Experimental and theoretical confirmation of the role of higher order mechanisms in the electron impact double ionization of helium

E M Staicu Casagrande (1) , C Li (1) , A Lahmam-Bennani (1) , C Dal Cappello (2) , M Schulz (3) , M Ciappina (4)

1 ISMO - Institut des Sciences Moléculaires d'Orsay
2 Institut de Physique
3 Dept. of Physics and LAMOR
4 IHPC - Institute of High Performance Computing

Our recent measurements [ Lahmam-Bennani et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 105201 ] of the (e, 3-1e) four-fold differential cross sections (4DCS) for double ionisation of helium are here extended to a wider range of ejected electron energies and very asymmetric energy sharing. The previous observations of large angular shifts in the experimental 4DCS distributions with respect to the momentum transfer axis are once again reproduced by the new measured data. Moreover, comparison of all the data sets with the kinematical analysis previously given and with two newly developed non-first order theoretical models for double ionisation, namely 'the two-step2 - Monte Carlo Event Generator (TS2-MCEG) and a second Born approximation (B2) confirms our interpretation which allows relating the observed shifts and the existence of structures in the intensity distributions mostly to the second order, 'two-step 2 ' (TS2) double ionisation mechanism, which is shown to predominate over the first-order 'shake-off ' (SO) and 'two-step 1 ' (TS1) mechanisms under the present kinematics. 3

Mots clés: Physical Sciences

E M Staicu Casagrande, C Li, A Lahmam-Bennani, C Dal Cappello, M Schulz, et al.. Experimental and theoretical confirmation of the role of higher order mechanisms in the electron impact double ionization of helium. Journal of Physics B: Atomic, Molecular and Optical Physics, 2011, 44 (5), pp.55201. ⟨10.1088/0953-4075/44/5/055201⟩. ⟨hal-00600136⟩