Electron-correlation-induced interchange of lifetime broadenings of 5s-1 multiplet states in atomic Cs

The lifetime broadenings of the most intense 5s photolines of Cs were studied. The aim of this study was to understand the origin of the remarkable differences in the lifetime widths of different 5s-1 multiplet states. The 5s photoelectron spectra of the 6s→6p1/2,3/2 laser-excited states are presented in the binding energy region of 30-34 eV showing the main 5s photolines of the ground state and laser-excited states as well as the 5s5p66p shakeup satellites. The lifetime widths of the states were determined. The Hartree-Fock calculations were carried out to predict the 5s photoelectron spectrum. The lifetime broadenings of the 5s photolines were found to be due to the transition rates of the subsequent Coster-Kronig transitions to the 5s25p5 states. It was found that a straightforward single-configuration explanation cannot be given for the lifetime differences. Instead, electron correlation plays an essential role and the lifetime broadenings were found to be predicted well only when configuration interaction between the 5s-1 and 5p-25d configurations is taking into account.