Vibrational Kinetics Research Articles

Analytical methods of solution of the relaxational equations

The master equations system for rotational, vibrational and chemical kinetics in nonuniform gas flows with the sources is studied. Two approximate analytical methods of its solution for the arbitrary rate constants are developed for the case of the smooth distributions. The first method is based on the introduction of slow variables to the discrete equations. The second one uses WKB solution for diffusion approximation in Fokker-Planck form. The particular cases of harmonic and weakly anharmonic oscillators relaxation are examined.

Vibration-to-translation energy exchanges in H2 colliding with highly vibrationally excited H2 molecules

Rate constants Kν,ν−1ν,ν for vibrational deactivation of H2 in highly excited vibrational states have been calculated using a semiclassical dynamical model. The results show a strong increase of K1,00,0 as well as Kν,ν−1ν,ν as a function of the vibrational quantum number ν. The dependence of K1,0ν,ν on ν could open new perspectives in non-equilibrium vibrational kinetics of H2.

Investigation of the energy parameters of the active medium of electric-discharge closed-cycle CO2lasers by the method absorption and emission of CO2in the 4.3 μm range

The absorption and emission of the CO2 molecule in the 4.3 μm range was used to study experimentally the dependences of the specific stored vibrational energy, the specific output energy, the maximum output power, and the gain on the input energy, pressure, and CO2 concentration in an N2–He–CO2–O2 mixture excited by a self-sustained glow discharge. The distribution of these parameters over the length of the discharge chamber of a continuous-flow commercial CO2 laser was also studied. A comparison was made between experimental values of the vibrational and translational temperatures and theoretical values determined from the gasdynamic and vibrational kinetics equations using measured electrical characteristics of the discharge. The influence of the unexcited layers of the active mixture on the parameters of the active medium was investigated.

Generalized relaxation equations for vibrational and rotational molecular kinetics in gas flows

Generalized relaxation equations for vibrational and rotational molecular kinetics in gas flows

Progress in the non-equilibrium vibrational kinetics of hydrogen in magnetic multicusp H − ion sources

The non-equilibrium vibrational kinetics of H 2 in multicusp magnetic discharges has been studied by improving a previous model developed by our groups. In particular, a complete set of V-T (vibrational translation) rates involving H-H 2( v) collisions, calculated by using a three-dimensional dynamics approach, has been inserted into our self-consistent model for better representing the corresponding relaxation. Different experimental situations are simulated with special emphasis on the temporal scales necessary for the different distributions (electron energy and vibrational distributions) to reach stationary values. Finally, a comparison between theoretical and experimental quantities such as vibrational temperature, electron temperature, electron number density and concentration of negative ions (H −) shows a satisfactory agreement, thus indicating the basic correctness of our model.

Multifrequency laser utilizing vibrational-rotational transitions in CO and CO2molecules excited by a non-self-sustained discharge

Experimental and theoretical investigations were made of the characteristics of an uncooled electron-beam-controlled atmospheric-pressure laser utilizing simultaneously vibrational–rotational transitions in the CO and CO2 molecules. A theoretical model was developed on the basis of a self-consistent solution of the equations of vibrational kinetics and the Boltzmann equation for the electron energy distribution function. A good agreement between the experimental and calculated results was obtained. An investigation was made of the problem of control of the emission spectrum. It was found theoretically that the overall efficiency could reach ~20% (in the case of approximately the same efficiencies in the spectral ranges 5.5 and 10.6 µ) if a laser of this type were cooled to 200 K.

Non-equilibrium vibrational kinetics of CO pumped by vibrationally excited nitrogen molecules: General theoretical considerations

The non-equilibrium vibrational kinetics of CO pumped by vibrationally excited N2 has been calculated by solving the vibrational master equations for both N2 and CO molecules, linked by V-V (N2CO) energy exchange processes. The results have been obtained for different values of the parameters governing the kinetics (in particular gas temperature, initial vibrational content of N2, different mixing ratios N2/CO). Emphasis is also given to dissipative channels present in CO, due to bimolecular reactions involving highly vibrationally excited CO molecules. The results shows the essential features of the temporal evolution of CO and N2 vibrational distribution as well as the strong coupling existing between them.

