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Line intensity mapping (LIM) serves as a potent probe in astrophysics, relying on the statistical analysis of integrated spectral line emissions originating from distant star-forming galaxies. While LIM observations hold the promise of achieving a broad spectrum of scientific objectives, a significant hurdle for future experiments lies in distinguishing the targeted spectral line emitted at a specific redshift from undesired line emissions originating at different redshifts. The presence of these interloping lines poses a challenge to the accuracy of cosmological analyses. In this study, we introduce a novel approach to quantify line–line cross-correlations (LIM-LLX), enabling us to investigate the target signal amid instrumental noise and interloping emissions. For example, at a redshift of z ∼ 3.7, we observed that the measured auto-power spectrum of C ii 158 exhibited substantial bias, from interloping line emission. However, cross-correlating C ii 158 with CO(6–5) lines using an FYST-like experiment yielded a promising result, with a signal-to-noise ratio of ∼10. This measurement is notably unbiased. Additionally, we explore the extensive capabilities of cross-correlation by leveraging various CO transitions to probe the tomographic Universe at lower redshifts through LIM-LLX. We further demonstrate that incorporating low-frequency channels, such as 90 and 150 GHz, into FYST's EoR-Spec-like experiment can maximize the potential for cross-correlation studies, effectively reducing the bias introduced by instrumental noise and interlopers. [ABSTRACT FROM AUTHOR]

Line intensity mapping (LIM) can provide a powerful means to constrain the theory of gravity and the nature of dark energy at low and high redshifts by mapping the large-scale structure over many redshift epochs. In this paper, we investigate the potential of the next generation ground-based millimeter-wavelength LIM surveys in constraining several models beyond ΛCDM, involving either a dynamic dark energy component or modifications of the theory of gravity. Limiting ourselves to two-point clustering statistics, we consider the measurements of auto-spectra of several CO rotational lines (from J = 2−1 to J = 6−5) and the [C ii ] fine structure line in the redshift range of 0.25 < z < 12. We consider different models beyond ΛCDM, each one with different signatures and peculiarities. Among them, we focus on Jordan–Brans–Dicke and axion-driven early dark energy models as examples of well-studied scalar-tensor theories acting at late and early times, respectively. Additionally, we consider three phenomenological models based on an effective description of gravity at cosmological scales. We show that LIM surveys deployable within a decade (with ∼108 spectrometer hours) have the potential to improve upon the current bounds on all considered models significantly. The level of improvements range from a factor of a few to an order of magnitude. [ABSTRACT FROM AUTHOR]

Mapping of multiple lines such as the fine-structure emission from [C ii ] (157.7 μ m), [O iii ] (52 and 88.4 μ m), and rotational emission lines from CO are of particular interest for upcoming line intensity mapping (LIM) experiments at millimeter wavelengths, due to their brightness features. Several upcoming experiments aim to cover a broad range of scientific goals, from detecting signatures of the epoch of reionization to the physics of star formation and its role in galaxy evolution. In this paper, we develop a semianalytic approach to modeling line strengths as functions of the star formation rate (SFR) or infrared luminosity based on observations of local and high- z galaxies. This package, LIMpy (Line Intensity Mapping in Python), estimates the intensity and power spectra of [C ii ], [O iii ], and CO rotational transition lines up to the J levels (1–0) to (13–12) based both on analytic formalism and on simulations. We develop a relation among halo mass, SFR, and multiline intensities that permits us to construct a generic formula for the evolution of several line strengths up to z ∼ 10. We implement a variety of star formation models and multiline luminosity relations to estimate the astrophysical uncertainties on the intensity power spectrum of these lines. As a demonstration, we predict the signal-to-noise ratio of [C ii ] detection for an EoR-Spec-like instrument on the Fred Young Submillimeter Telescope. Furthermore, the ability to use any halo catalog allows the LIMpy code to be easily integrated into existing simulation pipelines, providing a flexible tool to study intensity mapping in the context of complex galaxy formation physics. [ABSTRACT FROM AUTHOR]

Deuterium fractionation in molecules is known as one of the most powerful tools to study chemical processes during star and planet formation. Among various interstellar molecules, methanol often shows very high deuterium fractionation. It is the most abundant saturated organic molecule and is known as a parent species to form more complex organic molecules. However, deriving the abundance of deuterated methanol suffers from the uncertainty in the intrinsic line intensities (S μ 2) of CH3OH isotopologues. Due to their floppy nature, theoretical evaluation of the S μ 2 values is not straightforward, particularly for asymmetric-top asymmetric-frame isotopologues such as CH2DOH. In this study, we have measured the line frequencies and their intensities for CH2DOH in the millimeter-wave region from 216 to 264 GHz by using an emission-type millimeter and submillimeter-wave spectrometer. For the a -type J = 5 − 4 transition, the derived S μ 2 values are 13%–27% larger than those theoretically calculated, except for the transitions of K a = 2 for e 0 and K a = 1 for e 1 affected by avoided level crossing. For b -type transitions, significant systematic differences are found between theoretical and experimental S μ 2 values. The results of the present study enable us to accurately derive from observations the CH2DOH abundances, which are essential for understanding deuterium fractionation in various sources. [ABSTRACT FROM AUTHOR]

Using the photon-ion merged-beams technique at a synchrotron light source, we have measured relative cross sections for single and up to five-fold photoionization of Fe2+ ions in the energy range of 690-920 eV. This range contains thresholds and resonances associated with ionization and excitation of 2p and 2s electrons. Calculations were performed to simulate the total absorption spectra. The theoretical results show very good agreement with the experimental data, if overall energy shifts of up to 2.5 eV are applied to the calculated resonance positions and assumptions are made about the initial experimental population of the various levels of the Fe2+([Ar]3d6) ground configuration. Furthermore, we performed extensive calculations of the Auger cascades that result when an electron is removed from the 2p subshell of Fe2+. These computations lead to a better agreement with the measured product-charge-state distributions as compared to earlier work. We conclude that the L-shell absorption features of low-charged iron ions are useful for identifying gas-phase iron in the interstellar medium and for discriminating against the various forms of condensed-phase iron bound to composite interstellar dust grains.

Line intensity mapping (LIM) serves as a potent probe in astrophysics, relying on the statistical analysis of integrated spectral line emissions originating from distant star-forming galaxies. While LIM observations hold the promise of achieving a broad spectrum of scientific objectives, a significant hurdle for future experiments lies in distinguishing the targeted spectral line emitted at a specific redshift from undesired line emissions originating at different redshifts. The presence of these interloping lines poses a challenge to the accuracy of cosmological analyses. In this study, we introduce a novel approach to quantify line–line cross-correlations (LIM-LLX), enabling us to investigate the target signal amid instrumental noise and interloping emissions. For example, at a redshift of z ∼ 3.7, we observed that the measured auto-power spectrum of C ii 158 exhibited substantial bias, from interloping line emission. However, cross-correlating C ii 158 with CO(6–5) lines using an FYST-like experiment yielded a promising result, with a signal-to-noise ratio of ∼10. This measurement is notably unbiased. Additionally, we explore the extensive capabilities of cross-correlation by leveraging various CO transitions to probe the tomographic Universe at lower redshifts through LIM-LLX. We further demonstrate that incorporating low-frequency channels, such as 90 and 150 GHz, into FYST’s EoR-Spec-like experiment can maximize the potential for cross-correlation studies, effectively reducing the bias introduced by instrumental noise and interlopers.

