Detailed characteristics of a pulsed H_2 + F_2 laser 2: Theory

Abstract

A theoretical investigation of a pulsed, flash photolytically initiated, HF laser pumped by the H2 + F2 chain reaction is presented. The results of computer simulations of the laser kinetic mechanisms are compared to small signal gain, total pulse energy, and time-resolved spectral measurements. These comparisons show that a model assuming vibrational-to-translational (V–T) energy transfer as the dominant HF deactivation channel more closely predicts gain and spectroscopic durations, initiation, peak and termination times, plus peak gain magnitudes and total pulse energies than a similar model assuming vibrational-to-rotational (V–R) energy transfer as the dominant deactivation channel. This is contrary to the current understanding of HF kinetic mechanisms. It is concluded that the current understanding of these mechanisms is not sufficient to quantitatively predict either the time-resolved spectra or gain of the H2 + F2 laser. Model results also indicate that rotational relaxation is fast compared to other deactivation processes, but slow compared to stimulated emission. Finally, the model gives an estimated lower bound for the experimental [F]/[F2] ratio of 0.0025%.