The influence of relativistic effects on the lifetime of the 5s5p6 2S1/2 state of Xe II

The lifetime of the 5s5p6 2S1/2 state in Xe II has been calculated using an eigenvector for the 2S1/2 state determined by parametric fitting to the lowest even configurations. Due to the extreme destructive interference in the line strength, the lifetime is very sensitive to the eigenvector composition. An earlier non-relativistic multi-configuration Hartree-Fock calculation gave a lifetime of 9.5 ns which is increased to about 35 ns in the present calculation. The latter value is in good agreement with a recent measurement. It has been noticed that the branching ratio in Xe II, which experimentally is known only approximately at present, appears to be even more sensitive to the eigenvector composition than the lifetime.