Emissivity of the main greenhouse gases

Based on the high-resolution data on the absorption lines of gases from the HITRAN open inter-national database in conjunction with inverse Fourier transform, the autocorrelation function of the total dipole moment of the molecules of the main greenhouse gases, such as H₂O, CO₂, O₃, N₂O, and CH₄, are determined. The spectral absorption coefficient and spectral radiance of these gases in the investigated IR region is calculated. An analysis of the emissivity of each of the gases is performed. An efficiency criterion of IR absorption and emission is introduced, according to which the studies gases are ranked.     

An optically-pumped multigas Far-IR laser

We report here the operation of an optically-pumped multigas Far-IR laser. In our experiment, three different gases (CH₃OH, CH₃Br, CH₃I) were simultaneously introduced into the Far-IR cavity. By adjusting the partial pressures of the gases and by tuning the appropriate CO₂ laser pump line, we were able to obtain the laser action for each one of them as efficiently as is observed when the gases are present by themselves.     

Visible luminescence from HF laser irradiated absorbing gases

We report the observation of visible luminescence from HF laser irradiated absorbing gases. Preliminary studies using NH₃,CH₃OH and CO₂ gases are described.     

Theoretical and experimental investigations on the deposition rate and processes of parallel incident laser-induced CVD

A theoretical analysis of and experimental observations on a parallel incident laser-induced deposition rate are reported. Our theory predicts that the maximum deposition rate depends on the photo-traveling length, the scattering cross section of the reactant gases and their partial pressure. This result is applied to SiO₂ deposition using monosilane and nitrous oxide for reactant gases, and is compared with experimental results. We show that the deposition rate of SiO₂ films as a function of the incident light power and the partial pressure of reactant gases predicted by the present theory well explains our experimental results. A supply-limitation phenomenon of the reactant gases and a method of estimating deposition efficiencies are also discussed.     

Reversible surface structural changes in Pt-based bimetallic nanoparticles during oxidation and reduction cycles

The surface states of supported PtNi nanoparticles treated at alternating O₂ and H₂ atmosphere were studied by X-ray photoelectron spectroscopy. Reversible structural changes at the surfaces of the supported PtNi nanoparticles in response to reaction gases were observed, showing NiO-rich surface in oxidizing gases and Pt-rich surface in reducing gases. The dynamic behaviors can be attributed to two opposite gas-driven mass transport processes at bimetallic particle surfaces, including surface segregation of Pt at the bimetallic particles in H₂ and encapsulation of the particles by NiO in O₂. The similar surface structural changes can be observed in other bimetallic catalyst systems, as exemplified in supported PtCu and PtCo nanoparticles.     

Determination of H2S,COS, CS2 and SO2 by an aluminium nitride nanocluster: DFT studies

ABSTRACT

Density functional theory calculations were used to investigate the potential application of an AlN nanocluster in the detection of H₂S, COS, CS₂ and SO₂ gases. In overall, the order of strength of interaction of these gases with the nanocluster is as follows: SO₂ (E_ad?=??17.6?kcal/mol)?>?H₂S (E_ad?=??14.0?kcal/mol)?>?COS (E_ad?=??8.4?kcal/mol)?>?CS₂ (E_ad?=??4.5?kcal/mol). This indicates that by increasing the electric dipole moment, the adsorption energy becomes more negative. We found that the Al₁₂N₁₂ nanocluster may be a promising work function-type sensor for SO₂ gas among the studied gases. Also, it is an electronic sensor for both SO₂ and CS₂ gases but selectively acts between them because of their different effects on the electrical conductivity. It is neither work function-type nor electronic sensor for H₂S and COS gases. The AlN nanocluster benefits from a short recovery time about 7.7?s and 18.0?ms for desorption of SO₂ and CS₂ gases from its surface at room temperature, respectively. It is also concluded that this cluster can work at a humid environment.     

A first-principles insight into Pd-doped MoSe2 monolayer: A toxic gas scavenger

Using first-principles theory, we investigate the Pd-doping effect on the geometric and electronic behaviors of MoSe₂ monolayer, and the adsorption behavior of Pd-MoSe₂ monolayer upon four toxic gases, namely NO, NO₂ SO₂ and H₂S. Desorption property of Pd-MoSe₂ monolayer upon four gases at diverse temperatures is analyzed as well to help explore its potential application. For Pd dopant adsorption onto MoSe₂ monolayer, somewhat n-type doping is determined, which accounts for the increased conductivity for intrinsic MoSe₂ monolayer. The strong adsorption ability and poor desorption performance of Pd-MoSe₂ monolayer upon four gases indicate its large potential as gas scavenger to remove these toxic gases from their surroundings. Moreover, it could be explored as a gas sensor for detection of NO, NO₂ and H₂S as well, given the obvious change in conductivity after gas adsorption based on band structure analysis. Our calculations would be beneficial to understand the TM doping effect on intrinsic MoSe₂ monolayer and to provide a first insight into the potential application as gas sensor or sweeper for Pd-MoSe₂ monolayer.     