Weak-line quasars (WLQs) are a notable group of active galactic nuclei (AGNs) that show unusually weak UV lines even though their optical-UV continuum shapes are similar to those of typical quasars. The physical mechanism for WLQs is an unsolved puzzle in the AGN unified model. We explore the properties of UV emission lines by performing extensive photoionization calculations based on Cloudy simulations with different spectral energy distributions (SEDs) of AGNs. The AGN continua are built from several observational empirical correlations, where the blackbody emission from the cold disk, the power-law emission from the hot corona, and a soft X-ray excess component are considered. We find that the equivalent width (EW) of C iv from our models is systematically lower than observational values if the component of soft X-ray excess is neglected. The EW will increase several times and is roughly consistent with the observations after considering the soft X-ray excess component as constrained from normal type I AGNs. We find that the UV lines are weak for QSOs with quite large black hole mass (e.g., M _BH > 10 ^9 M _⊙ ) and weak soft X-ray emission due to the deficit of ionizing photons. As an example, we present the strength of C iv based on the multiband SEDs for three nearby weak-line AGNs, where the weaker soft X-ray emission normally predicts the weaker lines.

High-resolution spectra observed by the Solar X-ray spectrometer on board the Hinotori mission are revisited. Flat crystals slightly offset to the satellite spin axis produce automatic spectral scans for emission lines emerging from highly charged iron ions in solar flares every half-spin time period. All the downlinked data of the mission are converted to FITS format and major flare spectral data are revived as IDL save files in ISAS/DARTS. Based on these data sets, single-temperature fits are performed for the emission line complex of highly charged iron ions in the wavelength range of 1.75–1.95 Å and compared with theoretical predictions. Synthetic spectra with single electron temperatures estimated from j / w line-intensity ratios fit fairly well for Fe xxiv and Fe xxiii lines in the wavelength range of 1.85–1.88 Å, while intensity ratios of Fe xxv lines ( x , y , z ) and the inner-shell excitation line of Fe xxiv ( q ) to the Fe xxv resonance line ( w ) have systematic excesses. Empirical relations for the observed line ratios are derived. Ion fractions of Fe ^+25 /Fe ^+24 estimated by intensity ratios of Ly α /w in the temperature range of log T _e =7.25–7.45 are consistent with values in ionization equilibrium, and the remaining excesses of the Fe xxv line ratios may suggest problems with the atomic parameters or atomic modeling.

The initial density distribution provides a basis for understanding the complete evolution of cosmological density fluctuations. While reconstruction in our local Universe exploits the observations of galaxy surveys with large volumes, observations of high-redshift galaxies are performed with a small field of view and therefore can hardly be used for reconstruction. Here, we propose reconstructing the initial density field using the H i 21 cm and CO line intensity maps from the epoch of reionization. Observations of these two intensity maps provide complementary information on the density field—the H i 21 cm field is a proxy of matter distributions in the neutral regions, while the CO line intensity maps are sensitive to the high-density, star-forming regions that host the sources for reionization. Technically, we employ the conjugate gradient method and develop the machinery for minimizing the cost function for the intensity mapping observations. Analytical expressions for the gradient of cost function are derived explicitly. We show that the resimulated intensity maps match the input maps of mock observations using semi-numerical simulations of reionization with an rms error ≲7% at all stages of reionization. This reconstruction is also robust with an rms error of ∼10% when an optimistic level of shot noise is applied to the CO map or white noise at the level of ≲10% of the standard deviation is applied to each map. Our proof-of-concept work demonstrates the robustness of the reconstruction method, thereby providing an effective technique for reconstructing the cosmological initial density distribution from high-redshift observations.

Line intensity mapping (LIM) can provide a powerful means to constrain the theory of gravity and the nature of dark energy at low and high redshifts by mapping the large-scale structure over many redshift epochs. In this paper, we investigate the potential of the next generation ground-based millimeter-wavelength LIM surveys in constraining several models beyond ΛCDM, involving either a dynamic dark energy component or modifications of the theory of gravity. Limiting ourselves to two-point clustering statistics, we consider the measurements of auto-spectra of several CO rotational lines (from J = 2−1 to J = 6−5) and the [C ii ] fine structure line in the redshift range of 0.25 < z < 12. We consider different models beyond ΛCDM, each one with different signatures and peculiarities. Among them, we focus on Jordan–Brans–Dicke and axion-driven early dark energy models as examples of well-studied scalar-tensor theories acting at late and early times, respectively. Additionally, we consider three phenomenological models based on an effective description of gravity at cosmological scales. We show that LIM surveys deployable within a decade (with ∼10 ^8 spectrometer hours) have the potential to improve upon the current bounds on all considered models significantly. The level of improvements range from a factor of a few to an order of magnitude.

The study of the absolute line intensities in the high-resolution spectrum of the D234S molecule in the range of 2300–2900 cm–1 has been carried out for the first time. As a result of our analysis, about 800 experimental intensities of vibrational-rotational transitions have been obtained for the v1 + v2 and v2 + v3 bands, and a set of 6 parameters of the effective dipole moment has been calculated, which reproduce the initial experimental line intensities with standard deviation drms = 9.7%. A list of transitions with frequencies and line intensities in the range under study has been compiled. [ABSTRACT FROM AUTHOR]

The KAPPA package is designed for calculations of optically thin spectra for the non-Maxwellian κ -distributions. This paper presents an extension of the database to allow calculations of the spectra for extreme values of κ < 2, which are important for accurate diagnostics of the κ -distributions in the outer solar atmosphere. In addition, two improvements were made to the ionization equilibrium calculations within the database. First, the ionization equilibrium calculations now include the effects of electron impact multi-ionization (EIMI). Although relatively unimportant for Maxwellian distribution, EIMI becomes important for some elements, such as Fe and low values of κ , where it modifies the ionization equilibrium significantly. Second, the KAPPA database now includes the suppression of dielectronic recombination at high electron densities, evaluated via the suppression factors. We find that at the same temperature, the suppression of dielectronic recombination is almost independent of κ . The ionization equilibrium calculations for the κ -distributions are now provided for a range of electron densities.

Mapping of multiple lines such as the fine-structure emission from [C ii ] (157.7 μ m), [O iii ] (52 and 88.4 μ m), and rotational emission lines from CO are of particular interest for upcoming line intensity mapping (LIM) experiments at millimeter wavelengths, due to their brightness features. Several upcoming experiments aim to cover a broad range of scientific goals, from detecting signatures of the epoch of reionization to the physics of star formation and its role in galaxy evolution. In this paper, we develop a semianalytic approach to modeling line strengths as functions of the star formation rate (SFR) or infrared luminosity based on observations of local and high- z galaxies. This package, LIMpy (Line Intensity Mapping in Python), estimates the intensity and power spectra of [C ii ], [O iii ], and CO rotational transition lines up to the J levels (1–0) to (13–12) based both on analytic formalism and on simulations. We develop a relation among halo mass, SFR, and multiline intensities that permits us to construct a generic formula for the evolution of several line strengths up to z ∼ 10. We implement a variety of star formation models and multiline luminosity relations to estimate the astrophysical uncertainties on the intensity power spectrum of these lines. As a demonstration, we predict the signal-to-noise ratio of [C ii ] detection for an EoR-Spec-like instrument on the Fred Young Submillimeter Telescope. Furthermore, the ability to use any halo catalog allows the LIMpy code to be easily integrated into existing simulation pipelines, providing a flexible tool to study intensity mapping in the context of complex galaxy formation physics.

