The Sounding of Hydrogen Sulfide Molecules by the Raman Light Scattering Lidar Installed on a Flying Platform

Optics and Spectroscopy - The lidar equation is solved numerically for the Raman backscattering by hydrogen sulfide molecules in the atmosphere and water with concentrations about 1011–1015...     

Lidar Probing of a Mixture of Hydrogen Sulfide and Methane Molecules in the Atmosphere from a Flying Platform

Optics and Spectroscopy - The results of numerical solution of the lidar equation for the Raman scattering on the molecules of a gas mixture of hydrogen sulfide and methane in the 180°...     

Estimation of the characteristics of a promising orbital lidar for space debris monitoring

A preliminary study aimed at estimating the potential of a promising orbital lidar for space debris monitoring has been performed. Estimates of the space debris detection range under different observation conditions with different technical characteristics of lidar have been calculated. It is shown that the detection range for space debris fragments with sizes of 1 to 10 cm in the wavelength range near 0.5 µm depends strongly on the observation conditions, which are determined by the additive-noise level. It is concluded that a promising orbital lidar should contain a laser emitter with a power of several hundreds of watts and a receiving telescope about 0.5 to 1m in diameter. The possibility of using an orbital lidar for recognizing space debris is estimated. It is shown that a recognition probability exceeding 0.8 can be attained for a space debris image containing several tens of pixels and a signal-to-noise ratio above 10.     

Laser sounding of molecular iodine in the atmosphere

The lidar equation for the fluorescence of ¹²⁷I₂ molecules is numerically solved. All the radiation wavelengths of a copper vapor laser are considered with the aim of choosing the one that is the most appropriate for detection of the minimum possible concentration of iodine molecules when this laser is used as a radiation source of a fluorescence lidar.     

The influence of molecular hydrogen on the conductivity of magnesium oxide containing paramagnetic surface defects

MgO with a high concentration of defects was produced by the dehydration of high-purity Mg(OH)₂ and the conductivity was studied in the temperature range 20–250°C. An atmosphere of hydrogen increased the conductivity by up to a factor of 10³ and produced a characteristic conductivity maximum when the sample was heated. The hydrogen interacts with the sample at V¹_i-centers which are located at the surface of the dehydrated material. These centers are supposed to have a catalytic activity, i.e. they decompose hydrogen molecules into atoms and further into electrons and protons which contribute to the current.     

基于铜离子沉积石墨烯涂层锥形光子晶体光纤的硫化氢传感器

提出一种基于铜沉积石墨烯涂层光子晶体光纤马赫-曾德干涉的硫化氢气敏传感器.将45mm光子晶体光纤两端与单模光纤进行拉锥熔接,使得光子晶体光纤的空气孔熔接时形成塌陷层,更好地激发包层模式,形成基于马赫-曾德结构的干涉仪.采用单层石墨烯粉体,加入异丙醇分散液,反复浸涂至光子晶体光纤包层表面形成石墨烯涂层,并沉积铜纳米颗粒,使传感器对硫化氢气体具有高的响应度.实验结果表明,在硫化氢气体浓度为0~60ppm范围内,随着被测气体浓度不断增大,其输出光谱呈现明显蓝移,传感器灵敏度为0.042 03nm/ppm,且线性度良好.该传感器成本低、灵敏度高、结构简单,适用于低浓度硫化氢气体的在线监测.     

Study of vibrational spectra of lanthanum sulphate nonahydrate at different temperatures in the region from 4000–50 cm−1

Infrared spectra of lanthanum sulphate nonahydrate are studied over the 4000–50 cm⁻¹ range. The bands pertaining to different internal and external modes of sulphate ion and water molecules are observed and assigned. It is shown that coordinated water molecules exist at two site symmetries C₁ and C_i, which provides confirmation of crystallographic data. Lattice water is not found in these crystals. The effect of low temperature on librational modes of coordinated water and their lattice vibrations are studied in the 550–50 cm⁻¹ region. The potential force field constants are calculated for rocking, wagging and twisting librational modes of water at 290 K, 80 K and 60 K. The higher value of the potential constant for the rocking mode from the wagging librational mode shows the in-plane bend of the hydrogen bond in lanthanum sulphate crystals.     

Lidar Probing of Raman Scattering by Hydrofluoride Molecules in an Atmospheric Boundary Layer

Journal of Applied Spectroscopy - The lidar equation for Raman scattering of light by hydrogen fluoride molecules is solved in order to select the laser wavelength and lidar parameters and to...     

