ClFx–H2 chemical lasers (x=1,3,5): vibration–rotation emission by HF from states with high rotational excitation

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Abstract
Stimulated vibration–rotation emission by HF has been observed from states with high rotational excitation following flash photolysis of ClFx–H2–Ar mixtures (ClF, ClF3, ClF5). We report here only those observations connected with the very high rotational states J′?9 (e.g., up to v=1, J=20 and v=2, J=15) which are found to emit under grating‐selective conditions. The patterns of emission indicate that direct population of the high J states by the vibrational pumping reaction(s) can be ruled out. Neither is the behavior consistent with Boltzman equilibration. The late threshold times and extended durations point to an energy transfer mechanism that involves rapid V→R deactivation with large ΔJ coupled with V→V up pumping in HF‡–HF‡ collisions to give a cumulative increase in rotational energy. Thus, V→V and V→R processes divert vibrational excitation into rotational excitation where it will tend to ’’pool’’ in high J states for which rotational equilibration is a slow process. These high J, P branch laser emissions reflect the role of rotational degrees of freedom in reaction dynamics and they furnish distinctive clues to energy processes that can influence significantly the efficiency and spectral composition of chemical laser emission.