THE STRUCTURAL DEPENDANCE OF HF VIBRATIONAL RED SHIFTS IN $Ar_{n}HF$ CLUSTERS VIA HIGH RESOLUTION INFRARED SPECTROSCOPY

Author Institution: Joint Institute for Laboratory Astrophysics, University of Colorado, and National Institute of Standards and Technology, and the Department of Chemistry and Biochemistry, University of ColoradoThe rotationally resolved HF stretching spectra of $Ar_{n}F. n-1-4$, have been observed using a slit jet, difference frequency infrared laser spectrometer. The red shift of the HF vibrational frequency is shown to be sensitively dependent on the placement of the Ar with respect to the HF dipole moment: the largest incremental red shift is observed for the linear ArHF. The n-1-3 red shifts rapidly approach the values observed in an Ar matrix suggesting that only the nearest neighbors contribute significantly to the perturbation of the HF vibrational frequency. The observed $Ar_{4}HF$ isomer places the fourth Ar in what would be the second layer from the HF and has little effect on the observed red shift. This supports the importance of the nearest neighbors in determining the HF vibrational frequency. In all spectra, no evidence for vibrational predissociation is observed, indicating an extremely long lived HF vibration within the cluste