USE OF CORRECTED CENTRIFUGAL SUDDEN APPROXIMATIONS FOR THE CALCULATION OF EFFECTIVE CROSS-SECTIONS .2. THE N2-HE SYSTEM

A series of centrifugal sudden (CS) and infinite-order sudden (IOS) approximations together with their corrected versions, respectively, the corrected centrifugal sudden (CCS) and corrected infinite-order sudden (CIOS) approximations, originally introduced by McLenithan and Secrest [J. Chem. Phys. 80, 2480 (1987)], have been compared with the close-coupled (CC) method for the N2-He interaction. This extends previous work using the H2-He system [J. Chem. Phys. 93, 3931 (1990)] to an interaction which is more anisotropic and more classical in nature. A set of eleven energy dependent cross sections, including both relaxation and production types, has been calculated using the LF- and LA-labeling schemes for the CS approximation, as well as the KI-, KF-, KA-, and KM-labeling schemes for the IOS approximation. The latter scheme is defined as KM = K = max (k(j),k(jI)). Further, a number of temperature dependent cross sections formed from thermal averages of the above set have also been compared at 100 and 200 K. These comparisons have shown that the CS approximation produced accurate results for relaxation type cross sections regardless of the L-labeling scheme chosen, but inaccurate results for production type cross sections. Further, except for one particular cross section, the CCS approximation did not generally improve the accuracy of the CS results using either the LF- or LA-labeling schemes. The accuracy of the IOS results vary greatly between the cross sections with the most accurate values given by the KM-labeling scheme. The CIOS approximation generally increases the accuracy of the corresponding IOS results but does not completely eliminate the errors associated with them. For some cross sections, the CIOS results are more accurate than the corresponding CS or CCS results.