Subpicosecond ultraviolet multiphoton electron spectroscopy of rare gases

The line positions and linewidths of photoelectron spectra arising from multiphoton ionization are analyzed for the first reported time in the subpicosecond (0.5–1.0-psec) region. Measurements performed with 248-nm radiation at intensity level for which the quiver energy of the free-electron motion is comparable with the photon energy are an reported. The short-pulse property causes the photoelectron energy to become a dynamical variable associated with the process of ionization and significantly influences both the line positions and the linewidths of the observed electron spectra.