Quantum calculation of the pressure broadening of H and K lines of Ca+ calcium ion in a gaz of ground-state He helium atoms

Abstract

In this theoretical study, we have conducted calculations to investigate the pressure broadening of the H ( 4 s 2 S 1 / 2 − 4 p 2 P 1 / 2 ) and the K ( 4 s 2 S 1 / 2 − 4 p 2 P 3 / 2 ) lines of the Ca + calcium ion in a gas of ground-state He helium atoms. The focus of our work is to determine the profiles of the pressure-broadened resonance lines and analyse their behaviour under the influence of binary collisions between Ca + ions and He atoms. To achieve this, we constructed accurate potential energy curves for the ground X 2 Σ 1 / 2 + and the excited D 2 Π 1 / 2 , D 2 Π 3 / 2 and E 2 Σ 1 / 2 + states. Additionally, we constructed the corresponding transition dipole moments based on the data obtained through high-level ab initio methods, including SA-CASSCF, MRCI, and SO coupling, with Davidson and BSSE corrections. The study spans a range of temperatures from 4000 K to 12,000 K and wavelengths from 200 nm to 500 nm . The theoretical profile is characterised by dominant free-free transitions. In the vicinity of the 436 nm wavelength position, there is a satellite peak in the red wing, attributed to the contribution of D 2 Π 1 / 2 ⟵ X 2 Σ 1 / 2 + and D 2 Π 3 / 2 ⟵ X 2 Σ 1 / 2 + transitions. Our findings are in good agreement with previous theoretical results.