Rotational and vibrational temperatures of electronically excited BiN radicals in a chemiluminescent flame

Rotational and vibrational temperatures of electronically excited BiN radicals in a low-pressure Bi_x+N/N₂*/N₂+Ar chemiluminescent flame have been deduced from high-resolution Fourier-transform emission spectra. Bands of three electronic transitions, a³Σ⁺(a₁1)→X¹Σ⁺(X0⁺), b⁵Σ⁺(b₁0⁺)→X¹Σ⁺(X0⁺), and b⁵Σ⁺(b₁0⁺)→a ³Σ⁺(a₁1), were analysed to determine the optical temperatures in the a³Σ⁺(a₁1) and b⁵Σ⁺(b₁0⁺) states. The rotational temperatures characterising the rotational populations in the a₁1, v=0 and 1 states were determined from the a₁→X, 0-2, 0-3, 0-4, 1-1, and 1-2 bands. The b₁→X, 0-8 and 0-11 bands, and the b₁→a₁, 0-0 bands served to determine the rotational temperature of the radicals in the b₁0⁺, v=0 state. The temperatures derived from the various bands and transitions were well consistent and the mean rotational temperature was determined to be 353±18 K, which is close to the translational temperature of the gas.Vibrational temperatures of the radicals in the a₁1 and b₁0⁺ states were derived from band intensities of the a₁→X and from the b₁→X as well as b₁→a₁ systems, respectively. The Franck-Condon factors needed were calculated with RKR potentials deduced from literature values of the rotational and vibrational constants in the three states involved. The a₁1 vibrational temperature (336±21 K) was close to the rotational temperature, while the b₁0⁺ vibrational temperature (438±36 K) differed, likely due to the previously observed perturbation of the b₁0⁺ state.     

Negative molecular ion formation and work function changes: Experimental results for CO and CO2 scattering from nickel (+potassium) surfaces

The scattering of CO⁺ and CO⁺₂ at grazing incidence from Ni(111)+K and clean Ni(111), Ni(110) surfaces produces CO, CO₂ and dissociated species. The observation of negative species O⁻ and CO⁻₂ is strongly dependent on the K coverage or work function of the surface. The dissociation of CO⁺ (CO) is weakly changed by the presence of K, whereas in the CO⁺₂ (CO₂) case dissociation via CO⁻₂ → CO + O⁻ is strongly increasing with K coverage.     

Modeling of N2+ first negative spectra excited by electron impact on N2

Previously published intensity formulas for the calculation of N₂⁺ first negative spectra excited by electron impact on N₂ given by Herzberg and Muntz are generalized and adapted to arbitrary N₂X vibrational temperatures. The formulation includes all the quantities necessary for detailed computer modeling. Despite the refinements, the rotational structure and band profiles generated by the different methods agree to within a few percent at both normal (300°K) and elevated (5000°K) rotational and vibrational temperatures. Discrepancies in published A-values are noted and a recalculated array is given.     

Interferometrische Bestimmung der Gastemperatur in der Stickstoffniederdruckentladung

A Michelson-interferometer in combination with a He-Ne-laser was used to determine the gas temperature in a nitrogen low pressure gas discharge. With this method the radial temperature profile could be measured to about 96% of the tube radius. Moreover rotational temperatures were measured with a 2 m-grating spectrograph from the spectrum of N₂- and N₂⁺-bands. In the range from 4 to 10 torr and 25 to 100 mA gas temperatures between 460 and 890 K were measured with the belonging rotational temperature from 620 to 1170 K. At pressures below 10 torr a difference of the rotational temperatures from the first negative and the second positive system was found. A qualitative consideration on the mechanism of the radial heat conductivity in the positive column was added.     

第三族金属氧化物离子对二氧化碳转化的红外光谱研究

本文利用红外光解离光谱研究了第三族金属氧化物离子对二氧化碳分子的转化机制. 研究表明,对于[ScO(CO₂)_n]⁺体系,在n≤4时,形成了溶剂化结构;在n=5时,形成了碳酸盐结构,实现了二氧化碳的转化. 对于[YO(CO₂)_n]⁺体系,需要4个二氧化碳分子就可以实现二氧化碳的转化. 而在[YO(CO₂)_n]⁺体系中,只发现了溶剂化结构,没有观察到碳酸盐结构. 理论计算表明,[YO(CO₂)_n]⁺体系拥有最小的溶剂化结构向碳酸盐结构转化能垒,[LaO(CO₂)_n]⁺体系拥有最大的溶剂化结构向碳酸盐结构转化能垒. 本文从分子水平揭示了不同金属氧化物离子对二氧化碳分子转化的影响规律.     

