QUANTUM-MECHANICAL CALCULATIONS OF EFFECTIVE COLLISION CROSS-SECTIONS FOR HE-N2 INTERACTION .1. VISCOMAGNETIC EFFECT

For the He-N2 system quantum mechanical calculations of the effective cross-sections that govern both the viscomagnetic effect and the collision broadening of the depolarized Rayleigh (DPR) line in mixtures have been performed. The results provide a set of 'benchmark' cross-sections for atom-heavy rigid rotor systems interacting through a realistic anisotropic intermolecular potential. In addition, comparisons have been made with equivalent calculations using the classical trajectory approach. The accuracy of the classical calculations has been tested, both at the macroscopic level in the temperature range from 70 K to 500 K and at an intermediate level as a function of the total energy. The results indicate that the classical trajectory calculations are in good agreement with the present quantal calculations. For all cross-sections the difference between classical and quantal results becomes progressively smaller with increase in total energy or temperature. This indicates that a hybrid scheme, which employs classical trajectory, results at high energy and quantal results at low energy, is an accurate and computationally sensible method of studying the effective cross-sections that govern the viscomagnetic effect in polyatomic gases.