Deuterium fractionation in molecules is known as one of the most powerful tools to study chemical processes during star and planet formation. Among various interstellar molecules, methanol often shows very high deuterium fractionation. It is the most abundant saturated organic molecule and is known as a parent species to form more complex organic molecules. However, deriving the abundance of deuterated methanol suffers from the uncertainty in the intrinsic line intensities ( S μ ^2 ) of CH _3 OH isotopologues. Due to their floppy nature, theoretical evaluation of the S μ ^2 values is not straightforward, particularly for asymmetric-top asymmetric-frame isotopologues such as CH _2 DOH. In this study, we have measured the line frequencies and their intensities for CH _2 DOH in the millimeter-wave region from 216 to 264 GHz by using an emission-type millimeter and submillimeter-wave spectrometer. For the a -type J = 5 − 4 transition, the derived S μ ^2 values are 13%–27% larger than those theoretically calculated, except for the transitions of K _a = 2 for e _0 and K _a = 1 for e _1 affected by avoided level crossing. For b -type transitions, significant systematic differences are found between theoretical and experimental S μ ^2 values. The results of the present study enable us to accurately derive from observations the CH _2 DOH abundances, which are essential for understanding deuterium fractionation in various sources.

We have determined absorption oscillator strengths for rotational transitions of the C ^2 Π(0)- A ^2 Σ ^+ (0) band of NO, which has been detected in the upper atmosphere of Venus. The molecular quantum defect orbital method has been used in the calculation of the electronic transition moment and the Rydberg–valence interaction between the C ^2 Π( v = 0) and the B ^2 Π ( v = 7) states has been considered. Considerable deviations from normal intensity distribution of the rotational lines have been found at J ≤ 5.5. As far as we know, the present line f -values are reported here for the first time. These data may be useful in the interpretation of the observations obtained by the Visible and Infrared Thermal Imaging Spectrometer instrument on the Venus Express spacecraft.

Deuterium (D) was exclusively generated in the Big Bang, and the standard Big Bang nucleosynthesis (BBN) model predicts a primordial abundance of D/H ≈ 26 parts per million (ppm). As the Galaxy evolves, D/H gradually decreases because of astration. The Galactic chemical evolution (GCE) model predicts a present-day abundance of D/H ≳ 20 ppm. However, observations of the local interstellar medium have revealed that the gas-phase interstellar D/H varies considerably from one region to another and has a median abundance of D/H ≈ 13 ppm, substantially lower than predicted from the BBN and GCE models. It has been suggested that the missing D atoms of D/H ≈ 7 ppm could have been locked up in deuterated polycyclic aromatic hydrocarbon (PAH) molecules. However, we have previously demonstrated that PAHs with aromatic C–D units are insufficient to account for the missing D. Here we explore if PAHs with aliphatic C–D units could be a reservoir of D. We perform quantum chemical computations of the vibrational spectra of superdeuterated PAHs (in which one D and one H share one C atom) and PAHs to which a D-substituted methyl group is attached, and derive the band strengths of the aliphatic C–D stretch ( A _4.65 ). By applying the computationally derived A _4.65 to the observed aliphatic C–D emission at ∼4.6–4.8 μ m, we find that PAHs with aliphatic C–D units could have tied up a substantial amount of D/H and marginally account for the missing D. The possible routes for generating PAHs with aliphatic C–D units are also discussed.

LaO bands are found in the spectra of cool S-type stars. The bands of the A ^2 Π–X ^2 Σ ^+ transition with $v^{\prime} \leqslant 3$ and v ″ ≤ 4 are rotationally analyzed, providing spectroscopic constants for the A ^2 Π state. Line strengths are calculated using an ab initio transition dipole moment function, and radiative lifetimes for the A ^2 Π state have also been computed. A line list for the A ^2 Π–X ^2 Σ ^+ transition of LaO is provided and can be used to determine LaO stellar abundances.

A spectral investigation of triply ionized gold (Au iv ) has been carried out in the wavelength region of 500–2106 Å. The gold spectra were photographed at the National Institute of Standards and Technology, USA, on a 10.7 m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3 m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Our analysis is theoretically supported by the pseudorelativistic Hartree–Fock (HFR) formalism with a superposition of configuration interactions implemented in Cowan's suite of codes. Radiative transition parameters are also calculated using the HFR+CPOL (core polarization effects) model and the multiconfiguration Dirac–Hartree–Fock approach, and their comparisons are used to evaluate the transition rate data. All the previously reported levels of the 5 d ^8 , 5 d ^7 6 s , and 5 d ^7 6 p configurations are confirmed, except one, and three are newly established. The missing ^1 S _0 level of 5 d ^8 is now established at 55,277.8 cm ^−1 . A total of 981 observed lines (E1 type), classified to 1031 transitions, including 133 newly identified, enabled us to optimize 139 energy levels. Several astrophysically important transitions, forbidden (M1- and E2-type) lines of 5 d ^8 and 5 d ^7 6 s , are provided with their Ritz wavelengths and radiative parameters. A critically evaluated set of energy levels, observed and Ritz wavelengths along with their uncertainties, transition rates, and uniformly scaled intensities of Au iv lines have been presented. Also, large-scale atomic data to compute the opacity of Au iv in the kilonova ejecta have been supplemented in this work.

Line-intensity mapping (LIM) is a promising technique to constrain the global distribution of galaxy properties. To combine LIM experiments probing different tracers with traditional galaxy surveys and fully exploit the scientific potential of these observations, it is necessary to have a physically motivated modeling framework. As part of developing such a framework, in this work, we introduce and model the conditional galaxy property distribution (CGPD), i.e., the distribution of galaxy properties conditioned on the host halo mass and redshift. We consider five galaxy properties, including the galaxy stellar mass, molecular gas mass, galaxy radius, gas-phase metallicity, and star formation rate (SFR), which are important for predicting the emission lines of interest. The CGPD represents the full distribution of galaxies in the five-dimensional property space; many important galaxy distribution functions and scaling relations, such as the stellar mass function and SFR main sequence, can be derived from integrating and projecting it. We utilize two different kinds of cosmological galaxy simulations, a semi-analytic model and the IllustrisTNG hydrodynamic simulation, to characterize the CGPD and explore how well it can be represented using a Gaussian mixture model (GMM). We find that with just a few (approximately three) Gaussian components, a GMM can describe the CGPD of the simulated galaxies to high accuracy for both simulations. The CGPD can be mapped to LIM or other observables by constructing the appropriate relationship between galaxy properties and the relevant observable tracers, which will be discussed in future works.

