Theoretical study of intramultiplet transitions in collisions of atoms inP3electronic states with structureless targets:Ca(P3)+He

Abstract

The quantum close-coupling (CC) treatment of collisions of an atom in a $^{3}P$ electronic state with a structureless target is developed, based on earlier work of Mies [Phys. Rev. A 7, 942 (1973)] and a ${j}_{z}$-conserving [coupled-states (CS)] simplification presented. There is no direct coupling between the $J=0$ and $J=1$ levels; transitions between these levels will occur only as a result of Coriolis coupling involving the $J=2$ state. Actual CC and CS calculations are reported for collisions of $\mathrm{Ca} 4^{3}P^{o}$ with He, based on the potential curves of Malvern [J. Phys. B 11, 831 (1978)]. In the CC results, of the three independent cross sections, $J=2\ensuremath{\rightarrow}1$ is predicted to be largest, and $J=2\ensuremath{\rightarrow}0$ smallest, over the entire range of collision energies sampled. By contrast, the CS approximation predicts the 1\ensuremath{\rightarrow}0 transition to be forbidden, and yields only fair accuracy for the CC 2\ensuremath{\rightarrow}1 and 2\ensuremath{\rightarrow}0 transitions. The coupling between spin-orbit states is also interpreted within an adiabatic model. A comparison with the experimental results of Yuh and Dagdigian (preceding paper) is made by averaging the CC cross sections over the experimental translational energy distribution. The experimental cross sections for the 2\ensuremath{\rightarrow}1 and 2\ensuremath{\rightarrow}0 transitions are 3-4 times larger than the theoretical values, and the 2\ensuremath{\rightarrow}0 cross section is found experimentally to be \ensuremath{\sim}3 times larger than the 1\ensuremath{\rightarrow}0 cross section, in direct contrast with the theoretical prediction for this ratio.