a new mechanism leading to daughter cations. On UV photoexcitation, at a photon energy way below the ionization threshold, 1-CNN monomers form photoexcited dimer units. Intermolecular Coulombic decay between the two photoexcited units of the dimer leads to ionization, and the subsequent molecular rearrangements form new daughter cations. These daughter cations could react further, contributing to rich bottom-up astrochemistry, and could play a pivotal role in developmental astrobiology. Photofragmentation in atmospheric and astrophysical environments is hitherto known to be unimolecular, while the present results point a pathway involving bimolecular photofragmentation. [ABSTRACT FROM AUTHOR]

FU Ori– and EX Lup–type objects present natural experiments for understanding a critical stage in the star and planet formation process. These objects offer insight into the diversity of molecules available to forming planetary systems due to a sudden increase in accretion, and central luminosity causes the disk and surrounding material to increase in temperature. This allows for volatiles to sublimate off of grains and exist in the gas phase for tens to hundreds of years after initial outburst. While this dynamic stage may be common for solar-type protostars, observations of the chemical impact of these bursts are rare. In this article, we present observations from the NOrthern Extended Millimeter Array of five young stellar objects (YSOs) that have undergone outbursts within the past 100 yr and catalog the volatile chemistry found within ∼1000 au of the YSO. Only one source clearly shows a line-rich spectra with >11 molecules detected, including complex organics and water, as is expected for a spectra signature for a postoutburst source. This source is V1057 Cyg, and we present it as the northern analog to the well-studied and molecule-rich FU Ori source, V883 Ori. Our conclusions on the chemical inventory of the other four sources in our sample are sensitivity limited, as V1057 Cyg contains the highest disk/envelope gas mass. [ABSTRACT FROM AUTHOR]

We report the first detection of the metal-bearing molecules sodium sulfide and magnesium sulfide and the tentative detection of calcium monoxide in the interstellar medium toward the Galactic center molecular cloud G+0.693-0.027. The derived column densities are (5.0 ± 1.1) × 1010 cm−2, (6.0 ± 0.6) × 1010 cm−2, and (2.0 ± 0.5) × 1010 cm−2, respectively. This translates into fractional abundances with respect to H2 of (3.7 ± 1.0) × 10−13, (4.4 ± 0.8) × 10−13, and (1.5 ± 0.4) × 10−13, respectively. We have also searched for other Na-, Mg-, and Ca-bearing species toward this source but none of them have been detected and thus we provide upper limits for their abundances. We discuss the possible chemical routes involved in the formation of these molecules containing metals under interstellar conditions. Finally, we compare the ratio between sulfur-bearing and oxygen-bearing molecules with and without metals, finding that metal-bearing sulfur molecules are much more abundant than metal-bearing oxygen ones, in contrast with the general trend found in the ratios between other nonmetal-oxygen- and sulfur-bearing molecules. This further strengthens the idea that sulfur may be a little depleted in G+0.693-0.027 as a result of the low-velocity shocks present in this source sputtering large amounts of material from dust grains. [ABSTRACT FROM AUTHOR]

Planet formation is strongly influenced by the composition and distribution of volatiles within protoplanetary disks. With JWST, it is now possible to obtain direct observational constraints on disk ices, as recently demonstrated by the detection of ice absorption features toward the edge-on HH 48 NE disk as part of the Ice Age Early Release Science program. Here, we introduce a new radiative transfer modeling framework designed to retrieve the composition and mixing status of disk ices using their band profiles, and apply it to interpret the H2O, CO2, and CO ice bands observed toward the HH 48 NE disk. We show that the ices are largely present as mixtures, with strong evidence for CO trapping in both H2O and CO2 ice. The HH 48 NE disk ice composition (pure versus polar versus apolar fractions) is markedly different from earlier protostellar stages, implying thermal and/or chemical reprocessing during the formation or evolution of the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk, and also demonstrate that the mixing and entrapment of disk ices can dramatically affect the radial dependence of the C/O ratio. It is therefore imperative that realistic disk ice compositions are considered when comparing planetary compositions with potential formation scenarios, which will fortunately be possible for an increasing number of disks with JWST. [ABSTRACT FROM AUTHOR]

A recent publication described laboratory measurements of infrared spectra of solid 1-propanol, a likely interstellar ice component. The authors concluded that amorphous 1-propanol does not produce crystalline 1-propanol on warming and that 1-propanol remains as a solid far above its melting point. New laboratory results presented here show that both conclusions are false. A spectrum of crystalline 1-propanol is presented along with the first band strengths for two infrared features in both the amorphous and crystalline forms of the compound. Extensions and astrochemical applications are described. [ABSTRACT FROM AUTHOR]

The anions C |$_7$| N |$^-$| and C |$_{10}$| H |$^-$| are the two longest of the linear (C,N)-bearing and (C,H)-bearing chains that have so far been detected in the interstellar medium (ISM). In order to glean information on their collision-induced rotational state-changing processes, we analyse the general features of new ab initio potentials describing the interaction of both linear anions with H |$_2$|⁠ , one of the most abundant partners in their ISM environment. We employ an artificial neural network fit of the reduced-dimensionality potential energy surface for C |$_7$| N |$^-$|⁠...H |$_2$| interaction and discuss in detail the spatial features in terms of multipolar radial coefficients. For the C |$_{10}$| H |$^-$|⁠...H |$_2$| interaction, we use the initial grid of two-dimensional raw points to generate by quadrature the Legendre expansion directly, further including the long-range terms as discussed in the main text. Quantum scattering calculations are employed to obtain rotationally inelastic cross-sections, for collision energies in the range of 10 |$^{-4}$| to 400 cm |$^{-1}$|⁠. From them we generate the corresponding inelastic rate coefficients as a function of temperature covering the range from 10 to 50 K. The results for the rate coefficients for the longest cyanopolyyne are compared with the earlier results obtained for the smaller terms of the same series, also in collision with H |$_2$|⁠. We obtain that the inelastic rate coefficients for the long linear anions are all fairly large compared with the earlier systems. The consequences of such findings on their non-equilibrium rotational populations in interstellar environments are illustrated in our conclusions. [ABSTRACT FROM AUTHOR]

The existence of organic matter presenting a high molecular diversity in extraterrestrial environments is well documented. To understand the origin of this organic diversity, laboratory experiments were developed and showed that irradiation and thermal alteration of simple molecules such as methanol, water, and ammonia in conditions mimicking astrophysical ice environments. Ices containing water, methanol, and ammonia (H2O: MeOH: NH3) photolyzed and monitored by infrared spectroscopy, while the organic matter formed at room temperature was analyzed in situ with infrared spectroscopy and ex situ with high-resolution mass spectrometry. Those ices irradiated at 77 K and 10−8 mbar shows a significant organic molecular diversity: residual organic compounds contain up to 78 C, 188 H, 123 N, and 37 O. Most of them contains all four CHNO atoms (76–86 per cent), followed by CHO (11–17 per cent), and CHN compounds (5–6 per cent). CHNO and CHO compounds are more aliphatic (34–53 per cent), while CHN compounds are mostly condensed aromatics (83–90 per cent). In this work, our objective is to investigate impacts of environment on this organic molecular diversity by focusing on three parameters: photon dose, pressure, and heating rate during the warming process. Analyses of the residue formed showed that the heating rate and pressure weakly alter the abundance of the final organic material, while the irradiation rate reduced its abundance at high photon doses by a factor of 8. These results give insights on the impact of icy environment conditions in the evolution of astrophysical organic matter. [ABSTRACT FROM AUTHOR]

