Relaxation Of Carbon Monoxide Research Articles

Scaling laws for CO lasers

An analytic, quasisteady-state model for the description of vibrational relaxation in carbon monoxide is presented. It is shown that simple expressions result for the laser parameters as a function of vibrational energy loading, which is a particularly important variable in gas-flowing systems. Scaling laws are deduced and the model is compared with experimental results.

A study of the dynamic behavior of the vibrational population relaxation in carbon monoxide

The dynamic behavior of a relaxing CO–He mixture has been studied with a computer. The time evolution of the nonequilibrium vibrational population distribution was obtained by numerically integrating the master equations for the vibrational population including vibrational–vibrational (V–V), vibrational–translational (V–T), and spontaneous decay processes. The results show the characteristic relaxation through the V–V energy transfer of an anharmonic molecule. The calculations are compared with the vibrational population distribution measured from two different experimental works: (i) ir chemiluminescence data from chemically excited CO formed in the reactions O+C2H2 → CO*+CH2+51 kcal/mole, O+CH2 → CO*+2H+71 kcal/mole; (ii) vibrationally excited CO produced in an electrical discharge induced reaction O+CS2→SO+CS, O+CS→CO*+S+75 kcal/mole and measured using a pulsed delay technique.

The carbon monoxide laser. Population inversion mechanism

A review is given of the investigations of the mechanism of population inversion of vibrational levels in gas-discharge CO lasers operating at room and liquid nitrogen temperatures . Special attention is paid to the published theoretical and experimental information on the probabilities of vibrational transitions in molecules. Calculations of the populations of vibrational levels in the CO laser are discussed in detail. An analysis of these investigations demonstrates the correctness of the hypothesis postulating that the vibrational degrees of freedom of the CO molecule are pumped by electron impact and the higher levels are populated by the relaxation of carbon monoxide, which can be regarded as the relaxation of a system of anharmonic oscillators as first suggested by Treanor.

Shock-tube study of vibrational relaxation in carbon monoxide using pressure measurements

Measurements of pressure on the end wall of a shock tube have been used to infer the continuously varying rate of vibrational excitation behind incident shock waves in undiluted carbon monoxide. Results are presented in the form of separate relaxation-time plots for each shock wave studied. The data cover the temperature range 2400-6000°K and are in excellent agreement with the previous results of Matthews 1 and Hooker and Millikan.2 The relaxation-time curves from all the experimental runs tend to fall on a single straight line on a conventional Landau-Teller plot, with the exception of data obtained near equilibrium. These results support use of the Landau-Teller rate equation to describe vibrational excitation in CO for situations involving large departures from equilibrium, but point out the possible need to modify the rate equation for situations in which the vibrational energy mode is highly excited.

Anharmonicity effect on vibrational relaxation in carbon monoxide

Abstract A previous modelfor calculating the cross of the vibrational excitation of carbon monoxide by collision with carbon monoxide has been improved to include anharmonicity effects in the vibrational wavefunctions by describing them in terms of Morse oscilaltors. It is shown that this leads to further improvement in the agreement between the theoretical and experimental values for the vibrational relaxation times The sensitivity of the total cross sections to anhramonicity is investigated at several collision energies and further lines of approach are suggested.

A recalculation of vibrational excitation in carbon monoxide

A previous calculation of the cross sections for the vibrational excitation of carbon monoxide by collision with carbon monoxide made by Marriott in 1964, has been repeated with allowance for the effect of the repulsive centrifugal potential term on the matrix transition elements. It is shown that this leads to improved agreement between the theoretical and experimental values for vibrational relaxation in carbon monoxide. The sensitivity of the cross sections to variations in the empirical potential parameters is also investigated.

Molecular collision cross sections and vibrational relaxation in carbon monoxide

A method for the calculation of cross sections for processes involving the exchange of vibrational and translational energy on collision of molecules with internally structureless particles is described. On the assumption that the excited molecule is a simple harmonic vibrator and that the molecular interaction potential may be represented by a spherically symmetric Lennard-Jones function, the partial wave scattering equations have been obtained in a form suitable for direct numerical integration. Coupling between any selected number of energetically accessible molecular vibrational states can be retained in this calculation. The collision cross sections are then derived in terms of the asymptotic phases and the amplitudes of the numerical solutions.

Shock-Tube Study of Vibrational Relaxation in Carbon Monoxide for the Fundamental and First Overtone

The rate of vibrational excitation in rapidly heated CO has been determined for the temperature range 1100°—2500°K by observation of infrared emission behind incident shocks. Great care was taken to eliminate impurity effects. The data agree to within 15% with those of Matthews. Separate observations of fundamental and overtone emission demonstrated that excitation occurs in a stepwise fashion. Collisional population of the v=2 level by successive single quantum transition is at least ten times faster than the direct 0→2 excitation process. Vibrational relaxation times of CO were determined for the pure gas and for the mixtures; 5% CO—95% Ar, 5% CO—95% N2, and 99% CO—1% H2. At 2000°K, τ(CO–CO) = 60 μsec, τ(CO–Ar) = 350 μsec, τ(CO–N2) = 640 μsec, τ(CO–H2) = 0.7 μsec, all for one atmosphere total pressure with the CO infinitely dilute in the second-named gas. The differences found between CO–CO collisions and CO–N2 collisions with respect to vibrational excitation are not explained by current theories.

Vibrational Relaxation in Carbon Monoxide by the Spectrophone Frequency-Response Method

Although the spectrophone has been employed earlier to measure vibrational relaxation times by a phase-shift method, the use of a frequency-response (amplitude) method does not seem to have been previously reported. The limitations of microphone response to audio frequencies precludes the investigation of most gases by this procedure, but the expected long relaxation time in carbon monoxide suggested that a response loss might be observable for this molecule. After some difficulties due to acoustic resonances in the spectrophone cell were overcome, a relaxation loss (relative to CO2) was found at room temperature for carbon monoxide, which corresponds to a relaxation time of approximately 2 msec at 1 atm. The result is compared with values found at much higher temperature by shock-tube experiments. While the result for τ appears to be somewhat low in comparison with the shock-tube results, which may be due to traces of H2O or of H2 in the sample, the method appears to be useful in extending the range of measurements beyond that previously available by other techniques.

A study of vibrational relaxation in carbon monoxide by shock waves and infra-red emission

A study of vibrational relaxation in carbon monoxide by shock waves and infra-red emission