VIBRATIONAL PREDISSOCIATION OF THE HF-HC1 COMPLEXES AT $\nu_{HF} = 3$ LEVEL

$^{a}$H. -C. Chang and W. Klemperer, J. Chem. Phys. 98, 2497(1993). $^{b}$R. Mollaaghababa, H. -C. Chang and W. Klemperer, Can. J. Phys. 72, 963(1993). $^{c}$G. T. Fraser and A. S. Pine, J. Chem. Phys. 91, 637(1989).Author Institution: Department of Chemistry and Chemical Biology, Harvard UniversityThe binary complex between HF and HC1 at $\nu_{HF} = 3$ level, which has two stable forms: HF-HC1 and HC1-HF, is studied recently by molecular beam laser induced fluorescence with an intracavity Ti-sapphire ring $laser^{a}$ and the detection of HF $\Delta\nu = 2 \leftarrow 0$ emission. Similar to previously reported $K = 0-0 (300000) \leftarrow (000000)$ transition of $HF-HC1^{b}$, the $K = 1-0$ subband seen at $11353.2 cm^{-1}$ shows significant rotational dependence to the predissociation linewidths, varying from 1.3 to 2.4 GHz. The rotational A constant of $43.5 cm^{-1}$ clearly indicates that the vibration-averaged angle between the HF axis and a-axis decreases over valence excitation, compared to $40.1 cm^{-1}$ at $\nu_{HF} = 1$ level. Another weaker Q-branch band observed at $11351.7 cm^{-1}$, with slightly narrower linewidths and little apparent J dependence, is tentatively assigned to the $K = 1-0 (301000) \leftarrow (000000)$ combination transition of HC1-HF. The 2D vibration-averaged ab initio interaction potential of the complex predicts the HC1-HF form becomes more stable than HF-HC1 through the valence excitation. The isotopic $variation^{c}$ of predissociation lifetime for the observed transitions is still under investigation