Double photoionization of helium using many-body perturbation theory

Abstract

Cross sections for double photoionization of He are calculated using the lowest-order many-body perturbation theory. There are three amplitudes contributing in the present calculation. They represent the three mechanisms for double ionization, namely, two-step-1, shake off, and groundstate correlation. It is explicitly shown that the cross section for each of these mechanisms depends strongly on the adopted form of the dipole interaction as indicated by Dalgarno and Sadeghpour [Phys. Rev. A 46, 3591 (1992)]. Our final results obtained by the sum of three amplitudes do not depend on the choice of the dipole formula at photon energies above 1 kev. The ratios of the cross sections for double ionization to single ionization are in excellent agreement with recent experimental results at energies 2 -12 keV.PACS number(s): 32.80.pb, 31.20.d

Instability of dynamic localization in the intense terahertz-driven semiconductor Wannier-Stark ladder due to the dynamic Fano resonance

“…It should be noted that the KH transformation is considered to be a gauge transformation that is closely related to the acceleration form of an optical dipole interaction [48]. Further, it should be noted that…”

Photoinduced K-shell hollow atoms

“…Further, ground-state electron correlations are important for the shake-off, whilst the final-state electron interactions govern the dielectronic process. Although qualitatively the two mechanisms have very different photon energy dependences and different electron interaction times, the separation of KO and SO and quantification of the interferences is not straightforward (see e.g., [7,10,41,42,11,43]). In comparison to He and He-like ions, much less theoretical effort has been devoted to the DPI of neutral atoms.…”

“…In the KO process, the outgoing photoelectron knocks out the second 1s electron in an (e, 2e)-like electron impact halfcollision. Although the dependence of the two mechanisms on the incoming photon energy is very different, in most cases it is hard to distinguish the contributions of the two processes and attempts to separate them have given rise to intensive research [7][8][9][10][11][12][13].…”

Double K-Vacancy Production by X-Ray Photoionization

“…Calculation of the double-to-single photoionization ratio R as a function of photon energy provides a testing ground for the development of theories that incorporate electron correlation in the ground state and in the final continuum states [2,3]. Among several theoretical approaches [3], the many-body perturbation theory (MBPT) [4] provides a description of the double-photoionization process in terms of three first-order amplitudes in the electron-electron interaction (see [2,3] for discussions of the MBPT). The three lowestorder MBPT diagrams are referred to as GSC (ground state correlation), SO (shake off), and TS1 (two-step one).…”

“…The amplitudes are also gauge dependent, i.e., they depend on the form of the dipole operator used (length, velocity, or acceleration), a topic that has been discussed in the theoretical literature ( [2,3,6]). Nevertheless, it is informative to consider the energy dependencies of the three amplitudes in the acceleration form of the dipole operator [4] which gives better agreement with the measurements of [1] than the length and velocity results. All three amplitudes increase strongly from threshold, but the GSC and SO amplitudes level out asymptotically, while the TS1 amplitude passes through a maximum and decreases monotonically to high energy.…”