a.c. Stark shifts in resonant multiphoton ionization of nitric oxide

Abstract
Measurements of a.c. Stark shifts and broadening have been made on several two-photon resonant rovibronic levels in nitric oxide, with use of resonance multiphoton spectroscopy with a calibrated proportional-counter system. Contrary to a similar study recently published [Li, Porter, and Johnson, Phys. Rev. Lett. 53, 1336 (1984)], a.c. Stark effects are found to be independent of pressure. However, we find that space-charge effects in ionization detectors can strongly influence observed line shape at high target gas density and high laser intensities.