Photoionization of confined Ca in a spherical potential well

Abstract

The photoionization cross section of the Ca atom, confined by a spherical annular potential, has been calculated using a modification to the Belfast R-matrix code for a variety of depths of the confining potential. The results show that the external potential affects the cross section, which is dominated by doubly excited autoionizing states, quite significantly, causing much of the oscillator strength to move into the discrete region of the spectrum. In addition, increasing well depth causes a level crossing between the first two excited states of Ca+, thereby changing the ordering of resonances dramatically. The calculation for free Ca shows excellent agreement with experiment. DOI: 10.1103/PhysRevA.87.013409