Abstract
An optimum laser intensity that maximizes the photoionization yield is found in a two-photon resonant, three-photon ionization experiment. At laser intensities higher than this optimum, a negative value is obtained for the exponential index describing this multiphoton process, both at zero detuning and at the detuning for which the signal is maximized. Despite the presence of large (> 1 ÅA) optical Stark shifts, Gaussian beam-focusing effects produce an excitation spectrum peaked near zero detuning and reverse the sense of its skewness.
- Received 1 August 1984
DOI:https://doi.org/10.1103/PhysRevLett.54.309
©1985 American Physical Society
