<title>Performance of CO2 and CO diffusively cooled rf-excited strip-line lasers with different electrode materials and gas composition</title>

Abstract

Strip-line molecular lasers with a narrow gas sheath confined by bare metal electrodes are sensitive to chemical processes that influence the gas composition during the RF discharge. Both CO2 and CO gas mixtures in a stationary gas in the discharge reach a steady state composition, and an associated asymptotic laser performance is attained. However, the process of CO2 dissociation has the opposite effect on the gas composition than CO + O recombination or 2CO ?CO2 + C disproportionation reaction. Therefore, materials like gold, that catalyze the CO2 formation, exhibit complementary behavior with respect to power decline in sealed off CO2 versus CO laser operations. We describe the operation of a RF excited strip-line CO gas laser at a cooling temperature of 0°C. The laser power and efficiency are critically dependent on the purity of the constituent gases and on the nature of the electrode metal. Changes in the laser power and efficiency during the discharge are correlated with measurements of changes in the gas constitution monitored mass spectrometrically. A solid powder (definitely not carbon soot) which has a deleterious effect on the laser performance was observed. Following Bhaumik et al, mercury vapor was introduced into the gas mixture in a conventional DC excited Pyrex tube. An improvement of better than 40% in the power and efficiency as well as changes in the spectral distribution of a CO laser were observed.