Photodouble ionization differential cross sections for D2 with various electronenergy sharing conditions

Abstract

The mutual angular distributions of the two ejected electrons following directphotodouble ionization have been measured for D2 at an excess energy(E)of 25 eV using linearly polarized light. These (γ,2e) ‘triple’ differential cross sections (TDCSs) were obtained forasymmetric electron energy conditions with energy sharing ratios(R = E2 /E1)of R = 24, 11.5, 4and 2.57. In all cases the ‘reference’ electron (energy = E1)was oriented along the direction of the electric field vector(\U0001d6c6) anddetected in coincidence with a second electron (energy = E2) coplanar with \U0001d6c6 and the photon beamdirection (kγ). For comparison,helium TDCSs were obtained for the sameE andRvalues under nearly identical spectrometer conditions. Theseshow very good agreement with the results of hyperspherical-ℜ-matrixwith semi-classical outgoing waves calculations, thus providing even moreconfidence in the D2 TDCSs where there is as yet no accurate ab initiotheory. The similarities and differences between the experimental resultsassociated with the two targets are qualitatively discussed in terms ofFeagin’s model (Feagin J M 1998 J. Phys. B: At. Mol. Opt. Phys. 31 L729).