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

A description of studies invvolving 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 ∼1012−1017 W/cm2. On the basis of the coupling strength observed and the nature of the atomic states exccited, a collective response of the atom involving the coherent motion of entire shells is strongly implicated.