Collision models of intramultiplet transitions at thermal energies

Abstract

An analysis is presented of the range of validity of the approximations currently used to calculate cross sections for fine-structure transitions at thermal energies. The particular example considered is the 2P1/2-2P3/2 transition in C+-H collisions. For a given set of interaction potentials of CH+, the full quantum-mechanical close-coupling method is used to provide a reference for comparison with a number of approximate dynamical models-semiclassical sudden approximation, quantal elastic and Omega -conserving methods. All of the dynamical models examined proved to be very satisfactory. On the other hand, the calculated cross sections are sensitive to the interaction potentials, especially for intermediate and long internuclear distances where the presently available data are not sufficiently reliable; errors in the calculated cross sections may attain 40%.