Photo-double-ionization of He: Fully differential and absolute electronic and ionic momentum distributions

Abstract

We measure fully differential cross sections for photo-double-ionization of helium at energies 1, 6, and 20 eV above threshold. The data have been obtained by measuring in coincidence the momentum vector of the He 2ϩ ion and one of the electrons. Using time-of-flight and imaging techniques, we cover a solid angle of 25-100 % 4 of the final-state continuum of all particles. Therefore the experiment is not confined to any particular set of angles or energy sharing, and allows for a reliable absolute calibration. We present momentum distributions of the ions and a comprehensive set of differential cross sections for electron emission. The latter are on an absolute scale and cover both equal and unequal energy sharing-for both the fast and the slow electron fixed-and a wide range of polar angles. We also present the first data for noncoplanar geometry. For all energies the cross section is sharply peaked around the coplanar emission, i.e., both electrons are preferentially emitted in the plane of the recoiling ion and the photon polarization direction. For most of the geometries the shape of the cross sections is well described by fourth-order Wannier theory calculations.

Complete photo-fragmentation of the deuterium molecule

“…The momenta, i.e. the set of vectors, of all the fragments of an atom or molecule break-up can be measured in coincidence with high precision using state-of-the-art imaging and timing techniques [16]. These asymptotic many-particle momentum distributions are determined by the interaction inducing the fragmentation, the bound initial state from which it emerged, and the interactions between the outgoing particles.…”

Cross sections for short-pulse single and double ionization of helium

“…9 are the results from ref. [25] obtained using fourth-order Wannier theory [26], which do not provide absolute cross sections but evidently do reproduce the shapes of the TDCS at these low energies. Fig.…”

“…The TDCS are plotted in Fig. 9, along with absolute experimental results of Dorner et al [25]. In the experiment, the data was binned over finite ranges of energy sharing( 0-0.2, 0.5 and 0.8-1) and polar angle θ 1 (40-65 • ) for the fixed electron.…”

“…Solid curves: present results; experimental results (dots) and fourth-order Wannier theory results (broken curves) are from ref. [25].…”

Hydrogen and fluorine migration in photo-double-ionization of 1,1-difluoroethylene (1,1-C2H2F2Gaire1, Bocharova2, Sturm3 et al. 2014Phys. Rev. ASelf Cite41130View full textAdd to dashboardCite

“…In the indirect process (sometimes also referred to as a sequential process), photoejection of one electron leads to an intermediate cation state, which later decays by autoionization or other processes (e.g., Auger decay, fluorescence, etc.). After a couple of decades of studying the PDI of simple atoms and diatomic molecules (e.g., He, H 2 , N 2 , CO) in great detail [2][3][4][5][6][7][8][9][10], the investigation has been extended to polyatomic molecules in order to gain a general understanding of the double-ionization process in more complex systems. Simple hydrocarbon molecules are an ideal testbed for a series of studies with increasing complexity.…”