VIBRATIONAL PREDISSOCIATION OF AN INERT-GAS CLUSTER CONTAINING AN ACTIVE-MOLECULE - THE UPSILON(HF)=3 SPECTRUM OF AR3HF

The upsilon(HF)=3<--0 HF valence excitation spectrum of Ar3HF is obtai ned by intracavity laser induced fluorescence. The spectroscopic const ants determined for the upsilon(HF)=3 level are band origin nu(0) 11 3 10.4520(4) cm(-1) (corresponding to the vibrational redshift of Delta nu = -62.355 cm(-1)), the constants B=0.039 743(5) cm(-1) and D-J=2.04 (12)x10(-7) cm(-1). The changes in constants upon HF valence excitatio n to upsilon=3 are Delta B=1.08(5)x10(-4) cm(-1) and Delta C=1.01(6)x1 0(-4) cm(-1). The increase in C is interpreted as the occurrence of a 0.2% decrease in the Ar-Ar separation. Appreciable line broadening is observed in the Ar3HF(upsilon=3) spectrum. Twenty-three Lines in P and Ii branches are fitted by the Voigt profile with 60 (10) MHz Lorentzi an component establishing the occurrence of significant vibrational pr edissociation for Ar3HF at upsilon(HF)=3 This rate is consistent with the empirical scaling of the vibrational predissociation rate with the frequency redshift, observed fur stronger hydrogen bonded complexes o f I-if. The scaling of the vibrational predissociation rate for ArnHF (n = 1-3) with the argon number, n, is poorly defined. (C) 1998 Americ an Institute of Physics.