The anions C |$_7$| N |$^-$| and C |$_{10}$| H |$^-$| are the two longest of the linear (C,N)-bearing and (C,H)-bearing chains that have so far been detected in the interstellar medium (ISM). In order to glean information on their collision-induced rotational state-changing processes, we analyse the general features of new ab initio potentials describing the interaction of both linear anions with H |$_2$|⁠ , one of the most abundant partners in their ISM environment. We employ an artificial neural network fit of the reduced-dimensionality potential energy surface for C |$_7$| N |$^-$|⁠...H |$_2$| interaction and discuss in detail the spatial features in terms of multipolar radial coefficients. For the C |$_{10}$| H |$^-$|⁠...H |$_2$| interaction, we use the initial grid of two-dimensional raw points to generate by quadrature the Legendre expansion directly, further including the long-range terms as discussed in the main text. Quantum scattering calculations are employed to obtain rotationally inelastic cross-sections, for collision energies in the range of 10 |$^{-4}$| to 400 cm |$^{-1}$|⁠. From them we generate the corresponding inelastic rate coefficients as a function of temperature covering the range from 10 to 50 K. The results for the rate coefficients for the longest cyanopolyyne are compared with the earlier results obtained for the smaller terms of the same series, also in collision with H |$_2$|⁠. We obtain that the inelastic rate coefficients for the long linear anions are all fairly large compared with the earlier systems. The consequences of such findings on their non-equilibrium rotational populations in interstellar environments are illustrated in our conclusions. [ABSTRACT FROM AUTHOR]

Heterocycles have not been detected in the interstellar medium (ISM) yet. However, the direct involvement of some pentagonal heterocycles within the formation of key biomolecules for the origin of life makes the search for these systems in the ISM relevant for understanding whether some of the bricks of life could be formed in the ISM. We have explored the possible formation of the simple heterocycle furan (c-C |$_{4}$| H |$_{4}$| O) under interstellar conditions, through the reaction between two interstellar species, |$\mathrm{syn}$| -vinyl alcohol (⁠|$\mathrm{syn}$| -VA) and the CCH radical. We employed state-of-the-art quantum-chemical calculations to elucidate the reaction mechanism between the reaction of CCH radical and |$\mathrm{syn}$| -VA. Kinetic simulations were carried out aiming to quantitatively assess the viability of this reaction in the ISM. We have found a reaction pathway to furan where all energy barriers are submerged. However, the formation of this heterocycle is not feasible because the intermediates leading to furan can evolve through more favourable routes. In contrast, we have found viable pathways for the formation of the four isomers of 1-butenol-3-yne (HCCCHCHOH) (Z - |$\mathrm{syn}$|⁠ , E - |$\mathrm{syn}$|⁠ , E - |$\mathrm{anti}$|⁠ , and Z - |$\mathrm{anti}$|⁠), which thus are promising species to be detected in the ISM. Our theoretical work indicates that the four isomers of 1-butenol-3-yne should be present in the ISM because the precursors are known interstellar species, and the kinetic simulations indicate that their formation is very likely. We then encourage the observational search of these molecules in the ISM. [ABSTRACT FROM AUTHOR]

In the planetary atmosphere, hydrogen cyanide (HCN) is an important nitrogen (N)-bearing molecule that plays a key role in the formation of several biomolecules via chain reactions. The presence of HCN characterizes the stratospheric composition of the solar gas planets and exoplanets. For several years, many observations have failed to identify the rotational and vibrational emission lines of HCN from the atmosphere of Saturn using ground- and space-based radio telescopes. We present the successful detection of the rotational emission line of HCN from the atmosphere of Saturn using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 7. We detected the J = 4 –3 transition line of the HCN from the eastern and western limbs of Saturn with ≥ 5 σ statistical significance. The derived abundances of HCN in the western and eastern limbs are 6.19 and 2.90 ppb, respectively. We claim that HCN is formed in the atmosphere of Saturn via the photolysis of methane ( CH 4 ) and ammonia ( NH 3 ). [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/submillimeter Array observations of SiO, SiS, H2O, NaCl, and SO line emission at ∼30–50 mas resolution. These images map the molecular outflow and disk of Orion Source I (SrcI) on ∼12–20 au scales. Our observations show that the flow of material around SrcI creates a turbulent boundary layer in the outflow from SrcI, which may dissipate angular momentum in the rotating molecular outflow into the surrounding medium. Additionally, the data suggest that the proper motion of SrcI may have a significant effect on the structure and evolution of SrcI and its molecular outflow. As the motion of SrcI funnels material between the disk and the outflow, some material may be entrained into the outflow and accrete onto the disk, creating shocks that excite the NaCl close to the disk surface. [ABSTRACT FROM AUTHOR]

SO and SO2 are two potential candidates to trace the different evolutionary phases of the low-mass star-formation process. Here, we report observations of SO and SO2 along with their isotopologues, 34SO and 34SO2, respectively, in four distinct phases of the low-mass star-formation process (prestellar core, first hydrostatic core, Class 0, and Class I) with an unbiased survey carried out using the Institut de Radioastronomie Millimetrique (IRAM) 30 m telescope. Interestingly, the estimated abundances of SO and SO2 show an increasing trend from the prestellar phase to the Class 0 stage and then a decrease in the Class I phase. A similar trend is obtained for OCS and H2S. In contrast, the obtained SO/SO2 ratio decreases gradually from the prestellar core to the Class I stage. We have used the three-phase Rokko chemical code to explain our observations. The modeled abundances of SO and SO2 exhibit an increase within the inner region as the cold gas transforms into a hot gas. The modeled abundance ratio of SO to SO2 exhibits a notably high value in cold gas environments. This ratio decreases to less than 1 within the temperature range of 100-300 K and then increases to approximately 1 beyond 300 K. In the outer region, the simulated ratio consistently exceeds the value of 1. Our work is an observational testbed for modeling the chemistry of SO/SO2 during low-mass star formation. However, our findings may require more sample sources with higher resolution and a more robust model for validation. [ABSTRACT FROM AUTHOR]

This study explores the electrochemical properties of the carbonaceous Allende CV3 meteorite, focusing on its potential as a Fe‐based catalyst derived from Mackinawite iron sulfide for electrocatalytic reactions facilitating nitrogen (N2) fixation into ammonia. Through comprehensive analysis, we not only monitored the evolution of key compounds such as CN‐, sulfur/H2S, H2 and carbonyl compounds, but also identified potential reagent carriers, indicating significant implications for the Strecker synthesis of amino acids in space environments. Initial examination revealed the presence of polypeptides, notably sequences including dimer Ala‐α‐HO‐Gly, pentamer Gly3‐Ala2, and hexamer Gly4‐(HO‐Gly)2. These discoveries greatly enhance our understanding of astrobiological chemistry, offering valuable insights into prebiotic processes and the potential presence of life‐building blocks throughout the universe. [ABSTRACT FROM AUTHOR]

SO and SO2 are two potential candidates to trace the different evolutionary phases of the low-mass star-formation process. Here, we report observations of SO and SO2 along with their isotopologues, 34SO and 34SO2, respectively, in four distinct phases of the low-mass star-formation process (prestellar core, first hydrostatic core, Class 0, and Class I) with an unbiased survey carried out using the Institut de Radioastronomie Millimetrique (IRAM) 30 m telescope. Interestingly, the estimated abundances of SO and SO2 show an increasing trend from the prestellar phase to the Class 0 stage and then a decrease in the Class I phase. A similar trend is obtained for OCS and H2S. In contrast, the obtained SO/SO2 ratio decreases gradually from the prestellar core to the Class I stage. We have used the three-phase Rokko chemical code to explain our observations. The modeled abundances of SO and SO2 exhibit an increase within the inner region as the cold gas transforms into a hot gas. The modeled abundance ratio of SO to SO2 exhibits a notably high value in cold gas environments. This ratio decreases to less than 1 within the temperature range of 100-300 K and then increases to approximately 1 beyond 300 K. In the outer region, the simulated ratio consistently exceeds the value of 1. Our work is an observational testbed for modeling the chemistry of SO/SO2 during low-mass star formation. However, our findings may require more sample sources with higher resolution and a more robust model for validation. [ABSTRACT FROM AUTHOR]

