VIBRATIONAL PREDISSOCIATION OF WEAKLY BONDED HF COMPLEXES: AN EXPERIMENTAL STUDY WITH FT-IR SPECTROSCOPY
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Date
2003
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Publisher
Ohio State University
Abstract
A high-sensitivity FT-IR spectrosmeter operating at the range of $6000-8000 cm^{-1}$ was assembled by using a liquid nitrogen-cooled germanium detector and a home-made Michelson interferometer. The valence excitation of HF containing species is carried out with a 40W intracavity Ti-sapphire ring $laser.^{a}$ With the detection of HF $\nu = 2 \leftarrow 0$ emission, this method is suitable for analyzing the product distribution for vibrational predissociation of hydrogen bonded HF complexes. The rotational distribution of product HF can be easily measured with our spectral resolution of $1.5 cm^{-1}$. The dependence of predissociation dynamics upon the different bound states of Ar-HF and $N_{2}-HF$ are under further investigation. The intermolecular potential energy of $N_{2}-HF$ was calculated using CCSD(T) method with Dunning's tripple-$\zeta$ basis function. With HF valence coordinate lying between 0.85 and $1.25\AA$, the calculation of vibration-averaged interaction potential was achieved perturbatively through second order using Herman's analytic $wavefunction.^{b}$ The vibrational frequncies of intermolecular modes was determined through further adiabatic approximation. the dissociation energy $D_{0}$ is predicted to be $370 cm^{-1}$, in agreement with the experimental result of $398\pm2 cm^{-1}.^{c}$ Eighty-seven percent of vibrational redshift at VHF = 3 level is shown to occur as first order perturbation of the interaction potential.
Description
$^{a}$H. -C. Chang and William Klemperer, J. Chem. Phys. 98, 2497(1993). $^{b}$R. M. Herman, R. H. Tipping, and S. Short, J. Chem. Phys. 53, 595(1970). $^{c}$R. J. Bemish, E. J. Bohac, M. Wu, and R. E. Miller, J. Chem. Phys. 101, 9457(1994).
Author Institution: Department of Chemistry and Chemical Biology, Harvard University
Author Institution: Department of Chemistry and Chemical Biology, Harvard University