Rotational compound state resonances for an argon and methane scattering system

A broad compound state (closed channel) resonance in the argon--methane system is investigated using a realistic model potential, and approximations are developed which allow one to search for such resonances easily. Methane is treated as a rigid rotor and the energy of the resonance is such that there are only three rotational states with open channels. The coupled states approximation proved invaluable in characterizing the resonances. A perturbation technique was developed which allows one to predict accurately the position of the peaks due to the resonance. Fully converged close coupled differential and integral cross sections are presented