Observations of low-mass protostellar systems show evidence of rich, complex organic chemistry. Their low luminosity, however, makes determining abundance distributions of complex organic molecules within the water snowline challenging. However, the excitation conditions sampled by differing molecular distributions may produce substantive changes in the resulting emission. Thus, molecular excitation may recover spatial information from spatially unresolved data. By analyzing spatially unresolved NOrthern Extended Millimeter Array observations of CH3OH and CH3CN, we aim to determine if CH3OH and CH3CN are distributed differently in the protostellar disk around HOPS-370, a highly luminous intermediate-mass protostar. Rotational diagram analysis of CH3OH and CH3CN yields rotational temperatures of 198 ± 1.2 K and 448 ± 19 K, respectively, suggesting the two molecules have different spatial distributions. Source-specific 3D LTE radiative transfer models are used to constrain the spatial distribution of CH3OH and CH3CN within the disk. A uniform distribution with an abundance of 4 × 10−8 reproduces the CH3OH observations. In contrast, the spatial distribution of CH3CN needs to be either more compact (within ∼120 au versus ∼240 au for CH3OH) or exhibit a factor of ≳15 increase in abundance in the inner ∼55 au. A possible explanation for the difference in spatial abundance distributions of CH3OH and CH3CN is carbon-grain sublimation. [ABSTRACT FROM AUTHOR]

Methane (CH4) is one of the major components of the icy mantle of cosmic dust prevalent in cold, dense regions of interstellar media, playing an important role in the synthesis of complex organic molecules and prebiotic molecules. Solid CH4 is considered to be formed via the successive hydrogenation of C atoms accreting onto dust: C + 4H → CH4. However, most astrochemical models assume this reaction on the ice mantles of dust to be barrierless and efficient, without considering the states of adsorption. Recently, we found that C atoms exist in either the physisorbed or chemisorbed state on compact amorphous solid water, which is analogous to an interstellar ice mantle. These distinct adsorption states considerably affect the hydrogenation reactivity of the C atom. Herein, we elucidate the reactivities of physisorbed and chemisorbed C atoms with H atoms via sequential deposition and codeposition processes. The results indicate that only physisorbed C atoms can produce CH4 on ice. Combining this finding with a previous estimate for the fraction of physisorbed C atoms on ice, we determined the upper limit for the conversion of C atoms into CH4 to be 30%. [ABSTRACT FROM AUTHOR]

The recent detection of CN-functionalized aromatics partly addresses the long-standing mystery of the apparent absence of five- and six-membered rings in interstellar environments. Nitrogen (N)-heterocycles, which are crucial as the fundamental structures of nucleobases, have been a focus of these aromatic searches due to their biological significance. Although N-heterocycles have not been conclusively detected in astrophysical environments, their presence in chondrites and meteorites signifies their interstellar and circumstellar connection. Precise spectral data identify the unique signatures of molecules, confirming their presence in space. In this light, this work reports an extensive computational investigation on interstellar 3-pyrroline, a five-membered ring N-heterocycle. This includes an alternative formation route in cold interstellar environments and highly accurate rotational and vibrational spectroscopy. The results indicate that 3-pyrroline can form on dust grain surfaces from vinyl cyanide, as its formation from pyrrole through double hydrogenation may lead to the formation of pyrrole itself via an H2-abstraction process. 3-Pyrroline's rotational transition at 52.3 GHz offers a potential tool for its detection in cold interstellar regions. Additionally, the strongest infrared (IR) features of 3-pyrroline at 16.09 and |$\sim$| 3.50 |$\mu$| m are observable with JWST. The provided data are crucial for laboratory identification and future interstellar observations of 3-pyrroline at both radio and IR wavelengths. [ABSTRACT FROM AUTHOR]

Cold (⁠|$\sim$| 10 K) and dense (⁠|$\sim 10^{5}$| cm |$^{-3}$|⁠) cores of gas and dust within molecular clouds, known as starless and dynamically evolved pre-stellar cores, are the birthplaces of low-mass (M |$\le$| few M |$_\odot$|⁠) stars. As detections of interstellar complex organic molecules, or COMs, in starless cores has increased, abundance comparisons suggest that some COMs might be seeded early in the star formation process and inherited to later stages (i.e. protostellar discs and eventually comets). To date observations of COMs in starless cores have been limited, with most detections reported solely in the Taurus molecular cloud. It is therefore still a question whether different environments affect abundances. We have surveyed 35 starless and pre-stellar cores in the Perseus molecular cloud with the Arizona Radio Observatory (ARO) 12 m telescope detecting both methanol, CH |$_3$| OH, and acetaldehyde, CH |$_3$| CHO, in 100 per cent and 49 per cent of the sample, respectively. In the sub-sample of 15 cores where CH |$_3$| CHO was detected at |$\gt 3\sigma$| (⁠|$\sim$| 18 mK) with the ARO 12 m, follow-up observations with the Yebes 40 m telescope were carried out. Detections of formic acid, t -HCOOH, ketene, H |$_2$| CCO, methyl cyanide, CH |$_3$| CN, vinyl cyanide, CH |$_2$| CHCN, methyl formate, HCOOCH |$_3$|⁠ , and dimethyl ether, CH |$_3$| OCH |$_3$|⁠ , are seen in at least 20 per cent of the cores. We discuss detection statistics, calculate column densities, and compare abundances across various stages of low-mass star formation. Our findings have more than doubled COM detection statistics in cold cores and show COMs are prevalent in the gas before star and planet formation in the Perseus molecular cloud. [ABSTRACT FROM AUTHOR]

Aminoacetonitrile (AAN), also known as glycinenitrile, has been suggested as a possible precursor of glycine and adenine in the interstellar medium. Here, we present the chemical modelling of AAN and its isomers in hot cores using the three-phase chemical model NAUTILUS with the addition of over 300 chemical reactions of the three AAN isomers and related species. Our models predicted a peak gas-phase abundance of AAN reaching the order of 10 |$^{-8}$|⁠ , which is consistent with observation towards Sgr B2(N). Regarding the reaction pathways of AAN and its isomers, we found that AAN is primarily formed via free radical reactions on grain surfaces during the early evolutionary stages. Subsequently, it is thermally desorbed into the gas phase as the temperature rises and is then destroyed by positive ions and radicals in gas phase. The isomers of AAN are formed through the hydrogenation reaction of CH |$_3$| NCN on the grain surface and via electron recombination reactions of ion C |$_2$| H |$_5$| N |$_2^+$| in gas phase. We speculate that there is a possibility for NCCN and AAN to react with each other, eventually leading to the formation of adenine in hot cores. However, further investigation is required to understand the efficiency of grain surfaces in adenine formation, through theoretical calculations or laboratory experiments in future research. [ABSTRACT FROM AUTHOR]

We report the discovery in TMC-1 of two cyano derivatives of the PAH acenaphthylene (C12H8). We have found two series of lines with the QUIJOTE line survey that we assign to 1-C12H7CN and 5-C12H7CN. For the 1-isomer, we have detected and assigned 173 rotational transitions with J up to 46 and Ka up to 9, corresponding to 107 independent frequencies. For the 5-isomer, the identification is based on 56 individual lines, corresponding to 117 rotational transitions with J up to 40 and Ka up to 8. Identification of the carriers was achieved through a careful analysis of the derived rotational constants, which permit us to focus on molecules larger than naphthalene but smaller than anthracene and phenanthrene. Moreover, the derived rotational constants indicate that the species are planar; this allows us to discard derivatives of fluorene and acenaphthene, which are non-planar species. Quantum chemical calculations and subsequent chemical synthesis of these molecules, as well as the observation of their rotational transitions in the laboratory, unequivocally support our identifications. We also confirm, via a robust line-by-line detection, the previous claimed detection of 1- and 2-cyanonaphthalene, which were obtained through statistical stacking techniques. The column densities of 1- and 5-cyanoacenaphthylene are (9.5 ± 0.9) × 1011 cm−2, while those of 1- and 2-cyanonapthalene are (5.5 ± 0.5) × 1011 cm−2. Hence, it seems that acenaphthylene could be a factor of 1.7 more abundant than naphthalene. These results support a scenario in which PAHs grow in cold dark clouds based on fused five- and six-membered carbon rings. [ABSTRACT FROM AUTHOR]