Diffusion coefficients of hydrogen and deuterium in highly concentrated palladium hydride and deuteride phases

Fick's diffusion coefficients for hydrogen and deuterium were determined in palladium hydride and deuteride in the pressure range of gaseous hydrogen and deuterium from 10¹–10⁴ bar and the temperature range from 208 to 338K. This corresponds to the concentration range H, D/Pd from about 0.8 to near stochiometry. An electrical resistance relaxation method was used experimentally. Einstein's diffusion coefficients were calculated and the activation volumes and energies were evaluated. An attempt is made to interpret the anomalous behaviour of the diffusion coefficient in the low temperature range. The results are presented in terms of a compact formula.     

Plasma parameter diagnosis using hydrogen emission spectra of a quartz-chamber 2.45 GHz ECRIS at Peking University

A quartz-chamber 2.45 GHz electron cyclotron resonance ion source(ECRIS) was designed for diagnostic purposes at Peking University [Patent Number: ZL 201110026605.4]. This ion source can produce a maximum 84 m A hydrogen ion beam at 50 k V with a duty factor of 10%. The root-mean-square(RMS) emittance of this beam is less than 0.12π mm mrad. In our initial work,the electron temperature and electron density inside the plasma chamber had been measured with the line intensity ratio of noble gases. Based on these results, the atomic and molecular emission spectra of hydrogen were applied to determine the dissociation degree of hydrogen and the vibrational temperature of hydrogen molecules in the ground state, respectively. Measurements were performed at gas pressures from 4×10~(-4) to 1×10~(-3) Pa and at input peak RF power ranging from 1000 to 1800 W. The dissociation degree of hydrogen in the range of 0.5%-10% and the vibrational temperature of hydrogen molecules in the ground state in the range of 3500-8500 K were obtained. The plasma processes inside this ECRIS chamber were discussed based on these results.     

Ramsey terms for two-, three-, and four-bond coupling involving 15N and 17O in hydrogen-bonded and nonhydrogen-bonded systems: are coupling constants sensitive to RAHBs?

Ab initio EOM-CCSD/(qzp,qz2p) calculations have been performed on complexes with intermolecular hydrogen bonds involving ¹⁵N and ¹⁷O, and molecules with and without intramolecular hydrogen bonds involving these nuclei. Coupling constants across intermolecular hydrogen bonds are well approximated by the Fermi-contact (FC) term. In general, ^2hJ(X–Y) for intramolecular coupling across X–H^…Y hydrogen bonds are not sensitive to the presence of resonance-assisted hydrogen bonds (RAHBs). However, ^2hJ(O–O) for coupling across the intramolecular hydrogen bond in malonaldehyde is greater than ^2hJ(O–O) for its saturated counterpart, so that ^2hJ(O–O) is sensitive to the presence of the RAHB. This is also the case for the sulphur analogues of malonaldehyde. For these unsaturated hydrogen-bonded molecules, molecules with carboxyl groups, and trans-glyoxal, J is dominated by the paramagnetic spin orbit (PSO) term. For these systems, the primary mode of coupling transmission is through the conjugated chain. For complexes with intermolecular hydrogen bonds, saturated molecules with intramolecular hydrogen bonds, unsaturated and saturated molecules in which the hydrogen bond has been broken, and unsaturated molecules with intramolecular N–H^…N or O–H^…N hydrogen bonds, J is dominated by the FC term. FC domination in hydrogen-bonded systems indicates that the primary transmission mode is across the hydrogen bond.     

Study of the Rod-Like and spherical nano-ZnO morphology on H2S removal from natural gas

