Coherence and partial localization in electron emission from HeH+ molecular ions

C. A. TACHINO; M. E. GALASSI; F. MARTÍN; R. D. RIVAROLA

Salamanca, España

Congreso; X European Conference on Atoms, Molecules and Photons; 2010

The interference patterns that appear in the electron emission spectra of diatomic molecules have their origin in the wavelike nature of the emitted particles. The first theoretical studies concerning this phenomenon were made by Cohen and Fano [1] in the decade of 1960. Since their pioneering work, numerous theoretical investigations were carried out with the objective of understanding the mechanisms that give rise to interference patterns. The first experimental confirmation of the existence of this effect was obtained by Stolterfoht et al. [2] at the begining of the present century for electron ionization of hydrogen molecules by impact of fast multiply charged heavy ions. Since then, more evidences of the existence of this phenomenon was obtained for impact of electrons, photons and ions on different diatomic molecular targets.In a recent work, we analyse theoretically the angular distribution of electrons resulting from the single ionization process of HeH+ molecular ions due to the impact of bare ions [3]. In that  opportunity, a coplanar geometry in which the emitted electron, the incident particle and the molecule are all in the same plane was considered. The dynamics of the collision reaction was described within the CDW-EIS model, and the final state of the electron in the exit channel was described by employing a two-effective centerapproximation (TEC). It was shown that, in spite of the noticeable asymmetry of the target electron cloud, fingerprints of coherent electron emission from the vicinities of the molecular nuclei appear in the electron emission spectra.We show here that interferences are still visible even after averaging the ionization cross sections over all the molecular orientations [5]. A comparison with results obtained forionization of H2 targets shows that the interference patterns corresponding to the heteronuclear case are less pronounced than for the homonuclear one. The origin of this behaviour can be attributed to the partial localization of the electrons around the alpha particle of the HeH+ molecular ion.[1] H. D. Cohen and U. Fano, Phys. Rev. 150, 30 (1966).[2] N. Stolterfoht et al., Phys. Rev. Lett. 87, 023201 (2001).[3] C. A. Tachino et al., J. Phys. B 42, 075203 (2009).