Theoretical study of Ca(4s5p 1P)⇄Ca(4s5p 3P) transitions in collision with noble gases: Integral cross sections and alignment effects

Abstract

The present article describes fully quantum calculations of spin changing collisions of Ca(4s5p 1P)⇄Ca(4s5p 3P) in full collisions with all the noble gases (He, Ne, Ar, Kr, and Xe). The approach and scattering formalism follow our earlier article [J. Chem. Phys. 86, 4790 (1987)]. Flexible Morese-Spline–van der Waals functions are used to describe the relevant 1,3Σ and 1,3Π Ca*+M potential curves. The interpretation of the dependence of the cross section on initial polarization will be guided by diatomic spectroscopy and a consideration of the crossings between thse potential curves. The interpretation of the dependence of the cross section on initial polarization will be guided by diatomic spectroscopy and a consideration of the crossings between these potential curves. A new simple statistical model, based on the consideration of the reflection symmetry of the initially prepared state, will provide the point of departure for the prediction of the polarization dependence. The exact quantum cross sections agree well both with the predictions of the statistical model and with the recent experimental results from Leone’s laboratory at JILA. In addition the calculated 1P→3P cross sections increase with decreasing collision energy, since the crucial 1Π→3Σ crossing point is reached by the attractive branch of the 1Π potential.