Field measurements of volcanic gases using tunable diode laser based mid-infrared and Fourier transform infrared spectrometers

The first field measurements of volcanic gases using mid-IR difference frequency laser spectroscopy are reported. The results were obtained at the summit crater of Masaya volcano, Nicaragua, with the gases being drawn into a multi-pass cell and measured at reduced pressure. Automated sensitive and selective detection of CO₂, SO₂, H^35,37Cl, H₂O, and CH₄ was achieved. Simultaneous measurements obtained with open-path Fourier transform spectroscopy provide a useful comparison of the two optical techniques. We also consider the potential measurement of CO₂ isotopic ratios in volcanic gases using laser-based spectroscopy.     

硅衬底上纳米晶金刚石生长

研究了蚀刻气体对生长在硅衬底上纳米晶金刚石合成的影响.合成方法为热丝化学气相沉积法,衬底温度为550 oC,反应压力为4 kPa. 其中甲烷和氢气分别作为源气体和稀释气体. 氮气、氢气和氨气用作蚀刻气体. 结果表明,仅氢气作为蚀刻气体可获得最佳工艺条件.     

A Hydrocarbon-sensitized Argon Ionization Detector for the Detection of Inorganic Compunds

Noble gas ionization detectors make it possible to determine inorganie trace components in gases. Among the several modes of operation of these detectors the hydrocarbon-sensitized argon detector is a farourable compromise with regard to the relation of the expense to the attainable detection limit. The suitability of this detector for the determination of H₂, O₂, N₂, CH₄ and CO₂, in pure gases is shown.     

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO2 and NH3 gases

In this work, using a two‐dimensional particle‐in‐cell Monte Carlo collision computation method, terahertz (THz) radiation generation via the interaction of two‐colour, ultra‐short, high‐power laser pulses with the polyatomic molecular gases sulphur dioxide (SO₂) and ammonia (NH₃) is examined. The influence of SO₂ and NH₃ pressures and two‐colour laser pulse parameters, i.e., pulse shape, pulse duration, and beam waist, on the THz radiation generation is studied. It is shown that the THz signal generation from SO₂ and NH₃ increases with the background gas pressure. It is seen that the THz emission intensity for both gases at higher laser pulse durations is higher. Moreover, for these polyatomic gases, the plasma current density increases with increase in the laser pulse beam waist. A more powerful THz radiation intensity with a larger time to peak of the plasma current density is observed for SO₂ compared to NH₃. In addition, many THz signals with small intensities are observed for both polyatomic gases. It is seen that for both SO₂ and NH₃ the generated THz spectral intensity is higher at higher gas pressures.     

Interferometric measurements of the dipole polarizability α of molecules between 300 K and 1100 K

The temperature dependence of the dipole polarizability α(λ, T) of free atoms and molecules is determined by precise measurements of the refractive index n of gases in the extended temperature range between 300 K and 1100 K for wavelength λ = 632·99 nm, using a specially constructed Michelson twin interferometer. α of the noble gases is observed to be independent of T. α of the molecular gases H₂, N₂, O₂, and CH₄ increases with increasing temperature by an amount of approximately 1 per cent per 1000 K. These results are in excellent agreement with theoretical predictions. They will be compared to previously measured temperature dependent polarizabilities.     

碳纳米管阴极强流脉冲发射放气质谱分析

借助2 MeV直线感应加速器注入器平台,利用四极质谱仪研究了碳纳米管阴极的强流脉冲发射放气质谱特性. 研究结果表明:在脉冲高压电场下,碳纳米管阴极材料释放出较多的吸附气体,解吸气体又以CO₂,N₂(CO),H₂三种气体居多,这些解吸气体在阴极等离子体形成过程中起着重要的作用. 通过分析解吸气体成分的含量,证明碳纳米管阴极强流脉冲电子发射过程为场致等离子体发射,而不是场致爆炸发射. 关键词： 碳纳米管阴极 强流脉冲发射 质谱分析 场致等离子体发射     

Interaction of different types of nanocages (Al12N12, Al12P12, B12N12, Be12O12, Mg12O12, Si12C12 and C24) with HCN and ClCN: DFT,TD-DFT,QTAIM, and NBO calculations

