Line shape in collision-induced absorption spectra: Theory and computer simulation for atomic and simple molecular species

A new and improved method is presented for computer simulation of collision-induced far-infrared absorption spectra of atomic and molecular species. The improvements involve (a) eliminating redundancy in the statistical sampling of the molecular trajectories, and (b) transforming the integrals for the orbital variables so that the singularities of the integrands at the turning points are eliminated. An asymptotic theory of the line shape developed earlier for atomic spectra is extended to molecular spectra. Results are given for the atomic species, due to overlap induction, at the reduced temperatures T* = 1, 2, 4, 5, 10, 15, and for the molecular species, due to quadrupolar, octopolar and hexadecapolar induction, at T* = 1, 2, 4. The agreement between the simulated and theoretical spectra is excellent.