15min:

ZHENHONG YU, PATRICK MEDLEY, BRENDAN CONNORS AND WILLIAM KLEMPERER, Harvard University, Department of Chemistry and Chemical Biology, Cambridge, Massachusetts 02138.

The binary complex between HF and HCl at _HF = 3 level, which has two stable forms: HF-HCl and HCl-HF, is studied recently by molecular beam laser induced fluorescence with an intracavity Ti-sapphire ring laser and the detection of HF = 2 0 emission. Similar to previously reported K = 0-0 (300000) (000000) transition of HF-HCl, 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 _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) (000000) combination transition of HCl-HF. The 2D vibration-averaged ab initio interaction potential of the complex predicts the HCl-HF form becomes more stable than HF-HCl through the valence excitation. The isotopic variation of predissociation lifetime for the observed transitions is still under investigation.