In the absence of laboratory data, state-of-the-art quantum chemical approaches can provide estimates of the binding energy (BE) of interstellar species with grains. Without BE values, contemporary astrochemical models are compelled to utilize wild guesses, often delivering misleading information. Here, we employed a fully quantum chemical approach to estimate the BE of seven diatomic radicals – CH, NH, OH, SH, CN, NS, and NO – that play a crucial role in shaping the interstellar chemical composition, using a suitable amorphous solid water model as a substrate since water is the principal constituent of interstellar ice in dense and shielded regions. While the BEs are compatible with physisorption, the binding of CH in some sites shows chemisorption, in which a chemical bond to an oxygen atom of a water molecule is formed. While no structural change has been observed for the CN radical, it is believed that the formation of a hemibonded system between the outer layer of the water cluster and the radical is the reason for the unusually large BE in one of the binding sites considered in our study. A significantly lower BE for NO, consistent with recent calculations, is obtained, which helps explain the recently observed HONO/NH2OH and HONO/HNO ratios in the low-mass hot corino IRAS 16293–2422 B with chemical models. [ABSTRACT FROM AUTHOR]

Context. Carbonyl sulfide (OCS) is widely observed in the gas phase toward star-forming regions and was the first of the only two sulfur-bearing species to be detected in interstellar ices so far. However, the chemical network governing its formation is still not fully understood. While the sulfurization of CO and the oxidation of CS are often invoked to form OCS, other mechanisms could have a significant contribution. In particular, the multistep reaction involving CO and SH is a good candidate for forming a significant portion of the OCS in dense cloud environments. Aims. We aim to constrain the viability of the CO + SH route for forming solid OCS in the interstellar medium, in a similar manner as CO + OH is known to produce CO2 ice. This is achieved by conducting a systematic laboratory investigation of the targeted reactions on interstellar ice analogs under dense cloud conditions. Methods. We used an ultrahigh vacuum chamber to simultaneously deposit CO, H2S, and atomic H at 10 K. SH radicals produced in situ via hydrogen abstraction from H2S reacted with CO to form OCS. We monitored the ice composition during deposition and subsequent warm-up by means of Fourier-transform reflection absorption infrared spectroscopy (RAIRS). Complementarily, desorbed species were recorded with a quadrupole mass spectrometer (QMS) during temperature-programmed desorption (TPD) experiments. Control experiments were performed to secure the product identification. We also explored the effect of different H2S:CO mixing ratios – with decreasing H2S concentrations – on the OCS formation yield. Results. OCS is efficiently formed through surface reactions involving CO, H2S, and H atoms. The suggested underlying mechanism behind OCS formation is CO + SH → HSCO, followed by HSCO + H → OCS + H2. The OCS yield reduces slowly, but remains significant with increasing CO:H2S mixing ratios (CO:H2S = 1:1, 5:1, 10:1, and 20:1). Conclusions. Our experiments provide unambiguous evidence that OCS can be formed from CO + SH in the presence of H atoms. This route remains efficient for large H2S dilutions (5% with respect to CO), suggesting that it is a viable mechanism in interstellar ices. Given that SH radicals can be created in clouds over a wide evolutionary timescale, this mechanism could make a non-negligible contribution to the formation of interstellar OCS ice. [ABSTRACT FROM AUTHOR]

Context. Star formation in the central molecular zone (CMZ) is suppressed with respect to that of the Galactic disk, and this is likely related to its high turbulent environment. This turbulence impedes the potential detection of prestellar cores. Aims. We present the temperature, density, and spatial structure of the CMZ molecular cloud G+0.693-0.027, which has been proposed to host a prestellar cluster in the Sgr B2 region. Methods. We analysed multiple HC3N rotational transitions that were observed with the IRAM 30m, APEX, Yebes 40m, and GBT radio telescopes, together with SMA+APEX spatially resolved maps. Results. The spectral shape of HC3N lines shows three distinct velocity components: a broad component with a line width of 23 km s−1 (C1), and two narrow components with line widths of 7.2 and 8.8 km s−1 (C2 and C3). This suggests that a fraction of the molecular gas in this cloud is undergoing turbulence dissipation. From an initial local thermodynamic equilibrium analysis, we found column densities of N = (6.54 ± 0.07) × 1014 cm−2, (9 ± 3) × 1014 cm−2, and (3.6 ± 0.7) × 1013 cm−2 for C1, C2, and C3, respectively. These values were used as input for a subsequent non-local thermodynamic equilibrium analysis, in which we found H2 densities of 2 × 104 cm−3, 5 × 104 cm−3, and 4 × 105 cm−3 and kinetic temperatures of 140 K, 30 K, and 80 K for C1, C2, and C3, respectively. The spatially resolved maps confirm that the colder and high-density condensations C2 and C3, which peak in the 70–85 km s−1 velocity range, have deconvolved sizes of 9″ (0.36 pc) and 7.6″ (0.3 pc), respectively, and are embedded in a more diffuse and warmer gas (C1). Conclusions. The larger-scale structure of the Sgr B2 region, consistently with previous works, shows a hole at 40–50 km s−1 that is likely due to a small cloud that shocked the Sgr B2 region and is spatially related with a massive cloud at 60–80 km s−1. We propose that the impacting small cloud sequentially triggered the formation of Sgr B2(M), (N), and (S) and the condensations in G+0.693-0.027 during its passage. The two condensations are in a post-shocked environment that has undergone internal fragmentation. Based on the analysis of their masses and the virial parameters, C2 might expand, while C3 might further fragment or collapse. [ABSTRACT FROM AUTHOR]

Context. Recent spectra of protoplanetary disks around very low-mass stars (VLMS), captured by the Mid-InfraRed Instrument (MIRI) on board the James Webb Space Telescope (JWST), reveal a rich carbon chemistry. Current interpretations of these spectra are based on 0D slab models and provide valuable estimates for molecular emission temperatures and column densities in the innermost disk (radius ≲ 1 au). However, the established fitting procedures and simplified models are challenged by the many overlapping gas features. Aims. We aim to simultaneously determine the molecular and the dust composition of the disk around the VLMS Sz 28 in a Bayesian way. Methods. We modelled the JWST/MIRI spectrum of Sz 28 up to 17 μm using the Dust Continuum Kit with Line emission from Gas (DuCKLinG). Systematically excluding different molecules from the Bayesian analysis allowed for an evidence determination of all investigated molecules and isotopologues. We continued by examining the emission conditions and locations of all molecules, analysing the differences to previous 0D slab fitting, and analysing the dust composition. Results. We find very strong Bayesian evidence for the presence of C2H2, HCN, C6H6, CO2, HC3N, C2H6, C3H4, C4H2, and CH4 in the JWST/MIRI spectrum of Sz 28. Additionally, we identify CH3 and find tentative indications for NH3. There is no evidence for water in the spectrum. However, we show that column densities of up to 2 × 1017 cm−2 could be hidden in the observational noise if assuming similar emission conditions of water as the detected hydrocarbons. Contrary to previous 0D slab results, a C4H2 quasi-continuum is robustly identified. We confirm previous conclusions that the dust in Sz 28 is highly evolved, with large grains (5 μm) and a high crystallinity fraction being retrieved. We expect some of the stated differences to previous 0D slab fitting results to arise from an updated data reduction of the spectrum, but also due to the different modelling process. The latter reason underpins the need for more advanced models and fitting procedures. [ABSTRACT FROM AUTHOR]

