Model calculations on the ground vibrational state of Ar–HCN

Publisher Website
Google Scholar
Abstract
The Ar–HCN complex exhibits unusually wide amplitude bending along with large isotope and centrifugal distortion effects. A model in which Ar–HCN tunnels between linear and T‐shaped configurations is able to quantitatively account for most of these experimental observations. A parametrized model potential is used and solutions are obtained variationally using a form for the wave function which is arbitrary in the bending angle but Gaussian in the stretching coordinate. The accuracy of the variational solution is checked against results from a two dimensional numerical relaxation procedure. In the final potential, the center of mass separation is about 4.62 Å in the linear, global minimum and 0.86 Å less at the T‐shaped configuration. The potential is such that, in the ground vibrational state, the T‐shaped region is not classically allowed but the wave function penetrates significantly into this region. This tunneling is the origin of the large isotope effects. The combination of the tunneling with contraction in bond length between the linear and T‐shaped structures leads to the large centrifugal effects.