High-energy behavior of the double photoionization of helium from 2 to 12 keV

Abstract

We report the ratio of double-to-single photoionization of He at several photon energies from 2 to 12 keV. By time-of-Aight methods, we find a ratio consistent with an asymptote at 1.5%+0.2%, essentially reached by h v=4 keV. Fair agreement is obtained with older shake calculations of Byron and Joachain

Analytical evaluation of cross sections for double ionization of heliumlike ions by high-energy-photon scattering

“…At present, the most accurate calculations give Rp = 1.67% for the helium atom at to I. The theoretical result is in agreement with experimental measurements [3]. However, at to > 7 keV, the ejection of electrons from the helium atom proceeds mainly due to the scattering, but not due to the absorption of photons.…”

Double ionization of He by high-energy photon impact

“…+, of the double-to single-photoionization cross sections of He by use of an accurate initial-state wave function and an approximate final-state wave function and to understand the role of the FSC at the photon energy E =1.0-12.0 keV. The results will be compared with the very recent observations using synchrotron radiation by Levin and co-workers [8,9].…”

“…ri& @~0+ q(g;r, r')= e " I (1irj) 4rr' X [(r+r') &F&(irt;3; -2ip(r+r')) -~r r'~', F,(ig;3; --2ip~r r'~) . - (9) q & "00 and qo 0 & ". have no contribution to the cross section due to the geometric condition with respect to r and…”

“…As E increases, however, the energy sharing of the two ionized electrons become very asymmetric and the electron-energy distribution becomes concentrated on the ', respectively. Experimental data [8,9,23] are shown by the solid square, the solid circles, and the open circles, respectively.…”

“…The single-photoionization cross section is obtained by using the Hartree-Fock wave functions for the initial and the final states [7]. Figure 1 shows the data taken from Table I as well as the existing experimental results in keV region of E [8,9,23]. Hereafter, one refers to the ratios with and without introduction of the FSC of Eq.…”