Nonsequential two-photon double ionization of helium

Abstract

We present accurate time-dependent ab initio calculations on fully differential and total integrated (generalized) cross sections for the nonsequential two-photon double ionization of helium at photon energies from 40 to 54 eV. Our computational method is based on the solution of the time-dependent Schroedinger equation and subsequent projection of the wave function onto Coulomb waves. We compare our results with other recent calculations and discuss the emerging similarities and differences. We investigate the role of electronic correlation in the representation of the two-electron continuum states, which are used to extract the ionization yields from the fully correlated final wave function. In addition, we study the influence of the pulse length and shape on the cross sections in time-dependent calculations and address convergence issues.Comment: 14 pages, 10 figures; final version (acknowledgements and reference added, typos fixed

Two-photon double ionization of helium by attosecond laser pulses: Evidence of highly correlated electron motion

“…Provided one of the electrons is emitted perpendicular to the laser polarization direction, it is found that the angular distribution of the other electron is characterized by three lobes. The results are similar to those recently reported for the corresponding process in the hydrogen negative ion [R. The problem of direct (nonsequential) two-photon double ionization of helium has been studied extensively in recent years, as exemplified by numerous theoretical [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and experimental [19][20][21][22][23][24] works. This breakup process is fundamental in the sense that it is one of the simplest processes in nature where electron correlations are exhibited, manifested by a rather complex interplay between the electrons.…”

“…The problem of direct (nonsequential) two-photon double ionization of helium has been studied extensively in recent years, as exemplified by numerous theoretical [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and experimental [19][20][21][22][23][24] works. This breakup process is fundamental in the sense that it is one of the simplest processes in nature where electron correlations are exhibited, manifested by a rather complex interplay between the electrons.…”

Exploring few-photon, few-electron reactions at FLASH: from ion yield and momentum measurements to time-resolved and kinematically complete experiments

“…2. TPDI, which would be distributed along the lines parallel to the second diagonal [64,65], cannot be observed in the spectrum. ) second SDI steps are presented in Fig.…”

“…5. According to a series of calculations [51,56,57,[63][64][65]68,101], a change of the shape of the energy distribution between both electrons should be expected. As discussed, e.g., in [63], for the photon energies of 40-45 eV equal energy sharing between both emitted electrons is needed in order to overcome the attraction of the nucleus and promote both electrons into the continuum (see Fig.…”

TDDFT–Generalized kick perturbations and monitoring observables for calculation of excitation energies

“…One can use among others MC-HF [12], Hylleraas-type variational or coupled spherical harmonics calculations. We used the results of [13] especially adapted to our radial grid. The reconstruction schematically works in the following way:…”