A new look at the retention of orbital alignment in collisions involving atoms in 1P electronic states: Ca(4sSp 1P) + He

Abstract

The retention of orbital alignment in collisions of Ca(4s5p 1P) atoms with He targets is examined anew, by inward propagation of the full wavefunction of the system, corresponding to a specifically prepared orientation of the p orbital, followed by projection of the incoming flux onto the Hund's case (a) Σ and Π states appropriate to the description of the molecular region. A previous error in the description of the initial state by Alexander and Pouilly has been corrected here. The results of the quantum flux redistribution calculations are virtually identical to the predictions of more conventional semiclassical impact parameter calculations, and, furthermore, are consistent with the concept of orbital locking, in which the initial space frame orientation of the p orbital is preserved until the collision partners attain the “locking radius”. However, locking is found to occur at values of the internuclear separation far smaller than would be predicted by somesimple models. Analysis of the flux redistribution and of the partial cross sections for the inelastic process Ca (4s5p 1P) → Ca(4s5p 3P) collisions are completely consistent with a model in which the transition probability is proportional solely to the flux in the 1Π state at the point of crossing with the 3Σ curve.