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A discharge‐flow modulated molecular beam mass spectrometry technique has been used to determine the rate constant for the reaction of ground state oxygen atoms with C2H4S in the temperature range 220–950 K. The reaction rate constant has been determined directly by monitoring C2H4S in an excess of O atoms and through competitive reaction of oxygen atoms with C2H4S and Br2. Weak, negative temperature dependence is observed below 300 K, whereas positive temperature dependence is observed above 380 K: k = 1.13 × 10–12 (T/298)2.18 exp(733/T) cm3 molecule–1 s–1. We estimate this expression to be accurate within 15% over the investigated temperature range. SO and C2H4 have been detected as reaction products and a branching ratio of unity (with uncertainty of 10%) has been found for the channel forming these two species in the temperature range 300–900 K, confirming that the title reaction is an efficient source of SO radicals. [ABSTRACT FROM AUTHOR]

N-polar AlN epilayers were grown on the N-face of single-crystal bulk AlN substrates by plasma-assisted molecular beam epitaxy. A combination of in situ thermal deoxidation and Al-assisted thermal desorption at high temperature aided in removing native surface oxides and impurities from the N-polar surface of the substrate enabling successful homoepitaxy. Subsequent epitaxial growth of the AlN layer on the in situ cleaned substrates, grown in a sufficiently high Al droplet regime, exhibited smooth surface morphologies with clean and wide atomic steps. KOH etch studies confirmed the N-polarity of the homoepitaxial films. Secondary ion mass spectrometry profiles show Si and H impurity concentrations below the noise levels, whereas O and C impurity concentrations of ∼ 8 × 1 0 17 and ∼ 2 × 1 0 17 atoms/cm3 are observed, respectively. Although the structural defect densities are low, they interestingly appear as inversion domains of different dimensionalities. [ABSTRACT FROM AUTHOR]

Here, we report on a new approach based on laser driven molecular beams that provides simultaneously nanoscale liquid droplets and gas-phase sample delivery for femtosecond electron diffraction studies. The method relies on Picosecond InfraRed Laser (PIRL) excitation of vibrational modes to strongly drive phase transitions under energy confinement by a mechanism referred to as Desorption by Impulsive Vibrational Excitation (DIVE). This approach is demonstrated using glycerol as the medium with selective excitation of the OH stretch region for energy deposition. The resulting plume was imaged with both an ultrafast electron gun and a pulsed bright-field optical microscope to characterize the sample source simultaneously under the same conditions with time synchronization equivalent to sub-micrometer spatial resolution in imaging the plume dynamics. The ablation front gives the expected isolated gas phase, whereas the trailing edge of the plume is found to consist of nanoscale liquid droplets to thin films depending on the excitation conditions. Thus, it is possible by adjusting the timing to go continuously from probing gas phase to solution phase dynamics in a single experiment with 100% hit rates and very low sample consumption (<100 nl per diffraction image). This approach will be particularly interesting for biomolecules that are susceptible to denaturation in turbulent flow, whereas PIRL–DIVE has been shown to inject molecules as large as proteins into the gas phase fully intact. This method opens the door as a general approach to atomically resolving solution phase chemistry as well as conformational dynamics of large molecular systems and allow separation of the solvent coordinate on the dynamics of interest. [ABSTRACT FROM AUTHOR]

The temperature-dependent desorption behavior of selenium and tellurium is investigated using a heated quartz crystal microbalance. Prior to heating the quartz crystal microbalance, selenium and tellurium films with varying thickness were deposited using thermal effusion cells in a molecular beam epitaxy system for subsequent determination of temperature-dependent mass loss of the deposited films. The desorption rate for tellurium was found to exhibit one sharp peak around 190 °C, indicating the loss of the entire film irrespective of film thickness within a temperature window of 20 °C, which was completely evaporated at 200 °C. Similar experiments for selenium revealed that the thermal desorption took place via a two-stage process with a smaller portion of the material desorbing within an even narrower temperature window of 5 °C at a much lower peak temperature of 65 °C, while most selenium desorbed within a temperature range of 10 °C around 90 °C. This two-stage behavior indicated the presence of at least two chemically distinct selenium species or binding states. The direct and quantitative determination of the chalcogen desorption process provides important insights into the kinetics of chalcogenide-based film growth and is in addition of applied benefit to the research community in the area of Se/Te capping and decapping of air sensitive materials as it provides temperature ranges and rates at which full desorption is achieved. Our work furthermore points toward the need for a more detailed understanding of the chemical composition state of atomic and molecular beams supplied from thermal evaporation sources during growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • We demonstrated the buffer-gas cooling production of the lead monofluoride (PbF) beam and observed the B (υ' = 0) ← X 1 (υ = 0) transition. • We identified 171 hyperfine-structure-resolved transitions for three PbF isotopologues and reported hyperfine constants owing to both 207Pb and 19F nuclei. • The buffer-gas-cooled PbF beam and its spectroscopic characterization will be essential in developing sensitive detection schemes for measuring the electron Electric Dipole Moment (e EDM). Establishing a nonzero measurement of the electron Electric Dipole Moment (e EDM) has long been a fundamental pursuit in atomic, molecular and optical physics, offering possible insights into new physics beyond the Standard Model. In this regard, lead monofluoride (PbF) has emerged as a potential candidate for measuring e EDM primarily due to its suitable properties such as the strong internal effective electric field, and e EDM-sensitive ground state with large Ω-doubling and small magnetic g factor. In the present work, we realized the production of a buffer-gas-cooled PbF molecular beam and characterized its high-resolution spectroscopy in the B 2Σ+(υ' =0) ← X 1 2Π 1/2 (υ = 0) transition, including both direct absorption and laser-induced fluorescence spectroscopy. A highly concentrated beam of PbF molecules is obtained with a central forward velocity of 223 ± 17 m/s, while 81, 66 and 24 hyperfine-structure-resolved spectral lines with a frequency accuracy of 40 MHz have been assigned respectively for 208PbF, 207PbF and 206PbF isotopologues. The hyperfine constants due to the 19F nucleus (A ∥ and A ⊥) of the B state are reported for the first time, and those of the 207Pb nucleus have been also updated. Such a cryogenic molecular beam of PbF in association with its hyperfine-structure-resolved spectral atlas of the B 2Σ+(υ' =0) ← X 1 2Π 1/2 (υ = 0) transition will be essential in developing sensitive detection schemes towards the e EDM measurement. [ABSTRACT FROM AUTHOR]