The hydrogen Balmer decrement (e.g., H α /H β ) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs and changing-look AGNs (CLAGNs), which have steep Balmer decrement but without strong evidence for absorption. We compile a sample of normal AGNs and CLAGNs with a wider distribution of bolometric Eddington ratio ( λ _Edd = L _bol / L _Edd ) and find a strong negative correlation between H α /H β and λ _Edd , which suggests that the Balmer decrement is also accretion-rate dependent. We further explore the Balmer decrement based on the photoionization model using the Cloudy code by considering spectral energy distribution from the accretion disk with different accretion rates (e.g., disk/corona and truncated disk at high and low Eddington ratios, respectively). Both the standard disk and truncated disk predict a negative correlation of H α /H β – λ _Edd , where the relation is steeper in the case of the truncated disk. The negative correlations are also explored in two single CLAGNs. The measured negative correlation of H α /H β – λ _Edd is mainly caused by the lower responsivity $(d\mathrm{log}{L}_{\mathrm{line}}/d\mathrm{log}{L}_{\mathrm{cont}})$ in H α relative to that in H β due to the larger optical depth in the former. We propose that the steep Balmer decrements in low Eddington ratio AGNs (e.g., some Seyferts 1.5–1.9 and CLAGNs) are not simply caused by absorption but mainly caused by the relatively low flux of ionizing photons.

This paper analyzes the emission spectrum of Ar vi and adds new information about this ion. We use a capillary light source to study the Ar vi spectrum, presenting 39 line classifications for the first time, including one line in the ultraviolet region. A total of nine possible Ar vi lines in the ultraviolet between 3288 and 3440 Å are analyzed. We revised the wavelengths of the lines at 1284.01 and 1307.42 Å previously used to identify Ar vi in astronomical objects. The lifetimes, weighted transition rates ( gA ) and their estimated uncertainties, and cancellation factors are obtained using a Hartree–Fock calculation with energy parameters adjusted to fit the values of the experimental levels and modified to include core polarization effects. We analyze all the experimentally known transitions of the Ar vi spectrum, with particular attention to conflicting information. Isoelectronic sequences of energy levels and transitions, for which the trend is not a smooth curve, are analyzed. We revise previous studies where the information needed to support line classifications and level designations is incomplete.

Methanol (CH _3 OH) is an abundant interstellar species and is known to be an important precursor of various interstellar complex organic molecules. Among the methanol isotopologues, CH _2 DOH is one of the most abundant isotopologues and it is often used to study the deuterium fractionation of CH _3 OH in interstellar medium. However, the emission lines of CH _2 DOH can sometimes be optically thick, making the derivation of its abundance unreliable. Therefore, observations of its presumably optically thin ^13 C substituted species, ^13 CH _2 DOH, are essential to overcome this issue. In this study, the rotational transitions of ^13 CH _2 DOH have been measured in the millimeter-wave region from 216 GHz to 264 GHz with an emission-type millimeter- and submillimeter-wave spectrometer by using a deuterium and ^13 C enriched sample. The frequency accuracy of measured ^13 CH _2 DOH is less than a few kHz, and the relative line intensity error is less than 10% in most of the frequency range by taking advantage of the wide simultaneous frequency-coverage of the emission-type spectrometer. These results offer a good opportunity to detect ^13 CH _2 DOH in space, which will allow us to study the deuterium fractionation of CH _3 OH in various sources through accurate determination of the CH _2 DOH abundance.

The first part of this review is a brief reminder of general information concerning atmospheric ozone, particularly related to its formation, destruction, observations of its decrease in the stratosphere, and its increase in the troposphere as a result of anthropogenic actions and solutions. A few words are said about the abandonment of the Airbus project Alliance, which was expected to be the substitute of the supersonic Concorde. This project is over due to the theoretical evaluation of the impact of a fleet in the stratosphere and has been replaced by the A380, which is now operating. The largest part is devoted to calculations and observations of the transitions in the infrared range and their applications for the atmosphere based both on effective models (Hamiltonian, symmetry rules, and dipole moments) and ab initio calculations. The complementarities of the two approaches are clearly demonstrated, particularly for the creation of an exhaustive line list consisting of more than 300,000 lines reaching experimental accuracies (from 0.00004 to 0.001 cm−1) for positions and a sub percent for the intensities in the 10 microns region. This contributes to definitively resolving the issue of the observed discrepancies between line intensity data in different spectral regions: between the infrared and ultraviolet ranges, on the one hand, and between 10 and 5 microns on the other hand. The following section is devoted to the application of recent work to improve the knowledge about the behavior of potential function at high energies. A controversial issue related to the shape of the potential function in the transition state range near the dissociation is discussed.

Two cavity ring‐down spectrometers were employed to accurately measure line intensities in a series of near‐infrared carbon dioxide bands including (30012) ← (00001), (30013) ← (00001), and (30014) ← (00001) near 1.6 μm. Relative combined standard uncertainties for these band intensities were less than 0.1% and showed significant, percent‐level deviations with respect to many existing spectroscopic databases (although close agreement was observed with the HITRAN 2016 database in the (30013) ← (00001) and (30014) ← (00001) bands). Further, the resulting line intensities were utilized in Total Carbon Column Observing Network retrievals and led to significantly reduced biases in the (30012) ← (00001) and (30013) ← (00001) bands. These results indicate that refinements of spectroscopic databases are required to meet the accuracy targets of both ground‐ and satellite‐based remote sensing missions. Key Points: Near‐infrared CO2 line intensities measured with combined standard uncertainties below 0.1%Deviations in excess of 1% were found between these measurements and existing databasesThese new intensities led to reduced biases in atmospheric retrievals of CO2 mixing ratios when using two near‐infrared bands [ABSTRACT FROM AUTHOR]

Due to its major interest for the chemistry of planetary atmospheres and exobiology, accurate spectroscopy data of phosphine are required for the search of signatures of this molecule in astronomical observations. In this work, high resolution infrared laboratory spectra of phosphine were analyzed for the first time in the full Tetradecad region (3769–4763 cm−1) involving 26 rotationally resolved bands. Overall, 3242 lines were assigned in spectra previously recorded by Fourier transform spectroscopy at temperatures 200 K and 296 K, using a combined theoretical model based on ab initio calculations. The total nuclear motion Hamiltonian of PH 3 including ab initio potential energy surface, was reduced to an effective Hamiltonian using the high-order contact transformation method adapted to vibrational polyads of the AB 3 symmetric top molecules, followed by empirical optimization of the parameters. At this step, the experimental line positions were reproduced with a standard deviation of 0.0026 cm−1 that provided unambiguous identification of observed transitions. The effective dipole transition moments of the bands were obtained by fitting to the intensities obtained from variational calculations using the ab initio dipole moment surface. The assigned lines were used to newly determine 1609 experimental vibration-rotational levels up to J max = 18 with energy in the range 3896–6037 cm−1 that represents significant extension towards higher energies compared to previous works. Transitions for all 26 sublevels of the Tetradecad were identified but with noticeably fewer transitions for fourfold excited bands because of their weaker intensity. At the final step, pressure-broadened half widths were attached to each transition and a composite line list adopting ab initio intensities and empirical line positions corrected to the accuracy of about 0.001 cm−1 for strong and medium transitions was validated against experimental spectra available in the literature. [ABSTRACT FROM AUTHOR]

