The influence of vibrational-relaxation on the operation of the 119 micron CH3OH laser

Measurements of the pressure dependence of the relaxation rate of vibrationally excited molecules in the 119 mum CH3OH laser have been correlated with the pressure and pump power dependence of the output power in the framework of a rate-equation model for which numerical and approximate analytical solutions have been obtained. Both diffusion and collisional de-excitation are important, and substantial deviations from thermal equilibrium populations are deduced, consistent with an operating pressure range which increases with pump power.