Context. Ammonia is detected both in the gas phase and in the ices of protoplanetary disks. However, its gas phase abundances are still difficult to reproduce via chemical modelling when only the thermal-, UV photon-, and cosmic ray-induced processes are considered. Among other non-thermal mechanisms, X-ray photo-desorption is a relevant pathway to maintaining a budget of molecules in the gas of disks. However, no quantitative data are available to constrain its efficiency in the case of ammonia-containing ices. Aims. We studied the desorption induced by soft X-rays from ammonia ices to determine the photo-desorption yields of neutral molecules that can be applied to the conditions of protoplanetary disks. We also aim to identify the desorption mechanisms at play. Methods. Pure ammonia ices were deposited at 23 or 75 K and irradiated between 395 and 435 eV, with monochromatic synchrotron light. Desorption of neutral molecules and fragments was detected using a quadrupole mass spectrometer, calibrated to obtain des-orption yields. These values were extrapolated and the spectrum of a protoplanetary disk was used to extract average astrophysical desorption yields. Results. Photo-desorption from NH3 ices is dominated by the desorption of neutral NH3 and N2 molecules. The desorption mechanism mostly involves the thermalisation of Auger electrons in the ice, although resonant phenomena also contribute near the N 1s ionisation edge. The NH3 photo-desorption is independent of ice morphology and irradiation temperature. Contrary to NH3 desorption, N2 desorption is sensitive to the photon fluence received by the ice. Average photo-desorption yields derived using the TW Hya X-ray spectrum reveal that the NH3 photo-desorption would be four to six times more efficient than that of H2O. This could be at the origin of unexplained high NH3/H2O abundance ratios predicted in the disk around TW Hya. This result ought to be confirmed by the study of mixed water-ammonia ices. [ABSTRACT FROM AUTHOR]

The systematic analysis of the correlations between diffuse interstellar bands (DIBs) is extended to weak DIBs through the comprehensive catalogue of the Apache Peak Observatory (APO) of 559 DIBs in 25 lines of sight with diverse interstellar properties. The main results are the following: 1) An extension of the number of DIBs identified to be related to C2, that is, those that need very shielded interstellar regions for their carriers to survive UV photo-dissociation. Based on the correlations with the reference C2 and ζ DIBs, anticorrelations with UV-favoured (σ) DIBs, and the strength ratios in shielded and unshielded sight lines, we propose 12 new C2 candidates and 34 possible "C2-related" DIBs (mostly at λ <5950 Å) in addition to the ~20 known confirmed C2 DIBs. With these additions, the census of C2 DIBs might approach completion. 2) We discovered that the intensities of a large set of poorly studied DIBs are strongly enhanced in one or two of the sight lines of HD 175156 and HD 148579. This tentative class, denoted χ for the time being, extends over the whole wavelength range of visible DIBs. It might include up to 50–100 members, half at λ > 6000 Å, and a number of C2 DIBs. These possible enhancements might reflect specific formation processes of their carriers that are yet to be identified in the interstellar medium of these two sight lines. The possible matches of the wavelength of five very broad DIBs, including three χ DIBs, with the strong bands that were recently measured by action spectroscopy might favour some long carbon chains and rings as carriers of some DIBs. These correlations and findings justify further theoretical and laboratory efforts for improving our understanding of the complex physics, spectroscopy, and chemistry of the various carbon chains and rings, and their possible formation and destruction in the diffuse interstellar medium. [ABSTRACT FROM AUTHOR]

We investigated the effect of time-dependent ice growth on dust grains on the opacity and hence on the dust temperature in a collapsing molecular cloud core, with the aim of quantifying the effect of the dust temperature variations on ice abundances as well as the evolution of the collapse. To perform the simulations, we employed a one-dimensional collapse model that self-consistently and time-dependently combines hydrodynamics with chemical and radiative transfer simulations. The dust opacity was updated on the fly based on the ice growth as a function of the location in the core. The results of the fully dynamical model were compared against simulations run with different values of fixed ice thickness. We found that the ice thickness increases quickly and reaches a saturation value (as a result of a balance between adsorption and desorption) of approximately 90 monolayers in the central core (volume density ~104 cm−3), and several tens of monolayers at a volume density of ~103 cm−3, after only a few 105 yr of evolution. The results thus exclude the adoption of thin (approximately ten monolayer) ices in molecular cloud simulations except at very short timescales. However, the differences in abundances and the dust temperature between the fully dynamic simulation and those with a fixed dust opacity are small; abundances change between the solutions generally within a factor of two only. The assumptions on the dust opacity do have an effect on the collapse dynamics through the influence of the photoelectric effect on the gas temperature, and the simulations take a different time to reach a common central density. This effect is, however, small as well. In conclusion, carrying out chemical simulations using a dust temperature corresponding to a fixed opacity seems to be a good approximation. Still, although at least in the present case its effect on the overall results is limited – as long as the grains are monodisperse – ice growth should be considered to obtain the most accurate representation of the collapse dynamics. We have found in a previous work that considering a grain size distribution leads to a complicated ice composition that depends on the grain size nonlinearly. With this in mind, we will carry out a follow-up study where the influence of the grain size on the present simulation setup is investigated. [ABSTRACT FROM AUTHOR]

Context. The cosmic-ray ionization rate (ζ2) is one of the key parameters in star formation, since it regulates the chemical and dynamical evolution of molecular clouds by ionizing molecules and determining the coupling between the magnetic field and gas. Aims. However, measurements of ζ2 in dense clouds (e.g., nH ≥ 104 cm−3) are difficult and sensitive to the model assumptions. The aim is to find a convenient analytic approach that can be used in high-mass star-forming regions (HMSFRs), especially for warm gas environments such as hot molecular cores (HMCs). Methods. We propose a new analytic approach to calculate ζ2 through HCO+, N2H+, and CO measurements. By comparing our method with various astrochemical models and with observations found in the literature, we identify the parameter space for which the analytic approach is applicable. Results. Our method gives a good approximation, to within 50%, of ζ2 in dense and warm gas (e.g., nH ≥ 104 cm−3, T = 50, 100 K) for AV ≥ 4 mag and t ≥ 2 × 104 yr at Solar metallicity. The analytic approach gives better results for higher densities. However, it starts to underestimate ζ2 at low metallicity (Z = 0.1 Z⊙) when the value is too high (ζ2 ≥ 3 × 10−15 s−1). By applying our method to the OMC-2 FIR4 envelope and the L1157-B1 shock region, we find ζ2 values of (1.0 ± 0.3) × 10−14 s−1 and (2.2 ± 0.4) × 10−16 s−1, consistent with those previously reported. Conclusions. We calculate ζ2 toward a total of 82 samples in HMSFRs, finding that the average value of ζ2 toward all HMC samples (ζ2 = (7.4±5.0)×10−16 s−1) is more than an order of magnitude higher than the theoretical prediction of cosmic-ray attenuation models, favoring the scenario that locally accelerated cosmic rays in embedded protostars should be responsible for the observed high ζ2. [ABSTRACT FROM AUTHOR]

Context. Photoevaporation is an important process for protoplanetary disc dispersal, but there has so far been a lack of consensus from simulations over the mass-loss rates and the most important part of the high-energy spectrum involved in driving the wind. Aims. We aim to isolate the origins of these discrepancies through carefully benchmarked hydrodynamic simulations of X-ray photoevaporation with time-dependent thermochemistry calculated on the fly. Methods. We conducted hydrodynamic simulations with PLUTO where the thermochemistry is calculated using PRIZMO. We explored the contribution of certain key microphysical processes and the impact of employing different spectra previously used in literature studies. Results. We find that additional cooling results from the excitation of O by neutral H, which leads to dramatically reduced mass-loss across the disc compared to previous X-ray photoevaporation models, with an integrated rate of ~10−9 M⊙ yr−1. Such rates would allow for longer-lived discs than previously expected from population synthesis. An alternative spectrum with less soft X-ray produces mass-loss rates around a factor of two to three times lower. The chemistry is significantly out of equilibrium, with the survival of H2 into the wind being aided by advection. This leads to H2 becoming the dominant coolant at 10s au, thus stabilising a larger radial temperature gradient across the wind as well as providing a possible wind tracer. [ABSTRACT FROM AUTHOR]