We developed triple nozzle evaporator that can make collimated organic molecular beam. We can reduce inner pressure below final nozzle 1/150 times lower than general evaporator by using triple nozzle structure and recycling path. As a results, the angular flux distribution of triple nozzle evaporator is similar with the cosine to the 100 th graph. And 80% of total flux are concentrated within only ±8° angle region. We expect that it will be helpful to achieve ultra‐high resolution in AMOLED AR/VR and increase material utilization in AMOLED mass production. [ABSTRACT FROM AUTHOR]

Microsolvated bimolecular nucleophilic substitution (SN2) reaction of monohydrated hydrogen peroxide anion [HOO(O)] with methyl chloride (CCl) has been investigated with direct chemical dynamics simulations at the M06-2X/6-31+G(d,p) level of theory. Dynamic exit-channel pathways and corresponding reaction mechanisms at the atomic level are revealed in detail. Accordingly, a product distribution of 0.85:0.15 is obtained for Cl:Cl(O), which is consistent with a previous experiment [D. L. Thomsen et al. J. Am. Chem. Soc. 135, 15508 (2013)]. Compared with the HOO + CCl SN2 reaction, indirect dynamic reaction mechanisms are enhanced by microsolvation for the HOO(O) + CCl SN2 reaction. On the basis of our simulations, further crossed molecular beam imaging experiments are highly suggested for the SN2 reactions of HOO + CCl and HOO(O) + CCl. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

We observed hyperfine-resolved high-resolution fluorescence excitation spectra of k = 0, N = 1 ← 0 transitions in 82 vibronic bands of the òB2 ← X²A1 system of 14NO2 in the 14 500-16 800 cm-1 region by crossing a jet-cooled molecular beam and a single-mode dye laser beam at right angles. We determined hyperfine interaction constants of the lower and upper states for all the observed vibronic bands based on the analysis of the hyperfine structures of k = 0, N = 1 ← 0 transitions. Most of the determined Fermi contact interaction constants were found to be distributed in 0.0013-0.0038 cm-1, which are intermediate in magnitude between those in lower and higher energy region reported by other groups. A sharp decreasing of the Fermi contact interaction constant was found in 16 200-16 600 cm-1, and it may be caused by the interaction with the dark C²A2 state. The hyperfine interaction constants are powerful clues to obtain reliable vibronic assignment. We tentatively assigned vibronic bands located at 14 836 cm-1, 15 586 cm-1, and 16 322 cm-1 as the transitions to the intrinsic (0,7,0), (0,8,0), and (0,9,0) vibrational levels of the òB2 state, respectively. [ABSTRACT FROM AUTHOR]

The design and characterization of a new laser-desorption molecular beam source, tailored for use in x-ray free-electron laser and ultrashort-pulse laser imaging experiments, is presented. It consists of a single mechanical unit containing all source components, including the molecular-beam valve, the sample, and the fiber-coupled desorption laser, which is movable in five axes, as required for experiments at central facilities. Utilizing strong-field ionization, we characterize the produced molecular beam and evaluate the influence of desorption laser pulse energy, relative timing of valve opening and desorption laser, sample bar height, and which part of the molecular packet is probed on the sample properties. Strong-field ionization acts as a universal probe and allows detecting all species present in the molecular beam, and hence enables us to analyze the purity of the produced molecular beam, including molecular fragments. We present optimized experimental parameters for the production of the purest molecular beam, containing the highest yield of intact parent ions, which we find to be very sensitive to the placement of the desorbed-molecule plumes within the supersonic expansion. [ABSTRACT FROM AUTHOR]

We studied spin dephasing processes in GaAs/AlGaAs multiple quantum wells (MQWs) grown on a semi-insulating (110)-oriented GaAs substrate using the time-resolved Kerr rotation (TRKR) technique. The TRKR spectra gives the electron g-factor in MQWs, as well as the spin dephasing time (SDT) for electron spins within the sample plane. The electron g-factor shows a strong two-fold anisotropy, while the in-plane SDT remains almost isotropic. The anisotropy of the electron g-factor increases monotonically with the spread of more electron wave functions into the AlGaAs barrier. The two-fold symmetry of the electron g-factor is discussed with a phenomenological model based on spin splitting of energy bands caused by spin-orbit coupling. [ABSTRACT FROM AUTHOR]

Three alkali metal hydrogen phthalate salts (denoted as XAP, X = K+, Rb+, and Cs+) are chosen as substrates for the growth of quaterthiophene (4T) and hexathiophene (6T) thin films by organic molecular beam epitaxy to study the influence of gradual changes of surface unit cell parameters on the epitaxial growth. The increment of substrate lattice parameters increases the distance between the planes that define the furrows where oligothiophene molecules lie, while keeping unmodified the interactions between the overlayer and the substrate. Atom-atom potential simulations predict the preferential azimuthal orientations of the overlayer, which are compared with those experimentally observed. The agreement between simulations and experiments about contact planes and orientation of the crystalline domains in the films is satisfactory for both 4T/XAP and 6T/XAP. The increasing width of the surface furrows existing on moving from KAP to RbAP and CsAP does not cause any significant variation of the orientation and density of the overlayer domains, demonstrating that the interaction between overlayer and substrate is the key factor guiding organic epitaxial growth. [ABSTRACT FROM AUTHOR]

• Sb 2 Se 3 solar cells obtained by the chemical molecular beam deposition method. • Increase of conductivity on Sb 2 Se 3 thin films at higher substrate temperatures (T s). • Substrate temperature affects the Sb 2 Se 3 film structure and solar cells' performance. • Dependence of trap state density on t s of Sb 2 Se 3 thin film. Antimony triselenide (Sb 2 Se 3) stands as a promising candidate for photovoltaic (PV) applications due to its favorable material- and optoelectronic properties. However, the realization of further advancements in device efficiency is hindered by the substantial deficit in open-circuit voltage (V OC) attributed to the presence of multiple defect states and detrimental recombination losses. In this work, solar cells based on Sb 2 Se 3 absorber layers deposited by chemical-molecular beam deposition method at substrate temperatures of 400 °C, 450 °C, and 500 °C. Due to the precise control of the Sb/Se ratio, Sb 2 Se 3 thin films with stoichiometric composition were obtained, which was confirmed by energy-dispersive X-ray spectroscopy. The effect of substrate temperature on the morphology and electrical properties of Sb 2 Se 3 thin-films were characterized by scanning electron microscopy and hot probe method. The PV performance of Mo/Sb 2 Se 3 /ZnCdS/CdS/ZnO/ITO/Au devices were investigated by current-voltage characteristics, and external quantum efficiency. The conductivity values tend to increase from 1.2 × 10–6 to 4.6 × 10–4 (Ω cm)-1 as the substrate temperature increased. Whereas, the trap-state density was determined between 7.3 × 1013 – 1.7 × 1014 cm-3 in the absorber layer by the space charge limited current method. Ultimatety, it has been shown that defect densities in Sb 2 Se 3 films can be suppressed to some extent by optimizing the substrate temperature. Best solar cell performance of 5.36%, resulting from V OC of 476 mV, short-circuit current densit of 22.97 mA/cm−2, and fill factor of 49% at the substrate temperature of 450 °C. [ABSTRACT FROM AUTHOR]

