Using amplified 100 fs, 616 nm pulses, we employed pump-probe spectroscopy to investigate strong
field interactions with gases and metal surfaces. The ionization dynamics of a gas with a pump pulse foeused
to 1016 W/cm2 were deduced from spectral shifts in a probe pulse. In addition to above threshold ionization,
impact ionization and a nonlinear dependence of the collision frequency on pulse intensity are proposed
as mechanisms for the spectral shifts. Also, the cooling time of a high-temperature solid density
plasma was measured specifically, the nonequiibrium electron energy distribution excited by a resonantly
absorbed pulse focused to 5 x 1012 W/cm2 on a metal surface was measured with a photoelectron time-offlight
detector.
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