Femtosecond laser control of the angular distribution of electrons due to autoionization

Abstract

Using two 500-fs laser pulses and a controlled time delay between them we are able to manipulate the angular distributions of the electrons ejected by autoionization of Ca atoms in the $4{p}_{3∕2}21s$ and $4{p}_{3∕2}19d$ states. Subsequent to their isolated core excitation by a 500-fs 393-nm laser pulse, $\mathrm{Ca}\phantom{\rule{0.3em}{0ex}}4{p}_{3∕2}21s(19d)$ Rydberg atoms coherently evolve, via configuration interaction, into the degenerate $4{p}_{1∕2}ns(nd)$ states. While in the $4{p}_{1∕2}ns(nd)$ states atoms can be de-excited to bound $4sns(nd)$ levels using a 500-fs 397-nm pulse. Removing these atoms from the autoionizing states leads to a greater fraction of electrons leaving the atom along the direction of the laser polarization than is possible through direct excitation of ${4}_{3∕2}ns(nd)$ or $4{p}_{1∕2}ns(nd)$ using either the 393- or 397-nm pulse alone.