Broadening of the sodium D lines by atomic hydrogen. An analysis in terms of the S matrix. (Solar photosphere)

The broadening and the shift of the Na D 1 and D 2 lines perturbed by atomic hydrogen are calculated taking into account accurate molecular potentials and non-adiabatic and fine structure effects. It is shown that the contribution of the ground state to the perturbed profile is predominant. The two components are broadened almost in the same manner whereas the shifts exhibit a difference of 20% at 4500K. The results obtained fit well with the observed wings of the absorption line profiles under the conditions of the solar photosphere. Cross sections for transitions induced between the fine structure states are calculated with and without taking into account the rotation of the internuclear axis. Non-adiabatic effects are shown to be of the order of 20%.