In this work, the ability of different types of nanocages including Al₁₂N₁₂, Al₁₂P₁₂, Be₁₂O₁₂, B₁₂N₁₂, Si₁₂C₁₂, Mg₁₂O₁₂ and C₂₄ for the adsorption and detection of poisonous gases HCN and ClCN has been investigated, theoretically using the D3 dispersion corrected density functional theory (DFT-D3). The absorption spectra of HCN–nanocage and ClCN–nanocage complexes were calculated by the time-dependent density functional theory (TD-DFT) and compared with the calculated absorption spectrum of isolated nanocage to investigate the ability of nanocage for sensing of HCN and ClCN gases. It was found that the strongest interaction between HCN (ClCN) molecule and nanocage takes place when the molecule is adsorbed via its N atom on the surface of nanocage except for C₂₄. Also, it was shown that the Al₁₂N₁₂ is the best adsorbent for HCN and ClCN gases among the selected nanocages and Si₁₂C₁₂ is the best sensor for the detection of these gases using the electroconductivity and absorption spectroscopy techniques.     

Zn2准分子的形成及其发射特性

通过光学抽运Zn(4s¹S₀—4p³P₁)共振线,在充有惰性气体的Zn蒸气中观察到两个连续的发射谱带。实验辨认它们可能归属于Zn₂准分子³∑_u⁺态,这与理论预言一致。研究谱带的时间与温度特性,以及惰性气体对谱带发射的影响。给出分子形成速率的上限和猝灭速率。结果表明,惰性气体分子在Zn₂准分子的形成及衰变中起了主要作用。 关键词：     

Measurement of the vibrational energy-transfer rates in mixtures of polyatomic molecules

The pressure coefficient of the vibrational deexcitation of methanol molecules caused by collisions with NH₃, CO₂, SF₆ molecules and He atoms is measured by infrared-far-infrared double-resonance spectroscopy. Large coefficients are measured for those buffer gases which increase the output power of far-infrared lasers. For other buffer gases such as NH₃ and CO₂ the measured coefficients are zero within the limits of experimental error. The relevance to measurements on the photoacoustic trace-gas analysis is discussed.     

A Raman system for multi-gas-species analysis in power transformer

We have built a complete Raman detection system for multi-trace-gas diagnosis, which is suitable for analyzing the dissolved gases in electric power system. In the system, a high-sensitivity CCD device connected to a spectrometer is used as the detection unit of the Raman system. A near-confocal cavity is used for improving the detection sensitivity of the system. In the effective spectral range of about 570–710 nm, Raman spectra of eight typical gases are achieved by using this Raman system. The detection limits for different gases have been obtained: 126 ppm for CO₂, 21 ppm for CH₄, 63 ppm for C₂H₄, 42 ppm for C₂H₂, 96.6 ppm for H₂. The detectability of the system satisfies the requirements of gas diagnosis in power transformer.     

Effect of buffer gases on the performance of SO2 trace measurement based on photoacoustic spectroscopy

In this experimental work a laser photoacoustic spectrometer designed and fabricated. System sensitivity for detection of SO₂ and NO₂ was measured. Resonance frequency variation versus pressure increase of Nitrogen, Argon, Helium and Air buffer gases was studied. Results show that, sensitivity of system for SO₂ and NO₂ are 353 ppb and 963 ppb respectively. It was shown that resonance frequency for Nitrogen, Argon, and Air buffer gases was not noticeably varied by buffer gas pressure increasing, but for Helium, resonance frequency not only is not in range of three other gases, but also grows by pressure increasing. The system noises were damped preparing two buffer chambers.     

Data and modeling of negative ion transport in gases of interest for production of integrated circuits and nanotechnologies

We review techniques to prepare, evaluate and apply sets of cross section and transport data for negative ions that are required for the modeling of collisional non-equilibrium plasmas used for processing of microelectronic circuits. We collect and discuss the transport coefficients and cross section sets.We have compiled data for negative ions in CF₄ and CF₄-related negative ions in rare gases. In addition, we consider data for F⁻ and CF₃⁻ in rare gases. Furthermore, we analyze the cross sections of halogen negative ions in rare gases and other molecules. This is followed by the data for SF₆ related ions in SF₆ and in rare gases. The cross section for scattering of O⁻ in O₂ has been derived from the transport data and used to make calculations of the transport properties. Finally we give a brief discussion of the availability of the data for H⁻ ions in H₂. We have derived cross sections in several cases but the basic aim is to show the basic features of transport coefficients. In particular we discuss the need to represent properly some details such as the non-conservative nature of transport coefficients and the anisotropy of diffusion. Application of approximate theories and representations of cross sections are also discussed.