The radioactive nuclide 225Ac is one of the few promising candidates for cancer treatment by targeted-α\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\alpha$$\end{document}-therapy, but worldwide production of 225Ac faces significant limitations. In this work, the Isotope Separation On-Line method was used to produce actinium by irradiating targets made of uranium carbide and thorium carbide with 1.4-GeV protons. Actinium fluoride molecules were formed, ionized through electron impact, then extracted and mass-separated as a beam of molecular ions. The composition of the mass-selected ion beam was verified using time-of-flight mass spectrometry, α\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\alpha$$\end{document}- and γ\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\gamma$$\end{document}-ray decay spectrometry. Extracted quantities of 225Ac19F2+\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$^{225}\textrm{Ac}^{19}\textrm{F}_2^{+}$$\end{document} particles per μ\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\upmu$$\end{document}C of incident protons were 3.9(3)×107\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$3.9(3)\times 10^7$$\end{document} from a uranium carbide target and 4.3(4)×107\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$4.3(4)\times 10^7$$\end{document} for a thorium carbide target. Using a magnetic mass separator, the long-lived contamination 227 Ac is suppressed to <5.47×10-7\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$<5.47\times 10^{-7}$$\end{document} (95% confidence interval) with respect to 225Ac by activity. Measured rates scale to collections of 108 kBqμ\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\upmu$$\end{document}A-1\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$^{-1}$$\end{document}h-1\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$^{-1}$$\end{document} of directly produced 225Ac19F2+\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$^{225}\textrm{Ac}^{19}\textrm{F}_2^{+}$$\end{document}. [ABSTRACT FROM AUTHOR]

• Deposition technology for antimony sulfide selenide (Sb 2 (S x Se 1-x) 3) thin films. • Sb 2 (S x Se 1-x) 3 thin films obtained by the chemical molecular beam deposition method. • Band gap of Sb 2 (S x Se 1-x) 3 was 1.2–1.36 eV by varying S/(S +Se) ratio from 0.03 to 0.08. • Changing the ratio shifts peaks toward a higher 2θ angle (+0.15°). Antimony sulfide selenide, Sb 2 (S x Se 1-x) 3 (x = 0–1), is a tunable bandgap compound that combines the advantages of antimony sulfide (Sb 2 S 3) and antimony selenide (Sb 2 Se 3). This material shows great potential as a light-absorbing material for low-cost, low-toxicity, and highly stable thin-film solar cells. In this study, Sb 2 (S x Se 1-x) 3 thin films were deposited by chemical-molecular beam deposition on soda-lime glass substrates using antimony (Sb), selenium (Se), and sulfur (S) precursors at a substrate temperature of 420 °C. By independently controlling the source temperatures of Sb, Se, and S, Sb 2 (S x Se 1-x) 3 thin films with varying component ratios were obtained. Scanning electron microscopy revealed significant changes in the surface morphology of the films depending on the elemental ratio of [S]/([S]+[Se]). Crystallites shaped like cylindrical microrods with d = 0.5–2 µm diameter and l = 3–5 µm length were grown at a certain angle on the substrate. X-ray diffraction patterns showed peaks corresponding to the orthorhombic structures of Sb 2 Se 3 , Sb 2 S 3 and their ternary compounds Sb 2 (S x Se 1-x) 3. The optical characterization revealed a high absorption coefficient of 105 cm−1 in the visible and near-infrared light regions. The band gap of the compounds changed almost linearly from 1.2 eV to 1.36 eV with a change in the ratio of elements [S]/([S]+[Se]) from 0.03 to 0.08. [ABSTRACT FROM AUTHOR]

• Ln-mediated dehydrogenation of ethylamine where Ln = La and Ce. • Vibrationally resolved ionization spectra and precise adiabatic ionization energies of Ln(NCH 2 CH 3). • Spin-orbit coupling of Ce(NCH 2 CH 3). • Plausible reaction pathways for the formation of Ln(NCH 2 CH 3). Ln (Ln = La and Ce) atom reactions with ethylamine are conducted in a pulsed laser vaporization supersonic molecular beam source. Dehydrogenation and association metal-containing species are observed with time-of-flight mass spectrometry, and the dehydrogenated Ln ethylimido species in the formula Ln(NC 2 H 5) are characterized by single-photon mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and a scalar relativity correction, electron correlation, and spin-orbit coupling through multiconfiguration quasi-degenerate second-order perturbation theory for the Ce species. The MATI spectrum of lanthanum ethylimido La(NCH 2 CH 3) has a single vibronic band system from the ionization of the doublet ground state with the La 6s1 configuration, whereas that of the cerium ethylimido Ce(NCH 2 CH 3) displays two vibronic band system from the ionization of the two lowest-energy spin-orbit coupling states with the Ce 4f16s1 configuration. Both Ln ethylimido complexes are formed by the thermodynamically and kinetically favorable concerted dehydrogenation of the amino group. Two additional isomers of Ln(NC 2 H 5) include a four-membered metallacycle Ln(NHCH 2 CH 2) from the dehydrogenation of the amino and methyl groups and a three-membered cycle Ln(NHCHCH 3) from the dehydrogenation of the amino and methylene groups. The cyclic isomers are not observed experimentally as they are not populated under the experimental conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Dissociation of 0.5–1.9 eV supersonic CH 3 Cl molecules on Cu 2 O(111). • Cl as the dominant adsorbed species coming from the dissociative scattering of CH 3 Cl. • Identification of the adsorbed species using SR-XPS. • Comparison of the reactivity between bulk Cu 2 O(111) and precursor Cu-oxide grown on Cu(111). To examine the elementary steps of the Rochow-Müller process we placed copper oxides, viz., Cu 2 O(111) and the bulk Cu 2 O precursor "29"-structure on Cu(111), under supersonic molecular beams (SSMB) of CH 3 Cl. The SSMB energies range from 0.5-1.9 eV. We employed X-ray photoemission spectroscopy (XPS) in conjunction with synchrotron radiation (SR) to determine the resulting adsorbed species present. We identified two reaction paths, viz., Reaction I and Reaction II. Reaction I involves dissociative adsorption of CH 3 Cl. In Reaction II, CH 3 Cl also dissociates, but with Cl as the dominant adsorbed species (higher than that of adsorbed carbonaceous species, as observed for Reaction I). For the incident energies and exposure conditions considered, we found Reaction II as the dominant reaction path for CH 3 Cl reaction on both Cu 2 O(111) and the "29"-structure on Cu(111). [ABSTRACT FROM AUTHOR]