The purpose of this work is to study the adsorption of H₂S from gas streams containing He and CH₄ with an emphasis on the influence of the sorbent morphology on the process of adsorption. As an example of the approach, a unique modified nano-ZnO sample with a Rod-like morphology was fabricated and comparatively studied together with a nano-spherical ZnO sample under various conditions. The objective was accomplished applying central composite design (CCD) in order to screen the effects of significant adsorption parameters obtained by Placket-Burman design. Morphology of the sorbent, temperature, space velocity and H₂S feed concentration were initially evaluated. Placket-Burman design experiments showed a wide deviation of adsorption capacity of 0.03-0.24 g H₂S/g ZnO. Results indicated that comparing other parameters Rod like morphology comparing spherical, had significant effect on all four independent H₂S adsorption parameters. Besides that, space velocity and H₂S feed concentration were found to be effective parameters on adsorption of hydrogen sulfide in the range of 4000-8000 h⁻¹ and 0.5-1 mol% respectively. Moreover, experiments revealed a negligible effect of adsorption temperature in range of 150-250 °C. The optimized condition obtained a dynamic capacity of 0.2401 g H₂S/g ZnO at space velocity 4000 h⁻¹ and H₂S feed concentration of 1 mol%. Proceeding our study by significant parameters, analysis of variance (ANOVA) displayed a high coefficient of determination (R²) value of 0.931-0.959, indicating the satisfactory adjustment of the quadratic model.     

Effects of concentrated NaCl and KCl solutions on the behaviour of aqueous peptide bond environment: single-particle dynamics and H-bond structural relaxation

The effects of salt concentrations on the structure, dynamics and hydrogen bond structural relaxation properties of ～1.10 M aqueous N-methylacetamide (NMA) solution at 308 K are studied by classical molecular dynamics simulations. We have considered the concentration range of salts solution from 0.222 to 3.756 M to investigate the behaviour of aqueous environment of peptide bonds in the presence of concentrated NaCl and KCl solution. It is found that the addition of salt solution facilitates the structural breaking of aqueous NMA hydrogen bonds, as a result the number of hydrogen bonds per NMA molecule and their stability decreases. The water and NMA molecule shows slower translational and rotational dynamics with increasing salt concentrations due to additional ion atmospheric friction. Our result shows that the cation–O_NMA radial distribution function decreases whereas the Cl^?─H_NMA radial distribution function increases with ion concentration. On the other hand, the cation–O_water and Cl^?─H_water radial distribution function shows very negligible change with respect to ion concentration. We have also calculated NMA–water and water–water hydrogen bond structural relaxation times. It is observed that the hydrogen bond structural relaxation of O_NMA─H_water is comparatively slower than the H_NMA─O_water hydrogen bond, which can be attributed to higher number and greater stability of the former hydrogen bond than the latter. The change of the dynamical quantities observed here is more prominent in addition of NaCl rather than the KCl solution.     

BS2和BS2-分子的红外光谱和Jahn-Teller效应

Laser ablated boron atoms have been reacted with hydrogen sulfide and the reaction products condensed with argon at 4 K, which gave BS₂, BS₂^-, HSBS, and HBS molecules. Reagent isotopic substitution (H₂S, H₂³⁴S, D₂S, ¹⁰B, ¹¹B) and variation of boron and hydrogen sulfide concentrations have been used to identify the major products. Both BS₂^- and BS₂ were identified as linear molecules with no significant difference in the structure parameters, but the B-S anti-symmetric stretching vibration of BS₂ is significantly lower than that of BS₂^-, which is ascribed to pseudo Jahn-Teller effect. Theoretical calculation was employed to have an insight into the interaction nature of the bonds in the corresponding products.     

Theoretical search for half-metallic material: Y MnS3

Half-metallic material, perovskite sulfide Y MnS₃, is theoretically discovered. Our calculated results show that the ground state is the ferromagnetic state with a high estimated Curie temperature of about 869 K, and the ground-state structure exhibits Pm3m space group with no Jahn–Teller distortion. The ferromagnet behaves as half-metal with an energy gap of 1.30 eV at the Fermi level in the down-spin band. Additionally, Mn ions are in the high-spin state with the chemical valence state of Mn³⁺.     

Possible mechanisms of dielectric relaxation of liquid water and calculation of the temperature dependence of the complex permittivity of water

The spectra of the complex dielectric permittivity and absorption of water (H₂O) in the frequency range 0–1000 cm^?1 are calculated for a wide temperature interval. Using the method of autocorrelation functions, the dielectric response of dipoles rotating in potential wells of three types is found. The majority of dipoles (about 90%) rotate in a deep and comparatively narrow potential well, whose profile resembles an upside-down hat. Such a potential models a molecular structure with strongly bent and/or broken hydrogen bonds. The hat model describes the complex permittivity in the low-frequency (Debye) range and in the range 300–1000 cm^?1. The remaining dipoles (～10%) execute harmonic vibrations of two types: rotational vibrations about the equilibrium direction of a hydrogen bond and translational vibrations along this direction. These types of motion yield the dielectric response in the frequency range 10–300 cm^?1. This response is described by the Lorentz lines in terms of the harmonic oscillator model and the truncated parabola model. The hat–harmonic oscillator–truncated parabola composite model provides good agreement with experimental spectra. The lifetimes of the three types of motion considered are about 10, 0.2, and 0.05 ps, respectively. They characterize (i) tetrahedral translations of molecules accompanied by their rotations, (ii) librations of dipoles in the hatlike potential well, and (iii) elastic interactions of hydrogen-bonded molecules. Based on data of independent methods of investigation, it is concluded that the temperature 300 K is a singular point with respect to the properties of liquid water.     

