Depolarisation rates of Ca II s, p and d levels by isotropic collisions with hydrogen atoms

Abstract

Multipole relaxation and transfer rates of the 4s 2 S, 3d 2 D and 4p 2 P states of Ca  due to isotropic collisions with neutral hydrogen atoms are calculated. Evaluation of these rates have been carried out using accurate ab initio potential en- ergy curves. The collisional T-matrix elements required for these calculations have been evaluated in a quantum mechanical description including fine structure splitting. Analytical expressions of all the rates valid for 200 K ≤ T ≤ 10 000 K are given.