Studies on coherent effects in double-resonance multiphoton ionization of sodium with pulsed lasers

An experimental study of doubly resonant multiphoton ionization of Na has been carried out. Coherence effects, such as AC - Stark splitting and population trapping, have been manifested in different coupling schemes, i.e. ladder, lambda, vee configurations. These effects have been investigated in terms of their dependence on the laser intensity and resonance detuning, as well as the state of the laser polarization. The experimental results are qualitatively interpreted in terms of a few level system.