• Determination of the energy difference (ΔE Cis-Trans) between the Cis- and Trans-HONO conformers of nitrous acid. • Relative line intensities for the B-type transitions of pure rotational bands of Trans-HONO and Cis-HONO measured. • Far infrared FTS spectra on SOLEIL. • Line list for HONO in the far infrared region. The first goal of this work is to improve the determination of the energy difference (ΔE Cis-Trans) between the ground vibrational state of the Cis- and Trans-HONO conformers of nitrous acid. For this, high resolution spectra were recorded in the 50–200 cm−1 spectral region at three different temperatures, 240, 270 and 296 K. The relative line intensities for the B-type transitions of pure rotational bands of Trans-HONO and Cis-HONO achieved from our measurements were combined in least squares fit computations to those measured previously by Sironneau et al. [ Sironneau V, Flaud JM, Orphal J, Kleiner I, Chelin P. Absolute line intensities of HONO and DONO in the far-infrared and re-determination of the Energy Difference between the trans- and cis-species of nitrous acid. J Mol Spectrosc 2010;259:100–104 ]. In this way, we can significantly improve the accuracy on the HONO conformer energy difference, with a value for ΔE Cis-Trans = 95.8 ± 9.2 cm−1 compared to SIRΔE Cis-Trans = 99 ± 25 cm−1 in the previous study of Sironneau et al. The second goal is to generate a line list with "absolute" line intensities for the pure rotational bands in the far infrared region of Trans-HONO and Cis-HONO, with both A- and B-type transitions. This new line list proved to be more robust for an improved detection of HONO in astrophysical objects [ Coutens A, Ligterink NFW, Loison JC, Wakelam V, Calcutt H, Drozdovskaya MN, Jørgensen JK, Müller HSP, Van Dishoeck EF, Wampfler SF. The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium. Astronomy & Astrophysics 2019;623:L13 ]. Comparison of the ALMA observations of the HONO transitions towards the protostar IRAS16293 B (black) with the model obtained with the JPL line list for T ex = 300 K and N = 1.4 1015 cm−2 blue dashed line) and the one obtained with our new line list for similar parameters (red solid line). [Display omitted] [ABSTRACT FROM AUTHOR]

• New line list for 2 v 3 (A 1 , E) and v 1 + v 3 (E) states was constructed. • The effective dipole moment was obtained from ab initio intensities. • New spectra at 196 K and 296 were recorded. We report the line list for the 2 v 3 (A 1 , E) and v 1 + v 3 (E) strong bands of the NF 3 molecule which is considered as long living greenhouse gas in the atmosphere with a significant radiative force potential. To construct the line list, the variational calculations based on the ab initio surfaces of the potential energy and dipole moment were combined with high-resolution data on line positions. The effective polyad model was developed for NF 3 by the sixth-order contact transformation of the full rovibrational Hamiltonian. The theoretical parameters of the effective Hamiltonian were then refined by fitting to experimental transitions presented in literature. The parameters of the effective dipole moment were obtained from fitting to our ab initio line intensities. The results of the simulations are consistent with our Fourier Transform spectra within their uncertainty of 10%. [ABSTRACT FROM AUTHOR]

• Analysis of Fourier transform spectra of CH 3 I by multispectrum fitting procedure • Measurements of line positions, intensities and self-broadening coefficients • Empirical, semi-empirical and semi-classical calculations of self-widths • Generation of a complete CH 3 I line list of the ν 6 band for atmospheric databases The present work is dedicated to the ν 6 band of 12CH 3 I with the aim of generating a complete line list for databases. High resolution Fourier transform spectra have been recorded in MONARIS and a multispectrum fitting procedure using Voigt profile has been applied to retrieve line positions, intensities, and self-broadening coefficients for around 1200 transitions of the ν 6 band between 854 and 963 cm−1. Rotational dependences of transition dipole moment squared and self-widths have been studied and empirically modeled. Line positions are retrieved with accuracy equal to 4.10−4 cm−1. The accuracy of line intensities and self-widths measurements is estimated between 5 and 10 %. Theoretical estimates of CH 3 I self-broadening coefficients for large ranges of rotational quantum numbers (0 ≤ J ≤ 70, 0 ≤ K ≤ 20) are also provided in the frame of a semi-classical approach with exact trajectories and of a semi-empirical method including a correction factor to the Anderson-type line-width expression. Comparisons of our results with the data previously published in the literature are presented and discussed. A complete line list of 5787 transitions is generated. Available as supplementary material, this line list can be used for spectroscopic databases and atmospheric or industrial detection of CH 3 I. [ABSTRACT FROM AUTHOR]

• High sensitivity cavity ring down spectroscopy of N 2 O between 5696 and 5910 cm−1. • 3326 lines assigned to 50 bands of five N 2 O isotopologues in natural abundance. • 26 of the 31 bands of the main isotopologue, 14N 2 16O, are newly reported. • The spectroscopic parameters of the upper levels are derived from a band-by-band fit. • Intra- and inter-polyad perturbations identified for a number of bands. In spite of being a greenhouse gas with a large global warming potential, the absorption spectrum of nitrous oxide in the near infrared is insufficiently characterized. In the present work, the spectral region near 1.74 µm (5696–5910 cm−1) is investigated by high sensitivity cavity ring down spectroscopy (CRDS). The noise level of the CRDS spectra corresponds to a typical minimum detectable absorption, α min , below 10-10 cm−1. 3326 transitions are measured and rovibrationally assigned to 50 bands of five nitrous oxide isotopologues (14N 2 16O, 14N15N16O, 15N14N16O, 14N 2 18O and 14N 2 17O) in natural isotopic abundance. The assigned weakest lines have an intensity below 10−28 cm/molecule. For comparison, only three 14N 2 16O bands are included in the HITRAN database in the region, with a 2 × 10−25 cm/molecule intensity cut off. The rovibrational assignments were performed by comparison with predictions performed for each isotopologue in the frame of the effective operator approach. The overall quality of the predictions is satisfactory for line positions. Deviations larger than 0.1 cm−1 are nevertheless noted for 14N 2 16O and 14N 2 18O. The spectroscopic parameters of the upper level of the observed bands were derived from the standard band-by-band fit of the measured line positions. A significant number of bands were found to be perturbed by local rovibrational perturbations and in some cases, extra lines due to an intensity transfer could be assigned. The interaction mechanisms and the perturbers were univocally identified on the basis of the effective Hamiltonian model. In particular, interpolyad couplings were evidenced indicating that the polyad version of the effective Hamiltonian has to be extended to include Coriolis and interpolyad anharmonic interactions. No satisfactory modeling of the N 2 O line intensities is yet available in the region. The CRDS intensity values derived in this work provide a solid set of measurements for future semi-empirical intensity modeling in the region. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlights • New high-resolution infrared spectra of v 2 band have been recorded at the SOLEIL Synchrotron. • 2407 IR data of the v 2 band and 1070 MW data of the GS were assigned. • 71 lines intensities were assigned with a RMS of about 10%. Abstract New experimental high-resolution Fourier-Tansform infrared spectra of the infrared active fundamental ν 2 band of sulfuryl fluoride SO 2 F 2 , have been recorded at a temperature of 193 K and at resolution of 0.00102 cm − 1 at the AILES (Advanced Infrared Line Exploited for Spectroscopy) beamline of the SOLEIL (Source Optimisée de Lumière d'Energie intermédiaire du LURE) Synchrotron facility. A detailed analysis has been performed both in line positions and intensities with the C 2 v TDS (Top Data System) program suite, based on the tensorial formalism developed in Dijon for quasi-spherical top molecules. The effective Hamiltonian was developed up to fourth order. The parameter of the effective dipole moment operator has been determined using the wavefunctions of the effective Hamiltonian operator. 2407 line positions have been measured with global root mean square deviation of about 0.19 × 10 − 3 cm − 1. Using 71 lines intensities, we estimate the uncertainty on calculated line intensities to 10%. To the extent of our knowledge, this is the first time that an absolute intensity analysis has been carried out for sulfuryl fluoride. [ABSTRACT FROM AUTHOR]