We present Raman spectroscopy of the polycrystalline Si and Ge films formed by molecular beam deposition on a dielectric substrate. Structural properties of the poly– films have been studied by XRD and TEM. The Raman spectra of poly– Si films demonstrate both a downward shift and an asymmetrical broadening of the vibrational band near 520 cm−1, while only a symmetrical broadening of the band at 300 cm−1 is observed in the spectra of poly– Ge. The Raman line shape has been modeled within the framework of phonon confinement theory, taking into account the sizes of coherent scattering domains estimated using XRD and the influence of extended defects on peak broadening. Phonon dispersion and density of phonon states have been simulated using density functional theory. It has been found that grain boundaries, rather than other extended defects such as twins (multiple twins, twin boundaries), lead to significant changes in phonon dispersion and density of phonon states. • Asymmetrical broadening of the main band is observed in the Raman spectra of poly-Si. • Symmetrical broadening of the main band is observed in the Raman spectra of poly-Ge. • Phonon confinement theory is used to model asymmetrical Raman band broadening. • Phonon confinement is associated with grain boundaries rather than twins. [ABSTRACT FROM AUTHOR]

Lipid peroxidation, a self-propagating chain reaction that oxydates lipid molecules, contributes to harmful effects of ionizing radiation. A decrease in peroxidation at higher dose rates could play a role in the FLASH sparing effect. We explored how lipid peroxidation induced by FLASH (>100 Gy/s) and conventional (CONV, <0.2 Gy/s) radiation depends on lipid concentration and content of polyunsaturated fatty acids (PUFA). Additionally, we investigated the correlation between the lipid peroxidation and the main beam parameters characterizing pulsed electron beams, namely the dose per pulse (DR p) and the average dose rate (DR av). We employed phosphatidylcholine (PC) liposomes as a model of biological membranes. Suspensions of liposomes containing different proportions of linoleic acid (LA) were prepared at various concentrations and irradiated at FLASH and CONV dose rates. Additionally, the liposomes were exposed to beams characterized by diverse combinations of DR p and DR av. The extent of lipid peroxidation was assessed by monitoring oxygen consumption (ΔpO 2) and measuring the yield of malondialdehyde (MDA), and in certain instances, of lipid peroxides (LOOH). Regardless of the radiation dose, liposome concentration or LA content, ΔpO 2 and the yield of MDA were significantly lower for FLASH than for CONV irradiation. Increase in the proportion of readily oxidizable LA in the lipid had negative effect on the MDA yield but correlated positively with ΔpO 2 and LOOH yield. Exposing liposomes to beams operating at different pulse repetition frequencies, while keeping the total dose and DR p constant, resulted in markedly different ΔpO 2 and MDA yields. In contrast, DR av was found to exhibit stable correlation with both MDA yield and ΔpO 2. Irradiation at FLASH dose rates produces lower yield of lipid peroxidation in PUFA-containing artificial PC membranes than CONV irradiation under all tested conditions. Time-averaged dose rate, in contrast to pulse dose rate, was the critical parameter determining the level of lipid peroxidation induced by pulsed electron beams. • Lipid peroxidation after FLASH is decreased compared to CONV regardless of lipid concentration and proportion of PUFA. • Main determinant of lipid peroxidation yield for pulsed electron beams is average dose rate. • Lipid peroxidation yield is poorly correlated with pulse dose rate/dose per pulse. • Under irradiation, lipids with lower PUFA content consume less oxygen but yield more MDA. [ABSTRACT FROM AUTHOR]

The scattering of gases on solid surfaces plays a vital role in many advanced technologies. In this study, the scattering behavior of helium on graphene surfaces was investigated, including the thermal accommodation coefficient (TAC), outgoing zenith angle of helium, bounce number, and interaction time. First, we performed molecular dynamics simulations to describe the incident angle-resolved behaviors, and showed that the scattering is highly dependent on the zenith angle of incident helium but insensitive to the azimuthal angle. The contribution of the normal velocity component of the incident helium dominated the energy transfer. The nonlinear relationship of the parameters to the zenith angle of the incident helium could be suppressed by increasing the graphene temperature or decreasing the speed of the incident helium. Subsequently, the scattering performance considering all gas molecules in the hemispherical space was evaluated using the Monte Carlo method with angle-resolved results. The result showed that the TAC, its nominal components, and the zenith angle of the scattered helium increased with higher speeds of incident helium and lower temperatures of graphene. This study should provide a fundamental understanding of energy transfer between gas and two-dimensional materials and guidelines to tune the scattering behavior between them. [ABSTRACT FROM AUTHOR]

The separation induced by shock wave/boundary layer interactions (SWBLI) is detrimental to the performance of the flow field, and thus, needs to be reduced by using passive or active approaches. In this study, the authors numerically evaluate flow control induced by steady and pulsed micro-jets to capture the mechanism of control of three-dimensional (3D) SWBLIs. The volume of the separation zone is accurately calculated to assess the control effect. The results predicted by the 3D Reynolds-averaged Navier–Stokes equations coupled with the two-equation κ-ω turbulence model of shear stress transport show that the proposed method of using steady or pulsed micro-jets can significantly reduce the volume of the separation zone induced by shock wave/boundary layer interactions. The best comprehensive effect of control over the flow field was obtained by using a high frequency angled jet—namely, case P5—as it reduced the volume of the separation zone by 19.43% with only a small loss in the total pressure. The upwash and downwash motions induced by the streamwise counter-rotating vortex pairs of the jet constituted a key factor influencing the control of the separation zone. [ABSTRACT FROM AUTHOR]

We demonstrate optical cycling and laser cooling of a cryogenic buffer-gas beam of calcium monohydride (CaH) molecules. We measure vibrational branching ratios for laser cooling transitions for both excited electronic states A and B. Furthermore, we measure that repeated photon scattering via the A ← X transition is achievable at a rate of ∼ 1.6 Ă— 1 0 6 photons sâˆ'1 and demonstrate interaction-time limited scattering of ∼ 200 photons by repumping the largest vibrational decay channel. We also demonstrate a sub-Doppler cooling technique, namely the magnetically assisted Sisyphus effect, and use it to cool the transverse temperature of a molecular beam of CaH. Using a standing wave of light, we lower the transverse temperature from 12.2(1.2) mK to 5.7(1.1) mK. We compare these results to a model that uses optical Bloch equations and Monte Carlo simulations of the molecular beam trajectories. This work establishes a clear pathway for creating a magneto-optical trap (MOT) of CaH molecules. Such a MOT could serve as a starting point for production of ultracold hydrogen gas via dissociation of a trapped CaH cloud. [ABSTRACT FROM AUTHOR]