半导体的CO2激光退火和合金化

本文主要研究连续CO₂激光对半导体的照射效应。实验结果与理论分析说明,用连续CO₂激光照射可将半导体样片加热到所需的温度。与其它短波长的激光不同,波长为10.6μm的连续CO₂激光照射半导体有如下特点:CO₂激光是借助于自由载流子吸收与半导体耦合;样片在深度方向被均匀加热;激光背面照射可以增强退火效果。连续CO₂激光照射可以固相外延再生长的方式使As离子注入Si的损伤层退火恢复。在再生长的过程中注入的As离子进入替位,电激活率很高,而且不发生杂质再分布。将连续CO₂激光背面照射成功地应用于GaAsFET制备欧姆接触,既可避免激光正面照射对器件结构的破坏,又能得到比热退火为好的电学性能。 关键词：     

[Co(CO2)n]+团簇的红外解离光谱实验和理论研究

本文利用红外光解离光谱研究了一价钴阳离子与二氧化碳之间的相互作用. 通过密度泛函理论计算得到[Co(CO₂)_n]⁺团簇的几何结构,并且模拟了它们的振动光谱与实验数值进行比较. 研究结果表明,在[Co(CO₂)_n]⁺(n=2∽6)团簇中,钴阳离子通过电四极矩静电作用以端点结合的方式与二氧化碳中的氧原子结合在一起. 团簇的红外光谱都集中在二氧化碳反对称伸缩的波数附近,并且随着团簇尺寸的变化出现蓝移,最后把[Co(CO₂)_n]⁺的红外光解离光谱与稀有气体贴附的[Co(CO₂)_n]⁺-Ar的红外光解离光谱进行了比较.     

Theoretical study of the coadsorption of CO and O2 on doped cationic gold clusters MAun + (M = Ti, Fe, Au; n = 1, 6, 7)

We present a study based on first-principles calculations of the adsorption of CO on selected equilibrium configurations of MAu_nO₂ ⁺ (M = Ti, Fe; n = 1, 6, 7) complexes resulting from the adsorption of O₂ on doped cationic gold clusters MAu_n ⁺. Empirical rules for the formation of CO₂-MAu_nO⁺ complexes are outlined. The desorption energy of CO₂ is calculated. The adsorption of a second CO molecule on the residual MAu_nO⁺ complex leads in some cases to the formation of CO₂-MAu_n ⁺. The desorption of a second CO₂ molecule brings back to the initial doped gold cluster MAu_n ⁺.     

The Excitation Temperatures of Nonmetal Atoms and the OH Temperatures in Microwave-Induced Plasma

Abstract

The excitation temperatures of nonmetal atoms and the OH molecule temperatures have been measured in argon MIP, operating under atmospheric pressure at different experimental conditions. Atoms of Ar I, P I and H have been used as thermometric species. The rotational and vibrational temperatures have been obtained from the OH A²Σ⁺ - X²? band spectra. The ^SR₂₁ ratational lines have been used for the first time for the temperature measurements. The energy distributions observed here are discussed.     

The formation of excited CO2+ ions by vacuum ultraviolet radiation

Excited CO₂⁺ ions are formed by irradiating CO₂ molecules with the synchrotron radiation. The excitation function of CO₂⁺ (B?²Σ_u⁺) shows a pronounced structure which can be explained by an interaction of the Rydberg states npπ_u converging to C²Σ_g⁺ with the continuum of B?²Σ_u⁺.     

