Photo-double-ionization of the the 2s-22p6(1Se) state of Ne

P. BOLOGNESI, G. ALBERTI, I. BRAY, S. OTRANTO, C. R. GARIBOTTI, R. FLAMMINI, A. KHEIFETS Y L. AVALDI

Rosario, Argentina

Conferencia; XXIV International Conference on Photonic Electronic and Atomic collisions (ICPEAC); 2005

  The ejection of two electrons of an atom by absorption of a single photon, i.e. the photodouble ionisation (PDI), is one the fundamental few body processes in atomic physics. The archetypal system to study this process is the He atom, because the final doubly charged ion state has the simplest 1Se symmetry and the final state of the electron pair is of pure 1Po symmetry. A similar condition can be found in the PDI of the s orbital of heavier rare gases, the only difference being that now the two s-electrons are ejected from an inner-valence shell. In the present contribution we report on recent measurements of the triple differential cross section (TDCS) of the He2+(1s‑2) and Ne2+(2s‑2) states at ~20 eV above their respective double ionisation thresholds, measured in equal and unequal energy sharing condition and perpendicular geometry. The aim of the experiment is to investigate whether the TDCS is purely determined by the symmetry of the final ionic state and the configuration of the electron pair or the internal structure of the residual ion plays a role. The results are compared with the CCC [1] and the recently introduced SC3 model [2]. The differences that can be observed between the He and Ne case can be interpreted as due to the different initial state wave functions and for the first time we have observed that the coincidence angular distributions can be used to discriminate among different initial state wave functions. References [1] A.S. Kheifets and I. Bray  Phys. Rev. Lett. 81 (1998) 4588 [2]  S. Otranto and C.R. Garibotti Europ. Phys. J. D 21 (2002) 285 [3] P. Bolognesi et al. Phys. Rev. A70 (2004) 62715 Figure1 : TDCS in equal energy sharing [3] compared with the SC3 calculations using an initial state without angular correlation (dashed line), with angular correlation (dotted line) and a mixed 2s-2p initial state as suggested in [3] (solid line).           Figure 2 : TDCS in unequal energy sharing compared with the CCC calculations.