Abstract

Energy levels of an atom in a laser field are shifted by the ac Stark effect,¹ which in turn causes shifting at the peak frequency of a multiphoton transition spectra and changing the line shape of ionization spectra. Usually a laser beam has some temporal and spatial distribution and accordingly an atom interacting with a laser sees a nonuniform intensity. In a previous study,² it was shown that the shift of ionization peak frequency is considerably less than the theoretical prediction due to the nonuniformity of laser beam implying that measurements of an ac Stark shift cross section without consideration of detailed laser characteristics may lead to incorrect results.

© 1998 Optical Society of America