Theoretical investigation of the pressure broadening D1 and D2 lines of cesium atoms colliding with ground-state helium atoms

Abstract

Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field–multireference configuration interaction (SA-CASSCF–MRCI) calculations, involving the spin–orbit effect, and taking into account the Davidson and BSSE corrections. The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323–3000 K and 800–1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free–free transitions, and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to transitions. The results are in good agreement with previous experimental and theoretical works.