Enhanced double ionization with circularly polarized light

Using 120-fs, 800-nm Ti:sapphire laser pulses, ionic yields of singly and doubly charged magnesium ions were measured as a function of intensity and laser field ellipticity. A clear nonsequential enhancement of the doubly charged ion is observed for circularly polarized light in addition to linearly polarized light. Over the entire intensity range the double-ionization yield is considerably higher for linear polarization than it is for circular polarization.