Context. As a refractory material, vanadia (solid V2O5) is likely to be found as a condensate in the atmospheres of substellar objects such as exoplanets and brown dwarfs. However, the nature of the nanometer-sized vanadium oxide clusters that partake in the nucleation process is not well understood. Aims. We aim to understand the formation of cloud condensation nuclei in oxygen-rich substellar atmospheres by calculating the relevant fundamental properties of the energetically most favorable vanadium oxide molecules and clusters and, investigate how they contribute to the formation of condensation seeds. Methods. We applied a hierarchical optimization approach in order to find the most favourable structures for clusters of (VO)N and (VO2)N for N = 1−10, and of (V2O5)N for N = 1−4, and to calculate their thermodynamical potentials. The candidate geometries are initially optimized by applying classical interatomic potentials; these are then refined at the B3LYP/cc-pVTZ level of theory to obtain accurate zero-point energies and thermochemical quantities. Results. We present previously unreported vanadium oxide cluster structures as the lowest-energy isomers. Moreover, we report revised cluster energies and their thermochemical properties. Chemical equilibrium calculations are used to assess the impact of the updated and newly derived thermodynamic potentials on the gas-phase abundances of vanadium-bearing species. In chemical equilibrium, larger clusters from different stoichiometric families are found to be the most abundant vanadium-bearing species for temperatures below ~1000 K, while molecular VO is the most abundant between ~1000 K and ~2000 K. We determine the nucleation rates of each stoichiometric family for a given (Tgas, pgas) profile of a brown dwarf using both classical and non-classical nucleation theory. Conclusions. Small differences in the revised Gibbs free energies of the clusters have a large impact on the abundances of vanadium-bearing species in chemical equilibrium at temperatures below ~1000 K. These abundance changes subsequently have an impact on the nucleation rates of each stoichiometric family. We find that with the revised and more accurate cluster data, non-classical nucleation rates are up to 15 orders of magnitude higher than classical nucleation rates. [ABSTRACT FROM AUTHOR]

Fundamental understanding of initial evolutions of molecules in the universe is of great interest and importance. CH4 is one of the abundant simple molecules in the universe. Herein we report γ‐ray, high‐energy photons commonly existing in cosmic rays and unstable isotope decay, as an external energy to efficiently drives aqueous‐phase CH4 conversions to various products with the presence of oxygen at room temperature. Glycine also forms with an additional introduction of ammonia. Both CH4 conversions and product distributions are modified by solid granules, and a CH3COOH selectivity as high as 82 % is obtained when SiO2 is added. Our results point to γ‐ray driven aqueous‐phase CH4 conversions as a likely formation network of initial complex organic compounds in the universe and offer an alternative strategy for efficiently utilizing CH4 as the carbon source to produce value‐added products at mild conditions, a long‐standing challenging task in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Detection of the AlCl molecule in IRC+10216 has been reported in the literature. We here report calculations of reaction rate constants for formation of AlCl through radiative association of Al and Cl for a temperature interval of 1000 to 14000 K. Potential energy and permanent/transition dipole moment curves were taken from the literature. Quantum mechanical and semiclassical/classical methods were used to obtain the reaction cross-sections and thermal rate constants, accounting for shape resonances with Breit–Wigner theory. Both the A |$^1 \Pi \rightarrow$| X |$^1 \Sigma ^+$| transition and the X |$^1 \Sigma ^+\rightarrow$| X |$^1 \Sigma ^+$| transition have been treated, with results showing that the former dominates for the temperatures considered in this study. Our rate constants are a factor of two to three larger than previously calculated values, where the latter were obtained without considering resonances or the X |$^1 \Sigma ^+\rightarrow$| X |$^1 \Sigma ^+$| transition. Our new values do however not change the previous conclusion that radiative association can only contribute modestly to the formation of AlCl under the given conditions. [ABSTRACT FROM AUTHOR]

Forsterite is a primary constituent of interstellar dust and planetary systems. It is believed to originate from the outflows of oxygen-rich stars and undergo further processing within the interstellar medium through the action of cosmic rays and shocks. Under these harsh conditions, point defects may form, such as MgO Schottky vacancies. These vacancies can then undergo atom reconstruction as part of a chemical process to maintain the system's crystalline structure. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously observed interstellar molecules and are thought to form through gas-phase reactions akin to sooting flames. However, their role and impact on dust stability remain unknown. In this study, we employ an atomistic artificial-intelligence-based method, surrogate machine learning trained directly by density functional theory. Specifically, we utilize gofee (global optimization with first-principles energy expressions) to predict possible reconstructions of MgO vacancies on a crystalline forsterite (010) surface as an important component of interstellar dust and planetary systems. We identify nine possible reconstructions involving the formation of unbound Si and O atoms. We investigate their energy stability and find that the reconstruction of Si–O atoms stabilizes the vacancy by about 0.54 eV. Additionally, if PAHs bind with the unbound O and Si atoms of the vacancy, the vacancy is stabilized by approximately 1.76 eV. We demonstrate that PAHs, along with the reconstruction of unbound atoms on the dust surface, affect the stability of the dust, which might open up avenues for diverse chemistry. [ABSTRACT FROM AUTHOR]

We present high-spatial resolution (0.7–1.0 arcsec) submillimeter observations of continuum and molecular lines of CH |$_{3}$| OCHO, CH |$_{3}$| OCH |$_{3}$|⁠ , and H |$_{2}$| CCO toward 11 high-mass star-forming regions using the Atacama large millimetre/submillimetre array (ALMA). A total of 19 separate cores from nine high-mass star-forming regions are found to be line-rich, including high-, intermediate-, and low-mass line-rich cores. The three molecules are detected in these line-rich cores. We map the emission of CH |$_{3}$| OCHO, CH |$_{3}$| OCH |$_{3}$|⁠ , and H |$_{2}$| CCO in nine high-mass star-forming regions. The spatial distribution of the three molecules is very similar and concentrated in the areas of intense continuum emission. We also calculate the rotation temperatures, column densities, and abundances of CH |$_{3}$| OCHO, CH |$_{3}$| OCH |$_{3}$|⁠ , and H |$_{2}$| CCO under the local thermodynamic equilibrium assumption. The abundances relative to H |$_{2}$| and CH |$_{3}$| OH, and line widths of the three molecules are significantly correlated. The abundances relative to H |$_{2}$|⁠ , temperatures, and line widths of the three molecules tend to be higher in cores with higher mass and outflows detected. The possible chemical links of the three molecules are discussed. [ABSTRACT FROM AUTHOR]

Gas-phase abundance ratios between C2H4O2 isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed toward a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated C2H4O2 abundances. A combination of high gas densities and long timescales during ice-mantle desorption (∼125–160 K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of "complex organic molecule" (COM) production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk. [ABSTRACT FROM AUTHOR]

The chemistry of phosphorus (31P) in space is particularly significant due to the key role it plays in biochemistry on Earth. Utilising radio and infrared spectroscopic observations, several key phosphorus-containing molecules have been detected in interstellar clouds, circumstellar shells, and even extragalactic sources. Among these, phosphorus nitride (PN) was the first P-bearing molecule detected in space, and still is the species detected in the largest number of sources. Phosphorus oxide (PO) and phosphine (PH3) were also crucial species due to their role both in chemical networks and in forming biogenic compounds. The still limited high-angular resolution observations performed so far are shading light on the geometrical distribution of these molecules, which represent crucial insights on their formation processes. Observations have also highlighted the challenges and complexities associated with detecting and understanding phosphorus chemistry in space, owing to the low elemental abundance of P relative to other elements. This review article provides a state-of-art picture of the observational results obtained so far on phosphorus compounds in the interstellar medium. Special attention is given to star- forming regions, and to their implications for our understanding of prebiotic chemistry and the potential for life beyond Earth. Our knowledge of the dominant formation and destruction pathways of the most abundant species has improved, but critical questions remain open, among which: what is (are) the main phosphorus carrier(s) in space? Upcoming new facilities are expected to contribute significantly to this field, offering opportunities to both detect new phosphorus-bearing molecules and enlarge the number of sources in which the chemistry of P can be studied. The synergy between observations, theoretical models, laboratory experiments, and computational chemistry is mandatory to significantly progress in our comprehension of the chemistry of this important but poorly studied chemical element. [ABSTRACT FROM AUTHOR]