Abstract The goal of this study is to measure for the first time absolute line intensities for the ν 6 band of methyl iodide (CH 3 I) centered at 892.918 cm–1. High-resolution Fourier transform spectra were recorded at various pressures for the whole 500–1450 cm–1 spectral range. Using these spectra, a large set of CH 3 I individual line intensities was measured for the ν 6 band. These experimental intensities were least squares fitted to derive the expansion of the ν 6 transition moment operator. The theoretical model used to describe the line positions and intensities accounts for the hyperfine structure in the 61 and ground states and for the vibration-rotation resonances that couple the 61 energy levels with those of the 32 and 21 vibrational states [Perrin et al., J. Mol. Spectrosc. 324 (2016) 28–35]. As the 2ν 3 band is extremely weak, its associated transition moment operator was estimated from band strength available in the literature. A comprehensive list of line positions and intensities was generated for the ν 6 and 2ν 3 bands of CH 3 I at 11 µm, which should be useful for the possible detection of this species by the future IASI-NG satellite instrument (Infrared Atmospheric Sounding Interferometer New Generation), now under preparation (https://iasi-ng.cnes.fr/en/IASI-NG/index.htm). Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

The positions and intensities of 1936 lines observed in the range 7400- of two absorption spectra of ammonia recorded at high resolution using Fourier transform spectroscopy are reported. The accuracy of these line positions is estimated to range from 0.001 to from the lower to the upper limits of the spectral range considered, while the accuracy of the line intensities is estimated to be around 10% or better. Also reported are less-accurately measured positions and intensities of 1985 lines retrieved from these two spectra or from only one of them. These results are compared with the data measured recently in a spectrum recorded in 1980 at the Kitt Peak National Solar Observatory [Barton et al., J. Mol. Spectrosc. 325, 7 (2016)] and provided in HITRAN 2016, as well as line positions and intensities measured in this work in the same Kitt Peak spectrum. [ABSTRACT FROM AUTHOR]

The positions and intensities of 1936 lines observed in the range 7400- of two absorption spectra of ammonia recorded at high resolution using Fourier transform spectroscopy are reported. The accuracy of these line positions is estimated to range from 0.001 to from the lower to the upper limits of the spectral range considered, while the accuracy of the line intensities is estimated to be around 10% or better. Also reported are less-accurately measured positions and intensities of 1985 lines retrieved from these two spectra or from only one of them. These results are compared with the data measured recently in a spectrum recorded in 1980 at the Kitt Peak National Solar Observatory [Barton et al., J. Mol. Spectrosc. 325, 7 (2016)] and provided in HITRAN 2016, as well as line positions and intensities measured in this work in the same Kitt Peak spectrum. [ABSTRACT FROM AUTHOR]

Monitoring ozone concentrations in the Earth’s atmosphere using spectroscopic methods is a major activity which undertaken both from the ground and from space. However there are long-running issues of consistency between measurements made at infrared (IR) and ultraviolet (UV) wavelengths. In addition, key O 3 IR bands at 10 µm, 5 µm and 3 µm also yield results which differ by a few percent when used for retrievals. These problems stem from the underlying laboratory measurements of the line intensities. Here we use quantum chemical techniques, first principles electronic structure and variational nuclear-motion calculations, to address this problem. A new high-accuracy ab initio dipole moment surface (DMS) is computed. Several spectroscopically-determined potential energy surfaces (PESs) are constructed by fitting to empirical energy levels in the region below 7000 cm − 1 starting from an ab initio PES. Nuclear motion calculations using these new surfaces allow the unambiguous determination of the intensities of 10 µm band transitions, and the computation of the intensities of 10 µm and 5 µm bands within their experimental error. A decrease in intensities within the 3 µm is predicted which appears consistent with atmospheric retrievals. The PES and DMS form a suitable starting point both for the computation of comprehensive ozone line lists and for future calculations of electronic transition intensities. [ABSTRACT FROM AUTHOR]

Thirty well isolated ro-vibrational transitions of the 30011e – 00001e band of 12 C 16 O 2 at 1.54 μm have been recorded with a laser-locked cavity ring-down spectrometer. The line intensities were obtained with accuracies better than 0.85%. Comparisons of the line intensities determined in this work with literature experimental values and those from HITRAN2016, AMES, UCL-IAO and CDSD-296 line lists are given. [ABSTRACT FROM AUTHOR]

The germane molecule, GeH 4 , is present in the atmospheres of giant planets Jupiter and Saturn. The ongoing NASA mission Juno has renewed interest in its spectroscopy, whose accurate modeling is essential for the retrieval of other tropospheric species. We present here the first complete analysis and modeling of line positions and intensities in the strongly absorbing ν 1 / ν 3 stretching dyad region near 2100 cm − 1 , for all five germane isotopologues in natural abundance. New infrared spectra were recorded, absolute intensities were extracted through a careful procedure and modeled thanks to the formalism and programs developed in the Dijon group. A database of calculated germane lines, GeCaSDa, has been build and is available online through the Virtual Atomic and Molecular Data Centre (VAMDC) portal and at http://vamdc.icb.cnrs.fr/PHP/gecasda.php . [ABSTRACT FROM AUTHOR]

Improved analysis of positions and intensities of phosphine spectral lines in the Octad region 2733–3660 cm −1 is reported. Some 5768 positions and 1752 intensities were modelled with RMS deviations of 0.00185 cm −1 and 10.9%, respectively. Based on an ab initio potential energy surface, the full Hamiltonian of phosphine nuclear motion was reduced to an effective Hamiltonian using high-order Contact Transformations method adapted to polyads of symmetric top AB 3 -type molecules with a subsequent empirical optimization of parameters. More than 2000 new ro-vibrational lines were assigned that include transitions for all 13 vibrational Octad sublevels. This new fitting of measured positions and intensities considerably improved the accuracy of line parameters in the calculated database. A comparison of our results with experimental spectra of PNNL showed that the new set of line parameters from this work permits better simulation of observed cross-sections than the HITRAN2012 linelist. In the 2733–3660 cm −1 range, our integrated intensities show a good consistency with recent ab initio variational calculations. [ABSTRACT FROM AUTHOR]

