Core-valence doubly ionized states: General aspects, examples, production mechanisms

Abstract

Largescale calculations of excitation energies in coupled cluster theory: The singlet excited states of benzene Reliable anisotropic dipole properties, and dispersion energy coefficients, for O2 evaluated using constrained dipole oscillator strength techniques Electronic double vacancies with one vacancy in the valence shell and one in the core play a role in several physical processes. Such core-valence double vacancies are theoretically analyzed and related to possible experiments. The corresponding wavefunctions and energies for CO, N 2 , and H 2 CO are computed using propagator and configuration interaction methods. The numerical results are analyzed in some detail and are compared to the corresponding single valence vacancies. The analysis is performed by breaking up the binding energy of the double vacancy into the most relevant components, such as hole-hole repulsion and relaxation contributions. It is shown that the double ionization potential is essentially given by single ionization quantities. In particular, we find a kind of ''Koopmans theorem'' for those dicationic states with an outer valence hole: the double ionization potential ͑shifted by the core ionization energy͒ is approximately given by the valence orbital energy of the core ionized state. As typical for double vacancies we encounter, in addition, an interesting singlet-triplet separation problem. Intensities for the production of the dicationic states by valence ionization out of a core ionized initial state are derived. The extent of valence hole localization in the dicationic states is analyzed by a two-hole population analysis. The analysis can be used to simulate the production of core-valence vacancies via Auger decay.

Double Core-Hole Production inN2: Beating the Auger Clock

“…2 (yellow shaded curve) predicts peaks at ∼410 eV, which are produced by the Auger decay of the main DCHSS state of N 2+ 2 involving mainly 2σ u and 1π u electrons. In light of the expected underestimate in theory of 2-4 eV due to partially unaccounted electron relaxation in the final states [24], the prediction agrees very well with the observed peak position. We conclude that the newly observed Auger electron signal at ∼410 eV kinetic energy stems from the decay of DCHSS states and is associated with so-called Auger hypersatellites [10,11].…”

Single and double ionization of the camphor molecule excited around the C 1s edge

“…The fact that the same fragment ions are observed using 70 eV electrons and 270 eV photons probably means that either the double ionization cross sections are still quite small at this photon energy or that the doubly ionized states decay very rapidly to singly ionized states through the fragmentation of the molecular ion. Cederbaum and collaborators have shown that there is an extremely high density of states associated with the double ionization of large molecules . The doubly ionized final states would in general be highly dissociative and have a very short lifetime.…”

“…Cederbaum and collaborators have shown that there is an extremely high density of states associated with the double ionization of large molecules. [36][37][38][39] The doubly ionized final states would in general be highly dissociative and have a very short lifetime. It has also been pointed out very recently [40] that, for excited states which tend to be energetically close to each other, the Born-Oppenheimer Approximation (B-O) does not hold.…”

Auger Electron Angular Distribution of Double Core-Hole States in the Molecular Reference Frame

“…We predict a range of $342-353 eV for the main tsDCH Auger electron energy based on our ab initio calculations. The measured energy should lie a few eV above this prediction since the calculations underestimate the relaxation energy of final states with core vacancies [26]. The Auger decay of dication states (N 2þ…”