Effect of longitudinal flow velocity on the emission spectrum of CO2 lasers

Experimental evidence was presented demonstrating the significant role of the longitudinal velocity flow of the lasing molecules in determining the rotational spectrum of the CO2 laser emission. The contribution arising from filling or nonfilling of the spatial holes in the inverted population became less crucial if the stimulated emission rate surpassed the rotational relaxation rate, as then a rotational hole will be burnt in the Boltzmann population distribution. This was indeed the situation for very high-gain CO2 lasers which usually show multiline oscillations.