PEAK ASYMMETRY OF AC STARK SPLITTING IN RESONANT EXCITATION OF MULTILEVEL SYSTEMS DUE TO THE EXISTENCE OF NEAR-DEGENERATE STATES

Calculation on resonant excitation of a four-level system with a pair of near-degenerate intermediate states is presented. It is shown that due to the presence of these near-degenerate states, reversed peak asymmetry and asymmetric absorption(ionization) profile is obtained.