Laser-induced continuum structure and population trapping in helium (2s/sup 1/S/sub 0/)

Summary form only given. We present experimental observations along with theoretical modeling of laser induced continuum structure (LICS) in helium. The excited state 4s/sup 1/S/sub 0/ is coupled to the ionization continuum with strong laser radiation at 1064 nm. The induced continuum structure is detected by ionization of the state 2s/sup 1/S/sub 0/ with a weak laser pulse at 294 nm. Enhancement as well as strong reduction of ionization due to trapping of population can be observed. We demonstrate how LICS structures move about in a systematic way as a result of the AC Stark effect and power broadening. Quantitative comparison between theory and experiment is possible because of the high spectral resolution achieved in this experiment.