An intense source of cold hydrogen atoms in a supersonic beam is presented. H and D atoms are produced from pure samples of H2 and D2 using a barrier discharge near the orifice of a cryogenic pulsed valve. The atoms are entrained in the supersonic expansion of the precursor molecules and cool down to translational temperatures as low as ∼ 15 mK. The H-atom density at a distance of 1.2 m from the valve orifice is estimated to be around 108 cmâˆ'3. The mean velocity of the supersonic beam containing the H (D) atoms can be adjusted between 2600 and 1200 m sâˆ'1 (between 1850 and 820 m sâˆ'1). The barrier discharge also produces H n + and D n + ions with n ranging from 2 to 8, which can be deflected off the beam by electric fields. The use of this H-atom source in spectroscopic measurements is demonstrated by an investigation of the Stark effect in the 1sâ€"2s two-photon transition of H and D. A near-Fourier-transform-limited pulsed laser generating pulses of UV radiation of adjustable pulse length between 10 and 200 ns near 243 nm is used to record spectra with full resolution of the hyperfine structure in the s states, providing a textbook example of the Stark effect in the simplest set of near-degenerate states of one-electron atoms. [ABSTRACT FROM AUTHOR]

This work evaluates the passivation efficacy of thermal atomic layer deposited (ALD) Al2O3 dielectric layer on self-catalyzed GaAs1- x Sb x nanowires (NWs) grown using molecular beam epitaxy. A detailed assessment of surface chemical composition and optical properties of Al2O3 passivated NWs with and without prior sulfur treatment were studied and compared to as-grown samples using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature photoluminescence (PL) spectroscopy. The XPS measurements reveal that prior sulfur treatment followed by Al2O3 ALD deposition abates IIIâ€"V native oxides from the NW surface. However, the degradation in 4K-PL intensity by an order of magnitude observed for NWs with Al2O3 shell layer compared to the as-grown NWs, irrespective of prior sulfur treatment, suggests the formation of defect states at the NW/dielectric interface contributing to non-radiative recombination centers. This is corroborated by the Raman spectral broadening of LO and TO Raman modes, increased background scattering, and redshift observed for Al2O3 deposited NWs relative to the as-grown. Thus, our work seems to indicate the unsuitability of ALD deposited Al2O3 as a passivation layer for GaAsSb NWs. [ABSTRACT FROM AUTHOR]

Proteins with a changeable conformation, such as polymerases, play a very important role in various life activities. Their conformational changes can be reflected in their structural size and flexibility, which may influence their transport kinetics. Recently, solid-state nanopore sensors have been widely applied to characterize the conformation of proteins and other complex structures as sensitive and high throughput single-molecule detectors. In this work, we used a SiN nanopore sensor to study the conformational changes between the Klenow fragment (KF) and its monomer complex with a DNA substrate (KF-DNA). By calculating their hydrodynamic radii, pore volume, the duration of translocation events, drift velocity, and molecular dynamics simulations, we found that the KF-DNA monomer complex has a tighter structure and transports slower. The study performed here can be potentially used to identify single polymerases in real time and may ultimately reveal conformation changes and the interaction between polymerases and their substrates. [ABSTRACT FROM AUTHOR]

The effect of growth pressure on the properties of β-Ga2 O3 thin films epitaxial on c-plane sapphire substrate with 6° oblique cut angle by plasma-assisted molecular beam epitaxy were systematically studied. All of the epitaxial films present (201) orientated single-crystalline structure with smooth surface morphology. In addition, the crystalline quality and growth rate increase gradually with the increase of the growth pressure, as demonstrated by X-ray diffraction and scanning electron microscopy characterizations. According to the X-ray photoelectron spectroscopy measurement results, the percentage of oxygen vacancy and Ga3+ oxidation states decrease and increase, respectively, with increasing growth pressure, resulting in the increment of atomic ratio of O to Ga. Moreover, through the calculation of Tauc formula and Urbach tail model, the results show that the optical band gap of the films increase from 4.94 eV to 5.00 eV, while Urbach energy decreases from 0.47 eV to 0.32 eV. These results suggest that the crystal quality and optical property of β-Ga2O3 were improved by increasing the growth pressure. [ABSTRACT FROM AUTHOR]

Plasma catalysis is a promising approach to further enhance the conversion of methane into value-added products such as methanol. In this work, the mechanisms enabling the conversion of methane to CO, CO2 and methanol enabled by plasma-enhanced catalysis were investigated. A catalyst reactor was incorporated downstream of the plasma jet to enable the separation between plasma generation and the catalyst bed. An enhancement in CH3OH and CO2 production was observed for the shortest distance between the plasma and catalyst compared to the plasma-only case. Plasma-enabled gas heating was shown not to be responsible for the observed synergy while a gas temperature increase as low as 30–40 K significantly impacted desorption rates of CH3OH/C2H5OH on alumina particles. Correlations between molecular beam mass spectrometry (MBMS) measurements at the inlet and outlet of the catalytic reactor suggest that the observed synergistic effect was caused by radical species most likely the CH3O2 radical. This study shows that surface reactions induced by radicals such as alkylperoxy radicals might play an important role in surface reactions in plasma-catalysis. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the Fe K-shell lines in the supernova remnant W 51 C and hard X-ray sources in the proximity. We measure the intensities of the Fe  i Kα and Fe  xxv Heα lines at 6.40 and 6.68 keV, respectively, and find that the intensity of the 6.68 keV line is consistent with the background level expected from previous studies, while that of the 6.40 keV line is higher at the significance level of 2.0σ. Given the presence of gamma-ray emission and high ionization rate point spatially coincident with the remnant, we conclude that the enhanced 6.40 keV line most likely originates from the interaction between low-energy cosmic rays and molecular clouds. Also, we discover an enhanced 6.68 keV line emission from the compact H  ii region G49.0−0.3 at a significance level of 3.4σ. Spectral analysis reveals that the temperature and abundance of the thermal plasma with the 6.68 keV line is |$kT=3.0^{+0.8}_{-0.7}$|  keV and Z = 0.5 ± 0.2 solar, respectively. These values are explained by the thermal plasma generated by the stellar winds of O stars. [ABSTRACT FROM AUTHOR]

