Body frame close coupling wave packet approach to gas phase atom–rigid rotor inelastic collisions

Abstract

The close coupling wave packet (CCWP) method is formulated in a body-fixed representation for atom–rigid rotor inelastic scattering. For total J>jmax the computational cost of propagating the coupled channel wave packets in the body frame scales approximately as N3/2 where N is the total number of channels. For large numbers of channels, this will be much more efficient than the space frame CCWP method previously developed which scales approximately as N2 under the same conditions. Timing results are reported for a model system for 25, 64, 144, 256, and 969 channels. The calculations were run with total J=30 and with parameters corresponding to a heavy diatom. The results for some representative transitions are compared to the identical transitions obtained using the space frame formalism. For all values of N, the body frame computations ran faster than the corresponding ones using the space frame, with the ratio increasing to a value of 4.5 for 969 channels. This is a significant improvement which will continue to increase with N, encouraging us to believe that the body frame CCWP method will prove practical for calculating scattering information for more realistic inelastic and reactive systems.