Effects of collisional broadening and radiative recombination on the time dependence of initial-state population of a photoexcited autoionizing atom

The effects of collisional broadening and radiative recombination on the temporal behavior of the initial-state population $P_0\mathrm{}\left(t\right)\mathrm{}$ are examined for a photoexcited autoionized atom. The results show the existence of coherent or dissipative regimes whenever the Rabi oscillations or relaxation rates dominate, respectively. Radiative recombination tends to increase the lifetime of $P_0\mathrm{}\left(t\right)\mathrm{}$ while collisional broadening has the reverse effect. A simple approximation for $P_0\mathrm{}\left(t\right)\mathrm{}$ is suggested and demonstrated to be excellent in the dissipative regime.