Double ionization in the perturbative and tunneling regimes

Abstract

We have studied the doubly charged ion yields and electron energy spectra (normal and coincidence) for double ionization of atoms in two different ionization regimes (perturbative and tunneling). In both cases, the double-ionization rates appear to be anomalously large in some intensity range and strongly reduced by circular polarization. It is argued that these similar behaviors must result from different physical mechanisms.