Metronidazole belongs to the class of nitroimidazole molecules and has been considered as a potential radiosensitizer for radiation therapy. During the irradiation of biological tissue, secondary electrons are released that may interact with molecules of the surrounding environment. Here, we present a study of electron attachment to metronidazole that aims to investigate possible reactions in the molecule upon anion formation. Another purpose is to elucidate the effect of microhydration on electron-induced reactions in metronidazole. We use two crossed electron/molecular beam devices with the mass-spectrometric analysis of formed anions. The experiments are supported by quantum chemical calculations on thermodynamic properties such as electron affinities and thresholds of anion formation. For the single molecule, as well as the microhydrated condition, we observe the parent radical anion as the most abundant product anion upon electron attachment. A variety of fragment anions are observed for the isolated molecule, with NO2− as the most abundant fragment species. NO2− and all other fragment anions except weakly abundant OH− are quenched upon microhydration. The relative abundances suggest the parent radical anion of metronidazole as a biologically relevant species after the physicochemical stage of radiation damage. We also conclude from the present results that metronidazole is highly susceptible to low-energy electrons. [ABSTRACT FROM AUTHOR]

The thickness uniformity of the molecular beam epitaxial film is one of the most important factors affecting the quality of the film, and it is mainly influenced by the angular distribution of the molecular source, which is mainly determined by the inner wall shape of the crucible. In this paper, an optimization method based on particle swarm optimization, Monte Carlo simulations, and an artificial neural network is proposed, aiming at optimizing the epitaxial film uniformity in the molecular beam epitaxy process. The optimum angular distribution of an effusion source is obtained by using the method of particle swarm optimization for a given geometric configuration. The Monte Carlo method is used to simulate the particle evaporation process to obtain the relationship between the shape parameters of the crucible inner wall and the particle angular distribution. The optimum crucible shape parameters are subsequently obtained under a particular apparatus geometric configuration by using the artificial neural network according to the above relationship and the desired optimum angular distribution. Finally, the optimized results are compared by experiments. [ABSTRACT FROM AUTHOR]

Enhancing the stability and durability of metal-organic frameworks (MOFs) is vital for practical applications because many promising MOF materials suffer from phase transitions and/or structural decompositions with humidity being a particularly damaging condition. In mechanical engineering, the frame of buildings and furniture can be stabilized significantly by installing a truss beam. Employing the same principle, we functionalized the organic component of MOF-5 to contain a carbazole moiety that can act as a molecular truss beam by reaching across the corner and forming a stable π–π interaction with a phenyl group on the edge position of the MOF-skeleton. This structural support enhanced the stability of the MOF substantially, allowing the designed MOF to maintain compositional integrity under steam conditions at 90 °C for ~5 days. The unmodified MOF-5 shows clear signs of structural collapse after ~1 h. [ABSTRACT FROM AUTHOR]

In this article, the normally- OFF oxidized Si-terminated (C–Si) diamond metal–oxide–semiconductor field-effect transistors (MOSFETs) with as-deposited 0.5-nm silicon on diamond annealed at high temperature as the subsurface p-channel were presented for the first time. A novel method utilizing both a metal mask to realize the regrown heavily boron-doped (001) diamond layer first (p+-diamond-first) and a molecular beam deposition (MBD) method to procure atomic-scale silicon deposition was achieved. Scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) element mapping results suggest that the C–Si diamond/Al2O3 interface is quite continuous and atomically flat. A remarkably high threshold voltage (${V}_{\text{TH}}$) of −10 V and a maximum drain current density (${I}_{D\_{}{\text{MAX}}}$) of −156 mA/mm are simultaneously achieved in the fabricated devices. The devices with different source and drain (S/D) distances ($L_{\text{SD}}$) deliver robust ${V}_{\text{TH}}$ results and feature low OFF-state S/D leakage current $\vert {I}_{\text{leakage}}\vert $ of ~ $6\times10$ −6 mA/mm at ${V}_{\text{GS}}$ = 0 V. The extracted field-effect mobility is as high as 127 cm2 $\cdot \text{V}$ −1 $\cdot \text{s}$ −1 and the interface state density is as low as $4.35\times10$ 12 eV−1 $\cdot $ cm−2. These competitive results reveal that this first attempt of employing the combination of p+-diamond-first and MBD approaches promotes the integration of the advanced silicon manufacturing process with wide bandgap diamond material for power applications. [ABSTRACT FROM AUTHOR]

The structural information of 3‐cyanoindole ammonia cluster, 3CI(NH3)1, in molecular beams was investigated in the gas phase. We obtained UV–UV hole‐burning spectrum (UV–UV HB) to determine the number of conformers present in the molecular beams and examine their spectral features. As a result, single conformer of 3CI(NH3)1 was observed in the mass‐selected one‐color resonant two‐photon ionization (1C‐R2PI) spectroscopy. The origin band of 3CI(NH3)1 in the R2PI spectrum is redshifted by 122 and 71 cm−1 compared to those of the 3CI monomer and 3CI 1:1 water cluster, 3CI(H2O)1, respectively. The fully optimized geometries, relative energies, transition energies, binding energies, and electrostatic potential (ESP) of the 3CI monomer, 3CI(H2O)1, and 3CI(NH3)1 clusters were calculated at the B3LYP and TD‐B3LYP methods with the 6‐311++(d,p) basis set. The observed spectra are compared with the predictions of time‐dependent density functional theory calculations. [ABSTRACT FROM AUTHOR]

In this work, the effects of arsenic (As) flux used during gallium (Ga) seed droplet consumption and the post-growth annealing on the optical, electrical, and microstructural properties of self-catalyzed molecular beam epitaxially grown tellurium (Te)-doped GaAs nanowires (NWs) have been investigated using a variety of characterization techniques. NWs using the same amount of As flux for growth of the seed droplet consumption demonstrated reduced density of stacking faults at the NW tip, with four-fold enhancement in the 4K photoluminescence (PL) intensity and increased single nanowire photocurrent over their higher As flux droplet consumption counterparts. Post-growth annealed NWs exhibited an additional low-energy PL peak at 1.31 eV that significantly reduced the overall PL intensity. The origin of this lower energy peak is assigned to a photocarrier transition from the conduction band to the annealing assisted Te-induced complex acceptor state (TeAsVGa−). In addition, post-growth annealing demonstrated a detrimental impact on the electrical properties of the Te-doped GaAs NWs, as revealed by suppressed single nanowire (SNW) and ensemble NW photocurrent, with a consequent enhanced low-frequency noise level compared to as-grown doped NWs. This work demonstrates that each parameter in the growth space must be carefully examined to successfully grow self-catalyzed Te-doped NWs of high quality and is not a simple extension of the growth of corresponding intrinsic NWs. [ABSTRACT FROM AUTHOR]

