Photoionization and Compton Double Ionization of Helium from Threshold to 20 keV

Relativistic calculations of doubleK-shell-photoionization cross sections for neutral medium-Zatoms

“…The most widely studied quantity was the ratio of the doubleto-single photoionization cross sections σ ++ /σ + as a function of the energy of the incoming photon ω. Today, the helium double photoionization is often considered as well understood, and the results of several independent computations [2][3][4][5] agree reasonably well with the experimental data [6][7][8][9] in the whole region of the photon energies.…”

Absolute Photoionization Cross Sections of Excited He States in the Near-Threshold Region

“…The direct ionization of ground state He has been studied extensively and the photoionization cross section is very well understood theoretically and experimentally [2]. Other recent examples underlining its model character deal with interference effects in twoelectron excitations [3], circular dichroism in the double photoionization [4,5], new Rydberg series and resonances in doubly excited He [6], or photoionization and Compton double ionization up to photon energies of 20 keV [7].…”

Angular distribution in two-photon double ionization of helium by intense attosecond soft-x-ray pulses

“…Recently, the two-photon double-ionization and above-threshold ionization of helium were experimentally observed with the Ti:sapphire 27th harmonic pulses (photon energy 41.8 eV) [3]. These experimental advances open up the opportunity to revisit the dynamics of double ionization of helium by XUV photons previously investigated only in the singlephoton absorption and scattering regime using synchrotron radiation [4,5]. Simultaneous ejection of two electrons by a single photon allowed detailed tests of wavefunctions for the three-body Coulomb problem [6,7,8] and the role of electron correlations in strongly inelastic processes accompanied with near-zero momentum transfer (photoabsorption) or sizable momentum transfer (Compton scattering) [9,10].…”