Abstract

The interaction of atomic and molecular species with picosecond ArF* laser radiation is studied at intensities up to 10¹⁵ W/cm². Anomalously strong, collision-free multiple ionization is observed. Standard theoretical models of stepwise ionization fail to describe the results. The experimental findings point to a collective response of the atom. At intensities of ~10¹³ W/cm², selective multiquantum excitation of autoionizing states in Kr, followed by stimulated emission at wavelengths as short as 91.6 and 93 nm, is observed. The 93-nm radiation is tunable over a 600-cm⁻¹ interval, whereas the 91.6-nm frequency is fixed. It appears that electron collisions redistribute energy among excited states.

© 1984 Optical Society of America

Generation of infrared and extreme-ultraviolet radiation in krypton with picosecond irradiation at 193 nm

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