Mechanisms of configuration interaction in relativistic autoionisation: threshold phenomena and the Li⁴P_Jlevels

Abstract

The authors have calculated the relativistic autoionisation of the low-lying 4P/sub /J levels of Li using the state-specific theory with the Breit-Pauli Hamiltonian. The results provide a definitive explanation of the shorter lifetimes of metastable Li quartets above the Li+ 1s2s 3S threshold compared with the theoretical predictions from the radiative transition probabilities. This discrepancy between previous theory and experiment is explained in terms of the indirect mechanism of relativistic autoionisation, which is suddenly enhanced-as a result of symmetry, electron correlation and non-orthonormality effects-as the 1s2s 3S channel opens up. The explanation of the threshold effect is thus based on a configuration interaction mechanism and not on a low-energy electron emission effect recently proposed by Mannervik and Cederquist (1986).