Dissociation mechanism in pulsed and continuous CO2 lasers

Abstract

The dissociation of carbon dioxide in the positive column of a glow discharge has been measured in CO2 and in CO2-N2 and CO2-N2-He mixtures as used in low-pressure (1-20 Torr) gas lasers. Both for continuous and pulsed discharges the measured dissociation rate is proportional to the electron density. The dissociation coefficient increases with the reduced field strength E/p, but for a given E/p it is very much greater for CO2-N2-He than for CO2-N2, and is greater for CO2-N2 than for CO2. This variation is consistent with the variation of the electron energy distribution and drift velocity with the different gases, and it is not necessary to postulate more than one dissociation mechanism.

Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas

“…The electron energy dependence of this cross section is in satisfactory agreement with the indirect measurements performed by Corvin and Corrigan, with a threshold energy of 6.1 eV and a peak of 0.35 × 10 –16 cm 2 at 6.9 eV. Similar measurements performed by Smith and Austin validated the results of Corvin and Corrigan …”

A sealed high-repetition-rate TEA CO2laser

“…According to Smith and Austin [9], the dissociation of CO., in He-N , -CO ., gas mixtures is due to single-electron impact processes. Using this fact , Smith [22] has calculated that the dissociation coefficient is given by:…”

Spectroscopic Study of CO2 Decomposition in Sealed-off CO2 Lasers

“…The early works of Smith and Austin [21] show that the prevailing CO 2 dissociation reaction in a CO 2 laser discharge is neutral dissociation by electron impact:…”

“…Several authors [e.g. 15,16,21,23] have found that the CO 2 equilibrium conversion into CO increases with decreasing pressure and increasing discharge current. A detailed theoretical study of different CO 2 laser mixtures by Cenian et al [17,22] made clear that the pressure dependence of the CO 2 conversion is linked to the pressure dependence of the reduced electrical field strength.…”