Ab initio calculation of photoionization and inelastic photon scattering spectra of He below the N=2 threshold in a dc electric field.
We study the Stark effect on doubly excited states of the helium atom below N=2. We present the ab initio photoionization and total inelastic photon scattering cross sections calculated with the method of complex scaling for field strengths F <or= 100 kV/cm. The calculations are compared to the measurements of the ion [Phys. Rev. Lett. 90, 133002 (2003)] and vacuum ultraviolet fluorescence yields [Phys. Rev. Lett. 96, 093001 (2006)]. For the case of photoionization and for incident photons with polarization vector P parallel to the electric field F, we confirm the propensity rule proposed by Tong and Lin [Phys. Rev. Lett. 92, 223003 (2004)]. Furthermore, the rule is also shown to apply for F perpendicular to P and for the case of the inelastic scattering in both experimental geometries.
Mihelic
Andrej
A
Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. andrej.mihelic@ijs.si
Zitnik
Matjaz
M