Inner-shell photoemission studies of lithium and sodium vapour

The complete electron spectra caused by photoionisation of Li and Na vapour in the 1s and 2p shells respectively, have been investigated in the region from 5 eV above threshold up to about twice the binding energy of the ionised electron. Even though the contribution of molecules to the vapour pressure was only of the order of a few per cent, molecular features are found in the experimental spectra with intensities comparable with the atomic structures. The interpretation of all features observed in the spectrum is given. In specific energy regions, where the molecular contributions do not disturb the atomic ones, a detailed study of the fine-structure branching ratio and of the satellite structure accompanying these ionisation processes has been made. The results of this investigation are compared with other experimental and theoretical data.