Novel phenomena in very-low-frequency strong fields.
Atomic ionization by lasers of very low frequency, once thought to be a classical limit or a "tunneling limit", presents unique spectral features unlike any tunneling phenomenon. The identity of the atom is the controlling factor, leading to photoelectron spectra with well-defined peaks and valleys that persist over wide ranges of field parameters. Such a spectrum was observed 20 years ago in ionization of xenon at 10.6 microm.
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Max Born Institute, 12489 Berlin, Germany.