DC discharge experiment in an Ar/N2/CO2 ternary mixture: A laboratory simulation of the Martian ionosphere's plasma environment

A low-pressure DC plasma discharge sustained in a 1.6%Ar–2.7%N₂–95.3%CO₂ ternary mixture is studied. This plasma was generated in a total pressure range from 1.0 to 4.0 Torr, a power of 6.3 W and a 12 l/min flow rate of gases. The electron temperature was found to be 8.41 eV and the ion density, in the order of 10⁹ cm⁻³. The species observed in the plasma mixture were CO₂, CO₂⁺, CN, CO, CO⁺, O₂, O₂⁺, N₂, N₂⁺, NO, C⁺, Ar and Ar⁺. At the pressure range in the present study, the species observed do not change their intensity due to an increase in the pressure and they separate in two groups according to their emission intensity: the band of the first group (CO₂, CO₂⁺ and CN) is approximately a factor of 3 more intense than that of the second group (CO, CO⁺, O₂, O₂⁺, N₂, N₂⁺, NO, C⁺, Ar and Ar⁺). The behavior of the emission intensities may be correlated to the constant ion density and electron temperature measured. Also, we observed the same constant behavior in the ratios of the neutral and positive species intensities to that of the N₂ intensity, as a function of pressure. This may suggest that the different rate coefficients and cross sections of elastic collision, excitation and de-excitation of electronic or vibrational levels, inelastic and superelastic collisions of electrons with the gas phase and products, neutral–neutral interactions, resonant charged transfer processes, recombination, to mention some, to produce these species change in the same proportion, as a function of the pressure to keep the relative ratios of the species almost constant.     

Rotational analysis of the (3, 6) band in the comet-tail (AΠi -XΣ) system of CO

The direct observation and rotational analysis of the (3, 6) band in the comet-tail (A²Π_i-X²Σ⁺) system of CO⁺ are carried out for the first time employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. That 193 lines are assigned to this band ranging from 12 100 to 12 370 cm⁻¹ results in most accurate molecular constants by nonlinear least-squares fitting procedure employing the effective Hamiltonians.     

Radiative lifetimes and electronic quenching rate constants for single-photon-excited rotational levels of no (A2Σ+, ν′ = 0)

A narrow-band, frequency-doubled, tunable dye laser has been used to excite fluorescence from the A²Σ⁺, ν′ = 0 state of NO. Collision-free lifetimes were measured for 21 different K′ levels giving a mean radiative lifetime τ = 217 ± 4 ns. Electronic quenching rate constants of NO (A²Σ⁺, ν′ = 0) were measured for O₂, N₂, H₂O, CO₂ and Ar. No dependence of the quenching-rate constant on the initially excited rotational level was observed.     

NO excitation and thermal non-equilibrium within a flat plate boundary layer in an air plasma

Optical emission spectroscopy experiments are carried out by recording the radiation from the γ transitions of nitrogen monoxide in an air inductively coupled plasma in interaction with a water-cooled metallic flat plate at moderate pressure. The calibrated results allow to derive the vibrational and rotational temperatures of the NO(A ² Σ ⁺) excited state as well as its densities in the free jet and within the boundary layer by comparison with calculated spectra. Those results are compared with previous ones concerning temperatures and densities of the ground states of the majority species (N₂, O₂ and NO) that were obtained by laser techniques. As for the NO(X ² Π) ground state, vibration and rotation of the excited state are found out of equilibrium. The NO(A ² Σ ⁺) excited state is found to be populated by an energy transfer from the metastable N₂( A³\varSigma ⁺_uA^{3}\varSigma ^{+}_{u}). The steady state of the plasma allows using this property to derive N₂( A³\varSigma ⁺_uA^{3}\varSigma ^{+}_{u}) densities and N₂ electronic excitation temperatures. Close to the wall, a production of excited NO by a catalytic process is also considered involving N₂( A³\varSigma ⁺_uA^{3}\varSigma ^{+}_{u}) as source of adsorbed atoms. The present results confirm that the kinetic temperature cannot be compared to the rotational temperature derived from optical emission spectroscopy in such plasma conditions.     

Rotational dependence of Franck-Condon factors for OH+, NH+, SiH,MgH+, SiH+, and NO+

The rotational dependence of Franck-Condon factors has been calculated for OH⁺, NH⁺, SiH, MgH⁺, SiH⁺, and NO⁺ using the rotating Morse oscillator model. A rotational dependence is noticed in the electronic bands of each of these molecular species; this dependence may make a significant contribution in the determination of rotational temperatures, abundances and opacity distribution functions.     