Hydrogen bonds at silica–CO2 saturated water interface under geologic sequestration conditions

To investigate the effects of sequestration condition on hydrogen bonds between mineral and water, molecular dynamics simulations have been performed. The simulations were conducted at conditions related with geologic sequestration sites: pressure (3.1–32.6 MPa), temperature (318 and 383 K), salinity (0–3 M), salt (NaCl and CaCl₂) and silica surface models Q² (geminal), Q³ (isolated) and amorphous Q³. The hydrogen bonds were classified into four types: silica–silica, silica–dissolved CO₂, silica–water as donors and silica–water as acceptors. The mean numbers of hydrogen bonds for each type were analysed. The results show that: (1) silica surface silanol groups do not form H-bonds with dissolved CO₂ molecules in water (brine); (2) The mean number of hydrogen bonds between silanol groups follows the order: Q² > amorphous Q³ > Q³; (3) The mean number of hydrogen bonds between silanol and water molecules follows the order: Q³ > amorphous Q³ > Q².     

Interaction of polymer matrix and bound water in poly(N-vinylcaprolaktam) films

Interaction of water molecules and the polymer matrix of poly(N-vinylcaprolaktam) (PVCL), depending on temperature (?100 and 50°C) and water concentration (less than 1, 5 and 24 wt %), was investigated using the dielectric spectroscopy method (at 10^?1–10⁷ Hz). The presence of characteristic temperature points of changes of system properties, whose values depend on the quantity of water molecules in the polymer, was identified. It was found that the mechanism of temperature influence and water concentrations changes the characteristics of hydrogen bonds.     

Molecular mechanism of gelation upon the addition of water to a solution of poly(acrylonitrile) in dimethylsulfoxide

The solidification of a solution of poly(acrylonitrile) (PAN) in dimethylsulfoxide (DMSO) upon introduction of water into the solution is studied by Raman spectroscopy. In the absence of water, DMSO molecules are found to produce dipole-dipole bonds with PAN molecules. Upon the introduction of water, DMSO molecules produce hydrogen bonds with it and bands at 1005 and 1015 cm⁻¹ appear in the Raman spectrum, which are assigned to the valence vibrations of S=O bonds involved in the hydrogen bonds. Simultaneously, water molecules produce hydrogen bonds with PAN molecules: R-C≡N...H-O-H...N≡C-R, where R is the carbon skeleton of a PAN molecule. Accordingly, a band at 2250 cm⁻¹ arises in the Raman spectrum, which is assigned to the valence vibrations of C≡N bonds producing hydrogen bonds with a water molecule. When the water content is low and the DMSO concentration is high, the length of the hydrogen bonds varies in wide limits and the band at 2250 cm⁻¹ is wide. As the water content rises, DMSO molecules come out of PAN, the variation of the hydrogen bond length in it decreases (the band at 2250 cm⁻¹ narrows), and a high-viscosity system (gel) arises that consists of PAN molecules bonded to water molecules via “equally strong” hydrogen bonds.     

Infrared Spectra of Crystalline,Glassy and Liquid Methanol at High Pressures

Abstract

Mid-infrared spectra in the range 400–1800 cm^?1 of methanol samples in diamond anvil cells at ambient temperature and pressures up to 11 GPa are reported. The freezing pressure is confirmed to be 3.6 GPa, and the spectra of the resulting metastable glass are very similar to those of the liquid. When maintained at high pressure, the glass spontaneously transforms to an ordered crystalline phase which is stable over the range 3.6 to 11 GPa. Small changes in peak wavenumbers for 14 internal modes as a function of pressure are observed, indicating that distortion of the molecules is minimal. A slight decrease for the C-O-H bending mode is attributed to charge transfer from the molecular 0-H bond to the strengthening intermolecular hydrogen bond.