The absorption spectra of carbon dioxide have been recorded in the near infrared region from 10,000 to 10,300 cm -1 , using the Bruker IFS 125 HR Fourier transform spectrometer and a 30 m multipass cell with the White type optical system. The spectra were recorded at a spectral resolution of 0.03 cm − 1 , room temperature, a path length of 953.6 m and at two pressures of 294 and 523 mbar. The achieved sensitivity (noise equivalent absorption) at the level of k ν =1.38×10 − 10 cm −1 allowed detection of a number of new transitions with the intensity values down to 10 –29 cm/molecule at 296 K. Two bands 60014-00001 and 60015-00001 of 12 C 16 O 2 were detected for the first time. The line positions and intensities of these bands were determined using the Voigt profile as a line shape. The uncertainty of the line position determination was estimated to be about 0.003 cm -1 for the unblended lines with a high value of the signal-to-noise ratio. The uncertainty of the line intensity determination varies from 4% to 40% depending on the strength of the line and the extent of the line overlapping. The measured line intensities of the 60014-00001 and 60015-00001 bands together with those published earlier for the Δ P =15 series of transitions were used to fit the effective dipole moment parameters of this series. Here P =2 V 1 + V 2 +3 V 3 is the polyad number ( V i ( i =1,2,3) are the harmonic oscillators quantum numbers). The fitted parameters reproduce the measured line intensities within their experimental uncertainties. Using the effective Hamiltonian parameters published earlier and the fitted effective dipole moment parameters the line positions and intensities of the 6001 i -00001 ( i =1,2,3,4,5,6,7) bands have been calculated. A comparison of the measured line positions and intensities to those contained in the new version ( huang.seti.org ) AMES line list as well as in the High-T line list are given. [ABSTRACT FROM AUTHOR]

The lack of spectroscopic measurements for rare CO 2 isotopologues was the main motivation of this work. In our present study we report line intensity measurements for 16 O 12 C 17 O made with a high resolution Fourier transform spectrometer (Bruker IFS-125HR) and a 21 m path cryogenic Herriott cell at Jet Propulsion Laboratory. For this, a 17 O-enriched CO 2 gas sample was used, which comes as a mixture of primary and several minor CO 2 isotopologues. The mole fraction of the 16 O 12 C 17 O isotopologue in the mixture was determined to be 0.3991 by mass spectrometry from a Stable Isotope Ratio Mass Spectrometer (SIRMS) under stochastic distribution assumption at thermal equilibrium. Since the collisional narrowing effect was observed, the Rautian molecular line shape profile was systematically adopted instead of the Voigt profile. Absolute line positions were also investigated by performing a wavenumber calibration based on CO, HCl and a few well-known 16 O 12 C 16 O transitions. Finally, around 1000 transitions were studied between 4604 and 5126 cm −1 involving 15 bands of the 16 O 12 C 17 O isotopologue. All the measured line intensities were renormalized to be the values for 100% pure isotopologue sample. Transition dipole moments and Herman-Wallis factors were derived enabling a global comparison with theoretical calculations and predictions for the 15 bands of the 16 O 12 C 17 O isotopologue. For the measured line positions, the absolute accuracy is around 2×10 −4 cm −1 . The accuracies of retrieved line intensities are 2 – 5% for five cold and two hot bands, and 6–30% for eight other weaker hot bands. Results from this work were in a good agreement with HITRAN 2012 for positions, but showed rather significant discrepancies for line intensities. An extensive line list was generated from new experimental measurements in order to improve and validate spectroscopic knowledge of 12 C 16 O 17 O isotopologue in support of atmospheric remote sensing for the Earth (e.g., OCO-2 mission), Mars and Venus. [ABSTRACT FROM AUTHOR]

• Ab initio PECs, TDMs and partition functions of AlO are calculated. • Comparisons of radiative lifetimes and line intensities of AlO are given. • Temperature-dependent spectroscopy below 55,000 cm−1 is presented. • The electronic transitions from X2Σ+ to A2Π, B2Σ+, C2Π and D2Σ+ are important. The spectrum of AlO is widely used in various applications including the explorations of interstellar space, studies of laser ablation, combustions of Al-containing fuels and so on. In this work, we reported the spectroscopy of the AlO radical at temperatures of 300 ∼ 15,000 K for the wavenumber range of 1 ∼ 55,000 cm−1. Firstly, we extended our previous calculations of the potential energy curves (PECs) and transition dipole moments (TDMs) for AlO (Bai, Qin & Liu, MNRAS, 2022, 510:1649–1656) to higher B2Σ+, D2Σ+, 1′2Π and 1′'2Π electronic states, with the consideration of Davidson correction, scalar relativistic correction and core-valence correlation. Partition functions, Einstein coefficients and radiative lifetimes of AlO were then obtained by solving the nuclear-motion Schrödinger equation. The partition functions reveal that the AlO molecules mainly exist in the X2Σ+ state at temperatures of 10 ∼ 6270 K and in the A2Π state at temperatures of 6270 ∼ 15,000 K in the thermodynamic equilibrium. Finally, line intensities and spectra for different electronic transitions of AlO were calculated. The results show that the X2Σ+ → C2Π and X2Σ+ → D2Σ+ transitions dominate in the ultraviolet waveband. Comparisons of the TDMs, radiative lifetimes, line intensities and spectra with previous theoretical and experimental values indicate that our calculated data in the ultraviolet waveband are reliable and may be used for the radiation field calculation. [Display omitted] [ABSTRACT FROM AUTHOR]

• High sensitivity cavity ring down spectroscopy of nitrous oxide between 7250 and 7653 cm−1. • Line intensity information is obtained for about 4200 transitions. • Eight new bands are reported. • A few local resonance interactions are identified and some extra lines are assigned. • Validation tests of the NOSL-296 and Ames-296 line lists. We revisit the weak absorption spectrum of natural nitrous oxide between 7250 and 7653 cm−1 for which rovibrational assignments were previously reported in Lu et al. (doi:10.1016/j.jqsrt.2012.03.005). Our main goal is to provide intensity information for the high number of lines detected by cavity ring down spectroscopy in the region. Line parameters of about 4180 transitions were retrieved from a line-by-line profile adjustment. They belong to 69 bands of the 14N 2 16O, 14N15N16O, 15N14N16O, and 14N 2 18O isotopologues, present in natural isotopic abundance in the sample. Eight bands are newly reported. The band-by-band analysis allowed for the determination of refined values of the rovibrational parameters of a total of 68 upper vibrational states. Eight 14N 2 16O bands were found to be affected by local rovibrational perturbations and a total of 31 extra lines due to an intensity transfer could be identified. The comparison with the recent NOSL-296 and Ames line lists is discussed in detail. The overall agreement is very satisfactory. As concerns line intensities, the NOSL and Ames lists show both specific advantages and drawbacks which are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

• CW-ECDL laser based high-resolution TDLAS spectroscopy of acetylene in 6474–6515 cm−1 spectral region. • First experimental measurement of self-broadening coefficients of approximately 27 l -doublets spectral lines in the p branch of the ν 1 + ν 3 + ν 4 ‒ ν 4 band. • Measurement of line intensities of P -branch transitions of ν 1 + ν 3 + ν 4 ‒ ν 4 band. • Rotational dependency of the self-broadening coefficients have been studied and modelled with third order polynomial. • l -type doubling constants of ν 1 + ν 3 + ν 4 and ν 4 states were determined. Acetylene is considered to be an important molecule for spectroscopic research due to its role in environmental chemistry, astrophysics, biochemistry and photochemistry of various planets. The high resolution spectroscopic studies of acetylene (12C 2 H 2) in the 6474–6515 cm−1 spectral range have been performed using in-house developed external-cavity diode laser absorption spectroscopy technique. The study is focused on experimental measurement of self-broadening coefficients (γ self) and line intensities of 27 l- doublet ro-vibrational lines belonging to the P -branch transition of ν 1 + ν 3 + ν 4 ‒ ν 4 hot band lying in the 6474–6515 cm−1 spectral range. The γ self and line intensity have been retrieved by modelling of each experimentally observed rotational line with standard Voigt line profile using custom written python based computer program. The measured γ self and line intensities were compared with the values present in HITRAN2020 database, showing mean difference of about -1.9% and 2.48%, respectively. In contrast to the line intensity, where rotational and symmetry dependency are readily visible, γ self exhibits only rotational dependency. The l -type doubling constants of both ν 1 + ν 3 + ν 4 and ν 4 states of ν 1 + ν 3 + ν 4 ‒ ν 4 hot band have also been obtained. Detailed understanding of these molecular parameters will play an important role in modelling of planetary atmospheres. [Display omitted] [ABSTRACT FROM AUTHOR]

