Radiative de-excitations of the 1s2s3s configuration of Li-like ions

The fully relativistic configuration interaction method is used to study the one-electron one-photon (OEOP) and two-electron one-photon (TEOP) transitions between the 1s2s3s and the respective 1s2s2p and 1s ²np (n = 2–4 ) groups of Li-like ions with 12 ≤ Z ≤ 54. The transition properties are calculated using multi-configuration Dirac–Fock wavefunctions in the active space approximation taking into account the correlated state functions that have non-negligible contributions to the mixing coefficients. The drastic variations in the level lifetimes due especially to 1s2s3s-1s ² np (n = 2, 3) transitions are analyzed in detail. The OEOP transition energies are far less than those of TEOP transitions and have been taken up in this work mainly to investigate the most probable radiative decay channel and also to understand the interplay between electron–electron correlation and the low-frequency limit transverse photon interaction on the mixing coefficients of J = 3/2 states of 1s2s2p around Z = 21. The present results are compared with other available data. (paper)