The electron beam technique in carbon monoxide: Rotational transition probabilities

The electron beam fluorescence technique was developed to measure the rotational level population in the ground state of a carbon monoxide molecule. The data on rotational transition probabilities under ionization–excitation of CO (X¹Σ⁺) into the CO⁺ (B²Σ⁺) state by high energy electrons are presented, which noticeably differ from those predicted by the dipole excitation model. A flow in a free jet was used to obtain the experimental data in a low temperature rotationally equilibrium gas target. The probability matrix is represented in a compact form corresponding to the sudden approximation model.     

The behavior of nitrogen excited in an inductively coupled argon plasma

An inductively coupled argon plasma, working at atmospherique pressure, was used as an excitation source for nitrogen gas. Excitation of atomic lines of N and of molecular bands of N₂ and N⁺₂ were observed. Two lines (389.2 and 388.8 nm) which were not previously described, are attributed to atomic nitrogen. Using the first negative system of N⁺₂, several temperature-measurement methods were used according to the resolving power of the monochromator. Good agreement is found between the rotational (4500–5000 K) and excitation temperatures (4500–5100 K) of elements injected into the plasma.     

The Ethylene Hot Band Spectrum near 3000 cm

A new hot band spectrum of ethylene has been recorded from 2970 to 3015 cm⁻¹at low rotational temperatures in a seeded molecular jet, using vibrational energy transfer from SF₆to C₂H₄. An IR–IR double resonance technique has been applied to pump the lower states and subsequently probe the hot bands. Two new hot bands, ν₁₀+ ν₁₁− ν₁₀and ν₇+ ν₁₁− ν₇, have been found. The weak hot band starting from ν₇has been identified by direct labeling of some rotational levels in the ν₇manifold. High resolution FTIR spectra at ambient and at elevated temperatures have been recorded, too; it has thus become possible to extend the analysis to higher rotational quantum numbers. The previously analyzed ν₉+ ν₁₀level has been reinvestigated and ab-type Coriolis interaction with the nearby ν₇+ ν₁₁state has been observed. Rotational energy levels of ν₇+ ν₁₁and of ν₉+ ν₁₀have been fitted simultaneously, taking into account the local perturbations due to five dark states. From the shift of allK≠ 0 levels to higher frequencies in the ν₁₀+ ν₁₁state, a globala-type Coriolis interaction with ν₈+ 2ν₁₂has been identified.     

Molecular relaxations in mixtures of O2 with CO2 observed on?laser-induced gratings

Laser-induced gratings in mixtures of O₂ with CO₂ were formed by excitation of the O₂ molecules to the singlet state b ¹ Σ _g ⁺(v′=0). Density changes from heat release and from electrostriction, and variation of electric polarizability by excitation of molecules contribute to the grating. For modeling the relaxation of the excited O₂ molecules, a three-step process is assumed: Fast heat release with respect to the rotational states first, then medium fast electronic de-activation with excitation of vibrational states of the O₂ and CO₂ molecules, and then the final slow heat release processes. The observed temporal evolution of the diffraction efficiency of the grating agrees rather well with modeling. Average rates of the final relaxations and the value of the polarizability of the singlet state b ¹ Σ _g ⁺(v′=0) are determined in this way.     

Nuclear structure and direct reaction mechanism in neutron scattering on 28Si in the energy range 6.8 to 14.8 MeV

The structure of excited states in ²⁸Si as well as the energy dependence of the reaction mechanism are investigated. Angular distributions related to the 0₁⁺, 2₁⁺, 4₁⁺, 0₂⁺, 3₁⁺, 2₂⁺ + 2₃⁺, 3₁⁻ + 4₂⁺ levels in the ²⁸Si(n, n′) reaction were measured at incident energies 6.8, 7.0, 8.0 … 12.0 MeV. The analysis was extended up to 14.8 MeV bombarding energy. The experimental cross sections are described by means of a coupled-channel calculation including compound nucleus contributions. The low-lying excited states can be interpreted by a rotational model with prolate but also with oblate g.s. deformation. For the higher-lying states various coupling schemes have been tested. Especially, a second rotational band could be described adopting an oblate deformation.