Non-equilibrium vibrational kinetics of CO pumped by vibrationally excited nitrogen molecules: A comparison between theory and experiment

Temporal evolution of CO vibrational distribution pumped by vibrationally excited nitrogen molecules has been experimentally determined by side-on infrared emission spectroscopy. Cooled and uncooled radiofrequency N2 discharges have been utilized to pump vibrational energy in N2, which then does excite CO in the post-discharge regime. CO2 formed during the contact time has been detected by a mass-spectrometric technique. The experimental results show the different stages of the relaxation of CO, merely the pumping, the redistribution and the loss of vibrational quanta introduced by N2. The results have been rationalized by means of a theoretical model which qualitatively reproduces the experimental relaxation of CO distributions as well as the production of CO2.

Propagation of an intensity-modulated laser beam through a pulsed CO2amplifier

A theoretical study was made (by a self-consistent solution of the equations of vibrational kinetics, hydrodynamics, and quasioptics) of the influence of self-interaction of laser radiation on the transmission of a beam through a CO2 amplifier. It was found that for times exceeding the time for collisional decay of the upper active level the radiation wavefront becomes unstable in the presence of small-scale perturbations of the transverse structure of the beam. It was shown that the harmful influence of the self-interaction on the divergence can be weakened by raising the intensity of the incident beam and the gain of the amplifier.

Nonequilibrium Vibrational Kinetics. Edited by M. Capitelli, University of Bari, Italy (Topics in Current Physics, Vol. 39, Springer‐Verlag 1986, 344 pp., 120 figs.)

Beiträge aus der PlasmaphysikVolume 27, Issue 4 p. 282-282 Book Review Nonequilibrium Vibrational Kinetics. Edited by M. Capitelli, University of Bari, Italy (Topics in Current Physics, Vol. 39, Springer-Verlag 1986, 344 pp., 120 figs.) R. Winkler, R. Winkler GreifswaldSearch for more papers by this author R. Winkler, R. Winkler GreifswaldSearch for more papers by this author First published: 1987 https://doi.org/10.1002/ctpp.19870270403AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume27, Issue41987Pages 282-282 RelatedInformation

Effect of vibrational kinetics of He2 + ions on the afterglow of a discharge in helium

A decaying weakly ionized helium plasma [ne=(0.2–1.1)·1011 cm−3, p=(40–70) mm Hg] was studied experimentally. It is shown that the experimental time dependences of the intensities of atomic lines and molecular bands in the afterglow phase can be explained if the vibrational kinetics of He2 + ions is included in the analysis. Analysis of the measurements shows that for ne ≲ 1011 cm−3 and Na ≳ 1018 cm−3 deexcitation of He2 + ions occurs primarily as a result of inelastic collisions with helium atoms. Based on the experimental data, an approximate value was obtained for the rate constants of the vibrational relaxation of molecular helium ions ≈10−16 cm3/sec. These results are used for making a qualitative analysis of the distribution of He2 + ions over the vibrational states in the discharge phase.

Refraction of laser radiation by self-interaction waves in CO2lasers

Numerical modeling method and simultaneous solution of the equations describing vibrational kinetics, hydrodynamics, and laser kinetics are used to study refraction of laser radiation by boundary thermal self-interaction waves in a pulsed electron-beam-controlled CO2 laser with a telescopic resonator. An analysis is made of the influence of this refraction on the deterioration of the divergence of laser radiation as a function of such parameters as an increase in the resonator length, pulse duration, and composition of the mixture. A calculation is made of the optimal values of the parameters for which the energy emitted in a given solid angle has its maximum value.

Nonequilibrium dissociation of diatomic molecules in flows with convective and diffusive particle transport

The nonequilibrium effects in the kinetics of the thermal dissociation which occurs in a streaming gas of diatomic molecules are investigated. Expressions are obtained for the macroscopic reaction rate and the vibrational energy distribution of the molecules, taking into account the influence of the gas motion. Cases of flows with convective and diffusive particle transport are considered. The dissociating molecules are simulated by cutoff harmonic oscillators. The vibrational kinetics is described in the framework of the so-called diffusion approximation.

