(2γ,2e) total and differential cross-section calculations for helium with ħω = 40–50 eVH. Bachau1 and B. Piraux2
1 Centre des Lasers Intenses et Applications, Université de Bordeaux I-CNRS-CEA, 33405 Talence Cedex, France
2 Laboratoire de Physique Atomique, Moléculaire et Optique, Unité PAMO, Université Catholique de Louvain, 2 chemin du Cyclotron, 1348 Louvain-la-Neuve, Belgium
We consider two-photon double ionization of helium and analyse the electron dynamics in the region where the process is direct (39.49 eV < ħω < 54.42 eV). The fundamental process of two-photon double ionization (TPDI) is far from being well understood. In order to gain physical insight into the dynamics involved in TPDI, we investigate the electron energy distributions for ħω = 46 eV and ħω = 50 eV, angular distributions are also analysed. The theoretical approach is based on the resolution of the time-dependent Schrödinger equation (TDSE), using a spectral approach. At the end of the pulse the TPDI probability is extracted from the total wavefunction using two different approaches. The first one neglects the electron interaction in the double continuum while the second one includes electron correlation effects. At ħω ≈ 45 eV the electrons are preferably emitted back-to-back with equal energy. At ħω = 50 eV the excess energy is likely to be transfered to one of the electron, while the electrons are emitted in opposite or same directions.
© EDP Sciences, Springer-Verlag 2009