Vibrational predissociation of an inert gas cluster containing an active molecule:: The υHF=3 spectrum of Ar3HF

The upsilon(HF)=3<--0 HF valence excitation spectrum of Ar3HF is obtained by intracavity laser induced fluorescence. The spectroscopic constants determined for the upsilon(HF)=3 level are band origin nu(0) 11 310.4520(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 excitation to upsilon=3 are Delta B=1.08(5)x10(-4) cm(-1) and Delta C=1.01(6)x10(-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 Lorentzian component establishing the occurrence of significant vibrational predissociation 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 of I-if. The scaling of the vibrational predissociation rate for ArnHF (n = 1-3) with the argon number, n, is poorly defined. (C) 1998 American Institute of Physics.