QUANTUM MECHANICAL TREATMENT OF TWO INTERACTING RIGID ROTORS: APPLICATION TO $(HCl)_{2}$

Abstract

A simplified approach to the quantum mechanical description of two interacting rigid rotors is presented. The procedure is similar to that recently developed by $Clary^{1}$ with the intermolecular separation (R) being fixed at its equilibrium value. The potential energy surface is then described by the internal coordinates $\Theta_{1}$ and $\Theta_{2}$ between the HCl subunits and the intermolecular axis, and the torsional angle $\phi$. The rotational tunneling spectrum is predicted using an electrostatic intermolecular potential and is compared to the experimentally determined $(HCl)_{2}$ spectrum. Of particular interest are the relative Intensities of these tunneling transitions, which we have observed experimentally in combination with the HCl stretch. This technique can be applied to other rotor-rotor dimer systems such as $(HF)_{2}$ and $(HCCH)_{2}$