Inelastic processes in collisions of Na(3s,3p) with He at thermal energies

摘要

Inelastic collisions of sodium due to low-energy helium are investigated using the quantum-mechanical molecular-orbital coupled-channel method. The calculations adopt adiabatic potentials and nonadiabatic radial and rotational couplings obtained with the multireference single- and double-excitation configuration interaction approach. The potentials are fitted to long-range dispersion coefficients and adjusted with a model interaction in the van der Waals well region. Collisional cross sections for energies between 0.001 eV and 10 eV and rate coefficients as a function of temperature between 10 K and 10 000 K are obtained for Na(3p -> 3s) quenching and Na(3s -> 3p) excitation. The results are relevant to modeling non-LTE effects in Na D absorption lines in extrasolar planets and brown dwarfs.