Abstract

Photoelectron energy spectra from multiphoton ionization, when taken with ultrashort pulses (<ps), have been shown¹ to reveal the resonant character of the transitions, while this effect remains hidden with longer pulses. The resonances are induced by ac Stark shifts and produce structures in the electron energy spectra. The amplitudes of the structures depend on the pulse peak power but not on their positions (in energy), which depend only on the static detuning of the resonance and the various Stark coefficients.

© 1990 Optical Society of America