Collision-free multiple ionization of atoms and XUV stimulated emission in krypton at 193 nm

A description of studies involving collision-free multiple ionization of atoms and the observation of stimulated emission in krypton in the 90 - 100 nm region is given. The experiments, conducted at a wave-length of 193 nm, spanned the intensity range from about 10 to the 12th to about 10 to the 17th W/sq cm. On the basis of the coupling strength observed and the nature of the atomic states excited, a collective response of the atom involving the coherent motion of entire shells is strongly implicated.