Simultaneous Double Ionization Research Articles

Simultaneous double ionization of C60 molecules in single-cycle pulses

We theoretically investigate simultaneous double ionization of C60 Buckminsterfullerene clusters within the strong field approximation, taking into account two-body effects like Coulomb blocking. Our analysis suggests that for infrared single-cycle pulses, simultaneous double ionization becomes comparable in magnitude to sequential double ionization. Additionally, estimates show that Coulomb blocking weakens with increasing cluster size and field strength.

Excitation of Lanthanum and Lutetium Double-Charged Ions in Electron-Atom Collisions

Excitation of LaIII and LuIII in collisions of slow electrons with La and Lu atoms (excitation with simultaneous double ionization) have been studied in experiment. At exciting electron energy of 50 eV at 19 excitation cross-sections for each of LaIII and LuIII were measured. At two optical excitation functions for both of ions were recorded, in the electron energy range of 0–200 eV for LaIII and in the range of 0–250 eV for LuIII. Absolute values of excitation cross-sections for similar levels of LaIII and LuIII are compared.

K-shell andL-shell(e,3e)double ionization of beryllium by fast electron impact

We report fully differential cross sections for simultaneous double ionization of atomic beryllium by fast electron impact. We analyze separately the two ionization channels that leave the dication in either the $2{s}^{2}$ autoionizing excited state or its $1{s}^{2}$ bound ground state. For the double continuum, owing to the two slow emitted electrons, we employ the three-pairwise-Coulomb-interaction model (3C) along with the first Born approximation. Aiming to probe the hitherto largely unexplored role of the electron correlation in $(e,3e)$, we determine and check fully correlated, compact analytical wave functions, satisfying all two-particle Kato cusp conditions for the four-electron Be initial state and the two-electron ${\text{Be}}^{2+}$ final states, as well as other, much or little or noncorrelated, functions, issuing from either analytic global optimization or Hartree-Fock theory. We point out similarities or contrasts with trends observed in the double photoionization, allowing for parallels between $(e,3e)$ and $(\ensuremath{\gamma},2e)$. Various numerical examples serve to navigate possible future experiments in the nonrelativistic regime of the ionization problem.

Ionization of helium by a short pulse of radiation: A Fermi molecular-dynamics calculation

We describe the results of our quasiclassical calculations of the ionization probabilities of a helium atom, exposed to a short pulse of linearly polarized laser radiation. The technique known as Fermi molecular dynamics was applied. Of particular interest was our observation of the signature of a new process of double ionization, at relatively low laser irradiances. We interpret this as a signature of the simultaneous double ionization of helium. This new process was found to proceed in competition with sequential double ionization. The simultaneous double ionization of helium, as a distinct process at relatively long wavelengths, has just been discovered experimentally [D. Fittinghoff, P. Bolton, B. Chang, and K. Kulander, Phys. Rev. Lett. 69, 2642 (1993)].

Low Energy Auger Electrons - a Probe of Electron Correlations in Atoms and Molecules

Until very recently Auger decay was exclusively regarded as an inner-shell phenomenon. However, recent studies of the decay of certain valence states in atoms and molecules excited by electron correlation accompanying photoinization have shown the importance of non-radiative decay processes, so-called particular Auger transitions. The fact that such states decay non-radiatively was previously ignored, and is of critical importance for the interpretation of double-photoinization data, for both, photoion yield measurments, particularly near threshold, and photoelectron spectra, especially at low kinetic energies. Hence the spectroscopy of these participator Auger transitions is of considerable interest for our understanding of electron correlations. Two modes of such transitions were identified; the inner-valence type in which the inner vs hole is filled in the decay process, and the valence-multiplet type in which the valence shell remains unchanged in occupancy during the transition, but experiences a change of LS multiplet symmetry. The analysis of these processes shows that in the sudden limit up to 30-40% of the double-ionization rate in neon and argon is due to particular Auger decay, which was previously attributed to simultaneous double ionization.

Absolute cross sections for excited Ba iii states produced by single-electron impact from Ba i

Absolute cross sections for simultaneous double ionization and excitation of Ba by electron impact have been measured in a crossed-beam experiment. The lines investigated are at 74.3, 58.7, and 55.5 nm. The vacuum-ultraviolet system was calibrated using a single-ionization chamber. Absolute cross sections were derived by comparison with the known excitation function of the Ba I resonance line at 553.5 nm.