Quasiequilibrium model of the kinetics of coupled modes of CO2 molecules

The correct allowance for the influence of anharmonicity in the vibrational spectrum of CO2 on the level distribution of molecules under nonequilibrium conditions, when the vibrational temperature departs significantly from the gas temperature, has become especially urgent in connection with obtaining generation on a number of long-wavelength transitions of CO2 molecules [1, 2]. The shifts in the levels of coupled modes (symmetric and deformation) are due mainly to Fermi resonance and can reach a considerable value, comparable with the gas temperature even for low levels. In [3] the main features of the quasisteady level distribution of coupled modes were clarified within the framework of the Treanor model of vibrational kinetics. The influence of the ascending flux of quanta, excited by VV exchange under nonequilibrium conditions, on the vibrational distribution was considered in [4–6]. In the present paper we propose a quasiequilibrium model of CO2 kinetics, obtained without presuming quasisteadiness of the ascending flux of quanta, and making it possible, in contrast to [3–6] to describe the dynamics of the variation of the distribution of molecules among multiplets as a result of processes of VV exchange and VT relaxation between multiplets, with allowance for possible processes of pumping by outside sources. With a Boltzmann population distribution within the multiplets, having the translational temperature of the gas, the problem of studying relaxation in coupled modes is reduced to the equations for an effective anharmonic oscillator with levels corresponding to the multiplets of CO2 molecules. In this case the levels of the effective oscillator are degenerate with a multiplicity equal to the number of levels in the corresponding multiplet, and they have an anharmonicity constant dependent on the gas temperature. The population distribution of the effective oscillator can be studied by methods developed for the investigation cf a one-mode anharmonic oscillator. The proposed quasiequilibrium model was used for a numerical calculations of the temporal evolution of the distribution function of CO2 molecules over the levels of coupled modes under the conditions of an extremely maintained discharge.

Gear's method in vibrational kinetics

Gear's predictor-corrector multistep method is applied to a rigid system of nonlinear ordinary differential equations, describing vibrational kinetic processes in molecular (diatomic) gas. The applicability of Naidis's formulas, for the linear problem is studied. The evolution of the starting Boltzmann distribution to the quasiequilibrium Trinor distribution is studied. The vibrational relaxation curves are calculated taking into account VV and VT processes and the possibilities of a more complicated starting physical model are examined.

Vibrational and chemical kinetics equations in a complex gas mixture

This paper presents simplifying assumptions used in formulating the kinetic equations: the chemical reactions do not spoil the Maxwell distribution; the rotational degrees of freedom are in equilibrium with the translational; each kind of vibrations mode of the molecules considered macroscopically is modeled by a harmonic oscillator with infinitesimal characteristic time of VV-exchange within the mode, and the vibrational temperature T /sub k/ is used as a measure of the mean energy of such mode; and the molecules of the components considered microscopically are modeled by Morse oscillators.

Investigation of the oxidation of carbon disulfide in gas flows using ir spectroscopy

The oxidation of carbon disulfide has been intensively studied recently because the carbon monoxide molecules formed during the chemical reaction have a large amount of vibrational energy and can be used to create laser media. Previously, studies have been made of the IR emission from a carbon disulfide flame and the dependence of the intensoty of emission from CO and CO/sub 2/ molecules on the stoichiometric ratio between the oxide and fuel concentrations has been found. In this paper the authors present the results from a spectroscopic study of the emission from a flame in the near infrared. The purpose of this work is to compare the spectra of carbon disulfide flames in different mixtures as well as to find the dependence of their shape on the pressure of the medium for a more detailed study of the effect of chemical and vibrational kinetics on the emission from CO molecules.

Vibrational kinetics of alkylperoxy radical destruction in pulse photolysis of the cyclohexane-O2 system

Vibrational kinetics of alkylperoxy radical destruction in pulse photolysis of the cyclohexane-O2 system

Vibrational kinetics of N-decane sulfoxidation at high pressure

Vibrational kinetics of N-decane sulfoxidation at high pressure

Structure and dynamics of excited singlet states of isolated diphenylhexatriene

The fluorescence spectrum, one photon fluorescence excitation spectrum, and single vibrational level decay kinetics have been measured for 1,6-diphenyl-1,3,5-hexatriene seeded in helium in a supersonic free jet. The 2 1Ag doubly excited state (S1) is located more than 3400 cm−1 below the strongly absorbing 1 1Bu state (S2) which is 29 157 cm−1 above the ground state. The lowest energy observed vibronic band of S1 is at 25 741.8 cm−1; emission produced by excitation into this band has a lifetime of 90.7 ns. The vibronic development of the excitation spectrum shows that this band is a vibronically promoted false origin. Fluorescence excitation intensity for this band is smaller than that of the S0 to S2 fluorescence excitation origin by at least a factor of 104. Direct excitation of S2 in the isolated molcule is followed by relaxation, fast on the nanosecond time scale, to isoenergetic vibrationally excited levels of S1. This is apparent both from the observed fluorescence spectrum and the fluorescence decay time (48.1 ns at the S2 origin) which is more than an order of magnitude longer than the intrinsic fluorescence lifetime of S2.