Interferences in the3p4nlsatellite emission following the excitation of argon across the2p1∕254sand2p3∕253dJ=1resonances

Abstract

The intensity and angular distribution of the argon $3{p}^{4}nl$ photoelectron lines have been measured with a high resolution (of about $55\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$) in the $246.51--246.93\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ photon energy region. For these photon energies, the excitation of the $2{p}_{1∕2}^{5}4s$ and $2{p}_{3∕2}^{5}(3d+5s)$ $J=1$ intermediate resonances leads to a remarkable (interference) pattern in the intensity of the observed fine-structure states of the satellite lines, which can be attributed to a coherent interplay between the direct photoionization and various excitation-autoionization channels. Detailed computations show that this behavior in the observed electron intensities can be understood only if both the overlap of the resonances as well as their relative phases are taken into account. For these photon energies, therefore, any accurate description of the photoionization (with excitation) requires going beyond the two-step model, which separates the excitation process of the atoms from the subsequent photoelectron emission. Reasonable agreement between experiment and theory is found for most lines by applying multiconfiguration Dirac-Fock wave functions. Apart from a first quantitative analysis of the $3{p}^{4}nl$ electron lines, however, the high photon and electron energy resolution of the present experiments may stimulate future investigations on resonance phenomena in atomic photoionization, including rearrangement effects in the bound-state electron density and a refined treatment of the electron continuum.