The detection of various molecular species, including complex organic molecules relevant to biochemical and geochemical processes, in astronomical settings, such as the interstellar medium or the outer solar system, has led to the increased need for a better understanding of the chemistry occurring in these cold regions of space. In this context, the chemistry of ices prepared and processed at cryogenic temperatures has proven to be of particular interest due to the fact that many interstellar molecules are believed to originate within the icy mantles adsorbed on nano- and micro-scale dust particles. The chemistry leading to the formation of such molecules may be initiated by ionizing radiation in the form of galactic cosmic rays or stellar winds, and thus, there has been an increased interest in commissioning experimental setups capable of simulating and better characterizing this solid-phase radiation astrochemistry. In this article, we describe a new facility called AQUILA (Atomki-Queen's University Ice Laboratory for Astrochemistry), which has been purposefully designed to study the chemical evolution of ices analogous to those that may be found in the dense interstellar medium or the outer solar system as a result of their exposure to keV ion beams. The results of some ion irradiation studies of CH3OH ice at 20 K are discussed to exemplify the experimental capabilities of the AQUILA as well as to highlight its complementary nature to another laboratory astrochemistry setup at our institute. [ABSTRACT FROM AUTHOR]

Ice mantles play a crucial role in shaping the astrochemical inventory of molecules during star and planet formation. Small-scale molecular processes have a profound impact on large-scale astronomical evolution. The areas of solid-state laboratory astrophysics and computational chemistry involve the study of these processes. We review laboratory efforts in ice spectroscopy, methodological advances and challenges, and laboratory and computational studies of ice physics and ice chemistry. We place the last of these in context with ice evolution from clouds to disks. Three takeaway messages from this review are: Laboratory and computational studies allow interpretation of astronomical ice spectra in terms of identification, ice morphology, and local environmental conditions as well as the formation of the involved chemical compounds. A detailed understanding of the underlying processes is needed to build reliable astrochemical models to make predictions about abundances in space. The relative importance of the different ice processes studied in the laboratory and computationally changes during the process of star and planet formation. [ABSTRACT FROM AUTHOR]

The identification of complex pre-biotic molecules using millimetre and submillimetre telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium, ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (⁠|${\rm CH}_{2}{\rm OHCHO}$|⁠). We present the detection of the rotational emission lines of |$aGg^{\prime }$| conformer of ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array. The estimated column density of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the G358.93–0.03 MM1 is (4.5 |$\pm 0.1)\times 10^{16}$| cm |$^{-2}$| with an excitation temperature of 155 |$\pm$| 35 K. The abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm H}_{2}$| is (1.4 |$\pm 0.5)\times 10^{-8}$|⁠. Similarly, the abundances of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm CH}_{2}{\rm OHCHO}$| and |${\rm CH}_{3}{\rm OH}$| are 3.1 |$\pm$| 0.5 and (6.1 |$\pm 0.3)\times 10^{-3}$|⁠. We compare the estimated abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with the existing three-phase warm-up chemical model abundance of |$({\rm CH}_2{\rm OH})_{2}$|⁠ , and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the hot molecular cores, and we find that |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| is probably created via the recombination of two |${\rm CH}_{2}{\rm OH}$| radicals on the grain surface of G358.93–0.03 MM1. [ABSTRACT FROM AUTHOR]

The recent detection of ethanolamine (EtA, HOCH |$_2$| CH |$_2$| NH |$_2$|⁠), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (H |$_2$| O) ice, to electron, ion, and thermal processing, representing 'energetic' mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy, we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of H |$_2$| O:EtA mixed ice obtained after 1 MeV He |$^+$| ion irradiation have been collected at different doses. The main radiolysis products, including H |$_2$| O, CO, CO |$_2$|⁠ , NH |$_3$|⁠ , and CH |$_3$| OH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He |$^+$| ion irradiation of pure EtA and H |$_2$| O:EtA mixed ice are derived to range between |$10.8\!-\!26.3$|  eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in H |$_2$| O ice is more stable than in pure form and it should survive throughout the star and planet formation process. [ABSTRACT FROM AUTHOR]

The reservoir of sulphur accounting for sulphur depletion in the gas of dense clouds and circumstellar regions is still unclear. One possibility is the formation of sulphur chains, which would be difficult to detect by spectroscopic techniques. This work explores the formation of sulphur chains experimentally, both in pure H |$_2$| S ice samples and in H |$_2$| O:H |$_2$| S ice mixtures. An ultrahigh vacuum chamber, ISAC, eqquipped with FTIR and QMS, was used for the experiments. Our results show that the formation of H |$_2$| S |$_x$| species is efficient, not only in pure H |$_2$| S ice samples, but also in water-rich ice samples. Large sulphur chains are formed more efficiently at low temperatures (⁠|$\approx$| 10 K), while high temperatures (⁠|$\approx$| 50 K) favour the formation of short sulphur chains. Mass spectra of H |$_2$| S |$_x$|⁠ , x = 2–6, species are presented for the first time. Their analysis suggests that H |$_2$| S |$_x$| species are favoured in comparison with S |$_x$| chains. Nevertheless, the detection of several S |$_x^+$| fragments at high temperatures in H |$_2$| S:H |$_2$| O ice mixtures suggests the presence of S |$_8$| in the irradiated ice samples, which could sublimate from 260 K. ROSINA instrument data from the cometary Rosetta mission detected mass-to-charge ratios 96 and 128. Comparing these detections with our experiments, we propose two alternatives: (1) H |$_2$| S |$_4$| and H |$_2$| S |$_5$| to be responsible of those S |$_3^+$| and S |$_4^+$| cations, respectively, or (2) S |$_8$| species, sublimating and being fragmented in the mass spectrometer. If S |$_8$| is the parent molecule, then S |$_5^+$| and S |$_6^+$| cations could be also detected in future missions by broadening the mass spectrometer range. [ABSTRACT FROM AUTHOR]

In comets and in the cold phase of the interstellar medium (ISM), ammonium salts are key molecular species due to their role in the retention of volatile compounds on cold surfaces. In the case of sulphur, the H |$_2$| S/OCS ratio observed in protostars could be explained by the presence of ammonium hydrosulphide (NH |$_4$| SH) salts. However, laboratory data on the properties of NH4SH in ISM cold relevant conditions are rather scarce, as they usually focus on the atmosphere of Jupiter. We propose to consolidate the laboratory data regarding NH |$_4$| SH on grains, by performing temperature programmed desorption experiments and Fourier transform infrared reflection spectroscopy. The salt was also exposed to H atoms to mimic the ISM conditions. NH |$_4$| SH was found to form in situ at 10 K, from a mixture of ammonia (NH |$_3$|⁠) and hydrogen sulphide (H |$_2$| S). The NH |$_4^+$| infrared feature (1485 cm |$^{-1}$|⁠) is the most prominent one at 80 K. As pure species, H |$_2$| S and NH |$_3$| desorb at 76 and 90 K, respectively, whereas they are released into the gas phase at 153 K when adsorbed in the form of salt. The presence of water delays the desorption of the salt until the very end of the water desorption, but does not affect the desorption kinetics. During H-exposure, the salt is dissociated and no new product was detected. As a comparative study, salts have been included in the Nautilus gas–grain model. The results show a good correlation with the observations of IRAS 16293−2422B, as opposed to when NH |$_4$| SH is not included in the model. [ABSTRACT FROM AUTHOR]

Interstellar anions play an important role in astrochemistry as being tracers of the physical and chemical conditions in cold molecular clouds and circumstellar gas. The local thermodynamic equilibrium is generally not fulfilled in media where anions are detected and radiative and collisional data are required to model the observed lines. The C2H− anion has not yet been detected in the interstellar medium; however, collisional data could be used for non-LTE models that would help in identifying the most intense lines. For this purpose, we have computed the first 4D potential energy surface (PES) of the C2H−–H2 complex using an explicitly correlated coupled-cluster approach. The PES is characterized by a single deep minimum with a well-depth of 924.96 cm−1. From this interaction potential, we derived excitation cross sections and rate coefficients of C2H− induced by collisions with para- and ortho-H2. The results obtained for collisions with para-H2 are compared to previous calculations performed using a 2D-PES obtained from an average over H2 rotations. [ABSTRACT FROM AUTHOR]