Highly correlated ab initio calculations were performed for accurate determination of γ (A² Σ+-X² П) and β (B2 П-X² П) band systems of NO molecule. Highly accurate multi-reference configuration inter-action approach was used to investigate the potential energy curves (PECs) and transition dipole moment curves. We correctly and fully described their diffuse wave functions by the obvious balance between the valence and Rydberg character of the X² П,A² Σ+, B2 П, C² П and D² Σ+ states. The PECs of the three states (X²П, A² Σ+ and B² П) by using the aug-cc-pV5Z (aV5Z) basis set for N and O atoms agreed well with the Rydberg--Klein--Rees potential. Moreover, the Einstein A coefficients were calculated to predict the lifetimes, where the vibrational bands included v' = 0-8, v" = 0-29 for γ system and v' = 0-11, v" = 0-31 for β system. The spectral line intensities of the γ and β systems for atmosphere and high temperature were provided. [ABSTRACT FROM AUTHOR]

A recent paper [1] presents a high-resolution, high-temperature version of the Nitrogen Dioxide Spectroscopic Databank called NDSD-1000. The NDSD-1000 database contains line parameters (positions, intensities, self- and air-broadening coefficients, exponents of the temperature dependence of self- and air-broadening coefficients) for numerous cold and hot bands of the 14 N 16 O 2 isotopomer of nitrogen dioxide. The parameters used for the line positions and intensities calculation were generated through a global modeling of experimental data collected in the literature within the framework of the method of effective operators. However, the form of the effective dipole moment operator used to compute the NO 2 line intensities in the NDSD-1000 database differs from the classical one used for line intensities calculation in the NO 2 infrared literature [12]. Using Fourier transform spectra recorded at high resolution in the 6.3 µm region, it is shown here, that the NDSD-1000 formulation is incorrect since the computed intensities do not account properly for the (Int(+)/Int(−)) intensity ratio between the (+) (J = N+ 1/2) and (−) (J = N−1/2) electron – spin rotation subcomponents of the computed vibration rotation transitions. On the other hand, in the HITRAN or GEISA spectroscopic databases, the NO 2 line intensities were computed using the classical theoretical approach, and it is shown here that these data lead to a significant better agreement between the observed and calculated spectra. [ABSTRACT FROM AUTHOR]

In this work, we report first-principle theoretical predictions of methane spectral line intensities that are competitive with (and complementary to) the best laboratory measurements. A detailed comparison with the most accurate data shows that discrepancies in integrated polyad intensities are in the range of 0.4%–2.3%. This corresponds to estimations of the best available accuracy in laboratory Fourier Transform spectra measurements for this quantity. For relatively isolated strong lines the individual intensity deviations are in the same range. A comparison with the most precise laser measurements of the multiplet intensities in the 2ν 3 band gives an agreement within the experimental error margins (about 1%). This is achieved for the first time for five-atomic molecules. In the Supplementary Material we provide the lists of theoretical intensities at 269 K for over 5000 strongest transitions in the range below 6166 cm −1 . The advantage of the described method is that this offers a possibility to generate fully assigned exhaustive line lists at various temperature conditions. Extensive calculations up to 12,000 cm −1 including high-T predictions will be made freely available through the TheoReTS information system (http://theorets.univ-reims.fr, http://theorets.tsu.ru) that contains ab initio born line lists and provides a user-friendly graphical interface for a fast simulation of the absorption cross-sections and radiance. [ABSTRACT FROM AUTHOR]

Parameters of high-temperature water vapor spectral lines presented in the well-known spectroscopic databases are discussed. As a reliability criterion for parameter values, recent experimental data on the transmittance measured with spectral resolution of 1 cm at Т ~ 1000 K are employed. As a result of our analysis, 156 spectral lines were revealed (12 of them were found previously) in the HITEMP2010 database the use of which in calculations of the transmittance leads to considerable deviations (≥20%) from the available experimental data. The line intensities determined by this method exceed by 3 times and more the data presented in other spectroscopic bases. Additionally, the line intensities from the HITEMP2010 database in the spectral range 10-6000 cm are completely compared with the result of semiempirical calculation at the high temperature available from the literature. The hot bands for which the relative deviation of the integral intensities exceeds 10% at T = 1302 K are identified. It is established that as a whole, the most reliable integral hot band intensities are contained in the HITEMP2010 database. This is confirmed by their least deviations from the measured transmittance at high temperatures. As a result, it is demonstrated that to obtain the best coincidence (Δ = 2.64%) with the measured data in the range 1000-2000 cm in calculation based on the HITEMP2010 database, the parameter values recommended in the present work for lines with overestimated intensities and different distribution of the temperature coefficients must be used. [ABSTRACT FROM AUTHOR]

This contribution is the second part of the analysis of the room temperature absorption spectrum of 18 O enriched carbon dioxide by very high sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm -1 (1.43–1.26 μm). Overall, more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues were rovibrationnally assigned. In a first part (Kassi et al. J Quant Spectrosc Radiat Transfer 187 (2017) 414–425, http://dx.doi.org/10.1016/j.jqsrt.2016.09.002 ), the results relative to mono-substituted isotopologues, 16 O 12 C 18 O, 16 O 12 C 17 O, 12 C 16 O 2 and 13 C 16 O 2 , were presented. This second contribution is devoted to the multiply-substituted isotopologues or clumped isotopologues of particular importance in geochemistry: 16 O 13 C 18 O, 16 O 13 C 17 O, 12 C 18 O 2 , 17 O 12 C 18 O, 12 C 17 O 2 , 13 C 18 O 2 and 17 O 13 C 18 O. On the basis of the predictions of effective Hamiltonian models, a total of 3195 transitions belonging to 73 bands were rovibrationnally assigned for these seven species. Among the 73 observed bands, 55 are newly reported. All the identified bands correspond to Δ P= 10 and 11 series of transitions, where P= 2V 1 +V 2 +3V 3 is the polyad number ( V i are vibrational quantum numbers). The accurate spectroscopic parameters of 70 bands have been determined from the standard band-by-band analysis. Global fits of the measured line intensities of the Δ P= 10 series of transitions of 17 O 12 C 18 O and 16 O 13 C 18 O and of the Δ P= 11 series of transitions of 12 C 18 O 2 , 17 O 12 C 18 O, 16 O 13 C 18 O and 13 C 18 O 2 were performed to determine the corresponding sets of the effective dipole moment parameters. [ABSTRACT FROM AUTHOR]