Knowledge Bank

A high-sensitivity FT-IR spectrosmeter operating at the range of $6000-8000cm-1$ 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 $1.5cm-1$. The dependence of predissociation dynamics upon the different bound states of Ar-HF and $N2-HF$ are under further investigation. The intermolecular potential energy of $N2-HF$ was calculated using CCSD(T) method with Dunning's tripple-$\zeta$ basis function. With HF valence coordinate lying between 0.85 and $1.25\backslash AA$, 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 $D0$ is predicted to be $370cm-1$, in agreement with the experimental result of $398\pm 2cm-1.c$ Eighty-seven percent of vibrational redshift at VHF = 3 level is shown to occur as first order perturbation of the interaction potential.