VIBRATIONAL PREDISSOCIATION DYNAMICS OF HF-COMPLEXES AT $v_{HF}=3$

Abstract

We report the lifetimes and rotational distributions of HF products from the vibrational predissociation (VP) of the ArHF and $Ar_{3}HF$ at $v_{HF}=3$ by dispersing laser induced fluorescence. The product state distribution of these two complexes has shown that the excess energy resulting from VP ($\Delta v = -1$) is partioned primarily into $HF(v = 2)$ product rotation. The distribution is extremely sharply peaked near the highest energetically accessible rotational channel $(J = 13$ for ArHF(3000) and $J^{\prime} = 12$ for $Ar_{3}HF$). The lifetimes of ArHF(3000) and (3110) states are found to be $4.8 \times 10^{-6}$ sec and $8.9 \times 10^{-6}$ sec respectively. Much shorter vibrational predissociation lifetime of 3 nsec is determined for $Ar_{3}HF$ at $v = 3$, revealed from the Lorentzian component of 60 MHz of the Voigt profile. The correlation of VP lifetime and red-shift for HF-complexes at $v = 3$ will be compared to that at $v = 1$. At the fundamental valence excitation ($v_{HF} = 1 \leftarrow 0)$, the VP rate varies as the square of the frequency $red-shift.^{a}$ At the present second overtone excitation $(v_{HF} = 3 \leftarrow 0)$, based upon $(HF){2}, N{2}HF$ and $Ar_{3}HF$ results, the VP rate varies more dramatically as the cube of the frequency red-shift. This suggests that a relatively complex model is required to fully account for the enhancement of VP rates observed for HF-complexes at $v = 3$.