Most experimental methods for studying the kinetics of surface reactions – for example, temperature programmed desorption (TPD), molecular beam relaxation spectrometry (MBRS) and velocity‐resolved kinetics (VRK) – employ detection schemes that require thermal desorption. However, many adsorbates – for example reaction intermediates – never leave the surface under reaction conditions. In this paper, we present a new method to measure adsorbate concentrations on catalytic surfaces and demonstrate its utility for studying thermal desorption kinetics. After a short‐pulsed molecular beam deposits CO or NH3 on Pt (111), the surface is irradiated with an ultrashort laser pulse that induces desorption. Another tightly focused ultrashort laser pulse ionizes the gas‐phase molecules by a non‐resonant multiphoton process and the ions are detected. This two‐laser signal is then recorded as a function of time after the dosing molecular beam pulse and decays exponentially. First‐order thermal desorption rate constants are obtained over a range of temperatures and found to be in good agreement with past reports. Ion detection is done mass selectively with ion‐imaging, dispersing the gas phase molecules by their velocities. Since laser‐induced desorption (LID) produces hyperthermal gas phase molecules, they can be detected with little or no background. This approach is highly surface‐specific and exhibits sensitivity below 10−4 ML coverage. Because the signals are linearly proportional to adsorbate concentration, the method can be employed at lower temperatures than VRK, whose signal is proportional to reaction rate. [ABSTRACT FROM AUTHOR]

Gas chromatography–mass spectrometry (GC‐MS) with Cold EI is based on interfacing GC and MS with a supersonic molecular beam (SMB) and sample compounds ionization with a fly‐through ion source as vibrationally cold compounds in the SMB (hence the name Cold EI). We explored the use of nitrogen and hydrogen as carrier and make‐up gases with Cold EI and found:Nitrogen is very effective in cooling compounds in SMB and while helium requires 60 ml/min nitrogen provides effective cooling with only 7–8 ml/min combined column and make‐up flow rate. Hydrogen is less effective than helium and requires higher flow rates.The transition from helium to nitrogen (or hydrogen) is simple and fast and requires just closing the helium valve and opening the nitrogen valve.The same column used with helium can be used with nitrogen or hydrogen.The same elution times could be obtained with nitrogen or hydrogen as with helium.The GC separation with nitrogen was reduced compared with helium and peak widths were increased by an average factor of 1.5 for similar elution times. Hydrogen provided ~0.7 narrower peak widths than helium.The signal with nitrogen was reduced compared with helium by an average factor of 3.3 and the signal loss was reduced with higher compounds mass. With hydrogen the signal loss was about a factor of 1.5 but the baseline noise was higher thus with similar S/N as with nitrogen.USEPA 8270 semivolatile mixture was easily analyzed with both nitrogen and hydrogen carrier gases. [ABSTRACT FROM AUTHOR]

Resistive switching properties based on molecular beam epitaxy-grown monolayer hexagonal boron nitride (h-BN) atomristors are studied by using metal insulator metal configurations with different electrode materials. Au/monolayer h-BN/Ni devices demonstrate a forming-free bipolar resistive switching (BRS) behavior, a good endurance with up to 97 cycles at a high compliance current of 100 mA, an average on/off ratio of 103, and a low set/reset voltage variability. Metal/monolayer h-BN/graphite/Co devices exhibit self-compliant current BRS characteristics. Both metal/h-BN/Ni and metal/h-BN/graphite/Co devices show the coexistence of BRS, unipolar resistive switching (URS), and nonvolatile threshold switching (TH) modes. The formation of conductive filaments is attributed to the diffusion and trapping of metal ions on the defect sites driven by the electric field, while the rupture is driven by the electric field in BRS and by Joule heating in URS and TH modes. [ABSTRACT FROM AUTHOR]

Optoelectronic devices in the mid-infrared have attracted significant interest due to numerous potential applications in communications and sensing. Molecular beam epitaxial (MBE) growth of highly doped InAs has emerged as a promising "designer metal" platform for the plasmonic enhancement of mid-infrared devices. However, while typical plasmonic materials can be patterned to engineer strong localized resonances, the lack of lateral control in conventional MBE growth makes it challenging to create similar structures compatible with monolithically grown plasmonic InAs. To this end, we report the growth of highly doped InAs plasmonic ridges for the localized resonant enhancement of mid-IR emitters and absorbers. Furthermore, we demonstrate a method for regaining a planar surface above plasmonic corrugations, creating a pathway to epitaxially integrate these structures into active devices that leverage conventional growth and fabrication techniques. [ABSTRACT FROM AUTHOR]

The interactions among geodesic acoustic modes (GAMs), mean flow, and mean flow shear were investigated using Langmuir probe arrays under periodic supersonic molecular beam injection (SMBI) during L-mode discharges in HL-2A tokamak. Results of the SMBI fueling process can be described as follows. In Phase I, immediately following beam injection, the electric field (Er) and temperature (Te) were found to be the most sensitive plasma parameters and decreased abruptly with an increase in the intensity of the turbulence. In Phase II, Er increased significantly, and the frequency of the GAMs also increased. In Phase III, Er gradually increased until the next SMBI pulse commenced, whereas the intensity of the GAMs decreased. [ABSTRACT FROM AUTHOR]

High power single mode wafer-fused 1300-nm VCSELs with a gain region based on InGaAs/InAlGaAs short period superlattice are fabricated. An InP-based optical cavity and two AlGaAs/GaAs distributed Bragg reflector heterostructures were grown by molecular beam epitaõy. The current and optical confinement is provided by a lateral-structured buried tunnel junction with etching depth of $\sim 25$ nm. It is shown that optimal diameter of the buried tunnel junction for high-power single mode emission is $\sim 5$ - $6~\mu \text{m}$. The VCSEL demonstrates more than 6 mW single mode continuous-wave power and a threshold current less than 1.5 mA at 20 °C. The output optical power exceeds 1 mW at 85 °C. A -3dB modulation bandwidth up to 8 GHz and 6 GHz is obtained at 20 °C and 85 °C, respectively. The gain coefficient of $\sim 650$ cm−1 and the transparency current density of $\sim 630$ A/cm2 are estimated at zero gain-to-cavity detuning (\sim 60 °C). The ultimate low internal optical losses about 0.08 % per round-trip (distributed losses ~3.2 cm−1) at 20 °C and 0.13 % per round-trip (distributed losses ~5.5 cm−1) at 100 °C were obtained. [ABSTRACT FROM AUTHOR]

