15min:

CHENG-CHI CHUANG, SUSY N. TSANG, KELLY HIGGINS AND WILLIAM KLEMPERER, Department of Chemistry, Harvard University, Cambridge, MA 02138; HUAN-CHENG CHANG, Institute of Atomic and Molecular Sciences, Academica Sinica, P.O.Box 23-166, Taipei, Taiwan 10764, Republic of China.

We report the lifetimes and rotational distributions of HF products from the vibrational predissociation (VP) of the ArHF and Ar₃HF 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 ( 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^'=12 for Ar₃HF). The lifetimes of ArHF(3000) and (3110) states are found to be 4.8×10^-6 sec and 8.9×10^-6 sec respectively. Much shorter vibrational predissociation lifetime of 3 nsec is determined for Ar₃HF 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 <- 0), the VP rate varies as the square of the frequency red-shift. At the present second overtone excitation (v_HF=3 <- 0), based upon (HF)₂, N₂HF and Ar₃HF 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.

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