STRONG FIELD EFFECTS IN THE SPECTROSCOPY OF THE B RYDBERG STATE OF CH3I

One- and two-color molecular beam resonance-enhanced multiphoton ionization (REMPI) excitation spectra of the Rydberg B̃ state of CH3I revealed pronounced strong field effects manifested by apparent splittings in the molecular line shapes, appearance of new transitions, and large frequency shifts. The splittings or dip features occur in a saturation broadened regime due to a competition between rates of predissociation and photoionization from the B̃ state origin, the latter of which varies with the temporal intensity profile of the laser pulse. The dip can be made to disappear and the line width to narrow by the introduction of a second intense ionizing pulse. Appropriate rate equations were integrated to simulate the predissociation line shape and other observed trends. © 1990 American Chemical Society.