Using the example of metal clusters, an experimental setup and procedure is presented, which allows for the generation of size and charge-state selected polyanions from monoanions in a molecular beam. As a characteristic feature of this modular setup, the further charging process via sequential electron attachment within a three-state digital trap takes place after mass-selection. In contrast to other approaches, the rf-based concept permits access to heavy particles. The procedure is highly flexible with respect to the preparation process and potentially suitable for a wide variety of anionic species. By adjusting the storage conditions, i.e., the radio frequency, to the change in the mass-to-charge ratio, we succeeded in producing clusters in highly negative charge states, i.e., Ag 8 0 0 7 − . The capabilities of the setup are demonstrated by experiments extracting electronic and optical properties of polyanionic metal clusters by analyzing the corresponding photoelectron spectra. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to assess the ocular morbidity due to delayed presentation in glaucoma patients because of COVID lockdown. Methodology: This was a retrospective study of 15 cases presented to us between October 2020 and February 2021. Cause of glaucoma in our study group was either primary angle closure, pseudoexfoliation, lens-induced glaucoma, or neovascular glaucoma. The cause of delayed presentation was identified and patients were treated with antiglaucoma medications, Nd-Yag laser, and surgery as per the standard treatment protocol. Results: With both medical and surgical intervention, some useful vision was restored in five cases while in rest it was not salvageable. The vision in the affected eye ranged from 6/60 in Snellen's chart to perception of light and projection of rays positive. Better results were achieved in angle, closure, and lens-induced glaucoma cases as compared to neovascular glaucoma cases. Conclusion: The time of presentation in such cases is as important as the etiopathogenesis. We are left with limited treatment options if the presentation is late. The lockdown ended but it unraveled quite a few instances of disease presentation which were totally preventable under normal circumstances. Introspection on finding out newer and proactive methods to reach people suffering from such irreversible but preventable diseases is the need of the day especially when preventable but irreversible diseases like glaucoma are considered. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigation of iron nanoparticles in condensates of 10…43 wt. % Fe–NaCl system, produced by electron beam evaporation and simultaneous condensation of Fe and NaCl molecular beams in vacuum (EB-PVD method). Transmission electron microscopy, X-ray phase analysis, dynamic light scattering and vibration magnetometry were used to study the structure and dimensions of nanoparticles in Fe–NaCl condensates, their phase and chemical composition, and magnetic properties. Size of Fe3O4 nanoparticles in the condensates, depending on their synthesis temperature, and nanoparticle crystallite size were determined, depending on iron concentration in the condensates. The influence of the quantity of iron in the condensates on the size of nanoparticle crystallites is shown. According to X-ray phase analysis, the size of Fe3O4 crystallites in the concentration range of 2…15 at. % Fe is within 3…14 nm, and in the range of 20…30 at. % Fe it is equal to 17…22 nm. Average size of Fe3O4 crystallites (8…15 nm) produced at substrate temperature of 45 °C, increases to 25…40 nm with increase of substrate temperature (410 °С). It should be noted that in the nanoparticles the pure iron phase is revealed at more than 20 at. % Fe content in the condensate. It was proved that the condensation temperature can be regarded as a reliable factor for regulation of particle size in the technological process. The distribution of hydrodynamic size of Fe3O4 nanoparticle aggregates in water colloids with dextran was studied. Increase of saturation magnetization and coercive force of Fe–NaCl condensates with magnetite nanoparticles at increase of iron content was determined. Ref. 21, Tabl. 1, Fig. 7. [ABSTRACT FROM AUTHOR]

Radicals are abundant in a range of important gas-phase environments. They are prevalent in the atmosphere, in interstellar space, and in combustion processes. As such, understanding how radicals react is essential for the development of accurate models of the complex chemistry occurring in these gas-phase environments. By controlling the properties of the colliding reactants, we can also gain insights into how radical reactions occur on a fundamental level. Recent years have seen remarkable advances in the breadth of experimental methods successfully applied to the study of reaction dynamics involving paramagnetic species—from improvements to the well-known crossed molecular beams approach to newer techniques involving magnetically guided and decelerated beams. Coupled with ever-improving theoretical methods, quantum features are being observed and interesting insights into reaction dynamics are being uncovered in an increasingly diverse range of systems. In this highlight article, we explore some of the exciting recent developments in the study of chemical dynamics involving paramagnetic species. We focus on low-energy reactive collisions involving neutral radical species, where the reaction parameters are controlled. We conclude by identifying some of the limitations of current methods and exploring possible new directions for the field. [ABSTRACT FROM AUTHOR]

In this computational work, we describe the nano-pumping process of carbon nanotube (CNT) with fullerene molecule displacement with molecular dynamics (MD) approach. Technically, for the simulation of CNT and fullerene molecule, we use Tersoff force-field and SPC model implemented for H2O molecules. The result of equilibrium process of these structures shows the good stability of them which arises from the appropriate settings in our MD simulations. Further, to describe the CNT nano-pumping process in the presence of various heat flux and external electric field, we calculate the velocity, translational/rotational components of fullerene kinetic energy, temperature/pressure/density profiles, net flux, and molecular orientation. Numerically, by increasing of external heat flux, the nano-pumping time varies from 85.30 to 75.44 ps, respectively. Furthermore, the external electric field in nano-pumping process is an important parameter and we decrease the nano-pumping time to 66.87 ps by this external field optimization. [ABSTRACT FROM AUTHOR]

Effective radiation–collision involvement of molecules that do not absorb laser radiation in resonance with a laser field in a two-component molecular medium that includes molecules absorbing laser radiation and is subjected to intense infrared laser radiation has been detected. Experiments have been performed with the CF2HCl/CF3Br mixture (at the 1/1 pressure ratio), where molecules are under nonequilibrium thermodynamic conditions in a shock wave, which has been formed in front of the solid surface on which a gas-dynamically cooled intense pulsed molecular beam is incident. Molecules have been excited by the pulsed radiation of a СО2 laser. A method has been described and the first results have been reported. Effective dissociation of CF2HCl molecules (with the yield β ≥ 10–15%) in the CF2HCl/CF3Br mixture irradiated by the CO2 laser detuned by more than 15–25 cm–1 from the center of the infrared absorption band of CF2HCl molecules vibrationally cooled in the shock wave has been detected at quite low excitation energy densities (Φ ≤ 0.5–1.0 J/cm2) at which dissociation of CF2HCl molecules in a pure gas hardly occurs. The results can be applied to separate isotopes using the method of isotope-selective infrared laser dissociation of molecules. [ABSTRACT FROM AUTHOR]