We here review mostly experimental and some computational work devoted to nucleation in amorphous ices. In fact, there are only a handful of studies in which nucleation and growth in amorphous ices are investigated as two separate processes. In most studies, crystallization temperatures Tx or crystallization rates RJG are accessed for the combined process. Our Review deals with different amorphous ices, namely, vapor-deposited amorphous solid water (ASW) encountered in many astrophysical environments; hyperquenched glassy water (HGW) produced from μm-droplets of liquid water; and low density amorphous (LDA), high density amorphous (HDA), and very high density amorphous (VHDA) ices produced via pressure-induced amorphization of ice I or from high-pressure polymorphs. We cover the pressure range of up to about 6 GPa and the temperature range of up to 270 K, where only the presence of salts allows for the observation of amorphous ices at such high temperatures. In the case of ASW, its microporosity and very high internal surface to volume ratio are the key factors determining its crystallization kinetics. For HGW, the role of interfaces between individual glassy droplets is crucial but mostly neglected in nucleation or crystallization studies. In the case of LDA, HDA, and VHDA, parallel crystallization kinetics to different ice phases is observed, where the fraction of crystallized ices is controlled by the heating rate. A key aspect here is that in different experiments, amorphous ices of different "purities" are obtained, where "purity" here means the "absence of crystalline nuclei." For this reason, "preseeded amorphous ice" and "nuclei-free amorphous ice" should be distinguished carefully, which has not been done properly in most studies. This makes a direct comparison of results obtained in different laboratories very hard, and even results obtained in the same laboratory are affected by very small changes in the preparation protocol. In terms of mechanism, the results are consistent with amorphous ices turning into an ultraviscous, deeply supercooled liquid prior to nucleation. However, especially in preseeded amorphous ices, crystallization from the preexisting nuclei takes place simultaneously. To separate the time scales of crystallization from the time scale of structure relaxation cleanly, the goal needs to be to produce amorphous ices free from crystalline ice nuclei. Such ices have only been produced in very few studies. [ABSTRACT FROM AUTHOR]

The molecular phase of supernova-driven outflows originates from the cold, molecular gas in the disc of a star-forming galaxy, and may carry a substantial fraction of the wind mass flux in some galaxies, but it remains poorly understood. Observations of this phase come mostly from very nearby galaxies due its low-surface brightness and covering fraction, and simulations often lack the spatial resolution necessary to resolve it. Here, we analytically estimate the survivability of this phase in order to understand under what conditions a galactic wind can contain a significant molecular phase. We show that the molecular content of outflows is primarily determined by two dimensionless numbers: a generalized Eddington ratio describing the strength of the outflow and the dissociation parameter, an ionization parameter-like quantity describing the strength of the radiation field per baryon. We apply this model to a sample of galaxies and show that, while any molecules entrained in the winds of normal star-forming galaxies should be destroyed close to the galactic disc, the outflows of strong starburst should become increasingly dominated by molecules. [ABSTRACT FROM AUTHOR]

In this work, the gas-phase ion–atom collision reaction between large cationic carbon clusters and H-atoms is investigated. The carbon cluster cations (C |$_{48-2*n}$| |$^+$|⁠ , n = [0 |$-$| 8]) are produced from the photo-fragmentation processes of large PAH (dicoronylene, DC, C |$_{48}$| H |$_{20}$|⁠) cations. The hydrogenated carbon cluster cations are efficiently formed (e.g. C |$_{44/46}$| H |$_{9}$| |$^+$|⁠), and no even–odd hydrogenated mass patterns are observed. The hydrogenation behaviour and hydrogenation rate for these carbon cluster cations are the same. With theoretical calculations, the formation and bending processes of carbon cluster cations, the structure of these newly formed hydrogenated carbon cluster cations, and the bonding energies for the hydrogenation pathways are investigated. During the formation process of carbon clusters, the zigzagged edges gradually increase, and the planar configuration tends towards a bent and folded molecular configuration, i.e. from graphene to fullerene structures. The bending process with higher exothermic energies provides a reasonable explanation for the formation of the 'magic numbers' (e.g. C-atoms = 44) carbon clusters and their greater stability. The exothermic energy for each hydrogenation reaction pathway is relatively high; consequently, the forms and the hydrogenated states of carbon clusters are complex. The hydrogenation ability of edge carbon sites is higher than that of internal carbon sites; after bending and folding, the hydrogenation ability of these originally internal carbon sites becomes higher due to structural caged. As a result, under the co-evolution interstellar chemistry network, the (hydrogenation) states and forms of carbon compounds are complicated and diverse in the ISM. [ABSTRACT FROM AUTHOR]

In this paper, we provide a highly accurate value for the binding energy of benzene to proton-ordered crystalline water ice (XIh), as a model for interstellar ices. We compare our computed value to the latest experimental data available from temperature-programmed desorption experiments and find that our binding energy value agrees well with data obtained from binding to either crystalline or amorphous ice. Importantly, our new value is lower than that used in most astrochemical networks by about nearly half its value. We explore the impact of this revised binding energy value for both an asymptotic giant branch (AGB) outflow and a protoplanetary disc. We find that the lower value of the binding energy predicted here compared with values used in the literature (4050 K versus 7587 K) leads to less depletion of gas-phase benzene in an AGB outflow, and leads to a shift outwards in the benzene snowline in the mid-plane of a protoplanetary disc. Using this new value, the AGB model predicts lower abundances of benzene in the solid phase throughout the outflow. The disc model also predicts a larger reservoir of gas-phase benzene in the inner disc, which is consistent with the recent detections of benzene for the first time in protoplanetary discs with JWST. [ABSTRACT FROM AUTHOR]

The present survey represents a continuation of our study of high mass star forming regions in the lines of deuterated molecules, the first results of which were published in [1]. This paper present the results of observations of 50 objects in the line of ortho modification of singly deuterated ammonia NH2D at a frequency of 85.9 GHz, carried out using the 20-m radio telescope of the Onsala Space Observatory (Sweden). This line is detected in 29 sources. The analysis of obtained data, as well as the fact that the gas density in the investigated sources, according to independent estimates, is significantly lower than the critical density for this NH2D transition, indicate non-LTE excitation of NH2D. Based on non-LTE modeling, estimates of the relative content of the NH2D molecule and the degree of deuterium enrichment were obtain, and the dependencies of these parameters on temperature and velocity dispersion were analyzed with and without taking into account detection limits assuming the same gas density in all sources. An anti-correlation between the NH2D relative abundances and the kinetic temperature is revealed in a temperature range of 15–50 K. At the same time, a significant decrease in the ratio of the NH2D/NH3 abundances with increasing temperature, predicted by the available chemical models, is not observed under the adopted assumptions. An anti-correlation was also revealed between the relative content of the main isotopologue of ammonia NH and the velocity dispersion, while no statistically significant correlation with the kinetic temperature of sources in the same temperature range was found. [ABSTRACT FROM AUTHOR]

In this paper, we present a bibliometric analysis of the Periodic Table. We have conducted a comprehensive analysis of Scopus based database using the keyword "Mendeleev Periodic Table". Our findings suggest that the Periodic Table is an influential topic in the field of Inorganic as well as Organic Chemistry. Areas for future research could include on expanding our analysis to include other bibliometric indicators to gain a more comprehensive understanding of the impact of the Periodic Table in the chemistry-based scientific investigations and even in the field of astrochemistry, which explores chemical processes in space, is intricately linked to fundamental chemistry. In this context, the quote of Carl Sagan is relevant where he eloquently expressed an inherent connection between chemistry and astrophysics: "The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars." In the ongoing study we have presented a ground level investigation of the conjecture of Sagan via Periodic Table based on bibliometric analysis whereas in the next level our aim is to present the stellar connection of it through Hertzsprung-Russel diagram as well as cluster of stars. The Periodic Table holistically serves as a foundational platform for understanding chemical elements both on the Earth and in celestial bodies. The present investigation fundamentally identifies the main working field of research and lays the groundwork for potential connections to astrochemical studies. [ABSTRACT FROM AUTHOR]