Interference effects on intense XUV pulse induced resonant transitions between core ionized states of helium

Abstract

In the context of core-resonant ionization of helium atom the inclusion of the He–He+(2p) ionization channel sets off a quantum mechanical interference between two competing pathways, He–He+(1s)–He+(2p) and He–He+(2p) (He–He+(1s) and He–He+(2p)–He+(1s)), thereby significantly modifying the line shape of the photoelectron spectrum. The signature of this interference arises as an asymmetry in the line shape of the multi-peak photoelectron spectra. On account of the discrepancies over the magnitude of the two photon photoionization cross section for the He–He+(2p) ionization channel the calculations have been performed for three different magnitudes of this photoionization cross section and the findings confirm that asymmetry in the line shape is prevalent for all the chosen cross sections. However, the magnitude of asymmetry depends on the magnitude of the photoionization cross section for the He–He+(2p) ionization channel. It is also interesting to note that at the considered laser peak intensities in this work an additional ionization channel from excited ionic state of helium plays a significant role in influencing the line shape of the photoelectron spectrum. The effects of pulse duration on the line shape of the photoelectron spectrum and the possibility to control the interference induced asymmetry in the multi peak line shape has also been investigated.