Electron angular distributions of noble gases in sequential two-photon double ionization

Abstract

We present an angle resolved study of photoelectrons emitted from ions of the noble gases neon, argon and krypton by means of time-of-flight spectroscopy. The ionic targets are generated in a sequential two-photon process induced by the free-electron laser FLASH. Values of the anisotropy parameters β2 and β4 are derived from electron angular distribution measurements in the photon energy range from 38 to 91 eV and compared to recent theoretical calculations.

Signatures of autoionization in the angular electron distribution in two-photon double ionization of Ar

“…These predictions by theory were tested by several experimental studies [10][11][12][13][14] (for a review see [15]). The angular distribution of the second electron ejected in SDI from the np 6 shells of Ne, Ar, Kr, Xe was measured for various photon energies by Braune et al [10].…”

“…Generally, experiment and theory are in satisfactory agreement, although there are deviations between them in some cases. Furthermore, disagreement among various calculations [9,14,16] based on non-relativistic and relativistic Hartree-Fock approaches and on the random phase approximation with exchange (RPAE) exist. The fine-structure np 5 2 P j doublet of the intermediate singly charged ion was considered both coherently and incoherently.…”

Atomic, Molecular and Cluster Science with the Reaction Microscope Endstation at FLASH2

“…The angular distributions of the ejected photoelectrons during two-photon double ionization (TPDI) were measured. The dominant TPDI channel observed was sequential double ionization (SDI), in which both photoelectrons were emitted from the argon atom by sequential single-photon absorption (see also [38]). The two photoelectrons were confirmed to be correlated through polarization of the intermediate Ar + state.…”

Symmetry breakdown of electron emission in extreme ultraviolet photoionization of argon

“…Most of the related experiments were employing ion spectrometry to be able to capture the highly charged reaction products 26 – 32 . Investigations of angularly resolved electron emission patterns can originate an even deeper access to the underlying processes 33 – 35 . Furthermore, merged X-ray-ion beams for ion yield determination via ion spectroscopy at synchrotron radiation sources have attracted broad attention 36 – 38 .…”