Invited talk: Interference and non-Franck-Condon effects in ionization of H2 molecules by photon impact

FOJÓN O A

Conferencia; MPS 2010; 2010

Invited talk:Interference effects in photoionization of diatomic moleculesfirst predicted by Cohen and Fano [1] in the sixties are nowadays an active research area [2] including impact of photons[3], heavy ions [4] as well as electrons [5]. However, only recently the predicted interference patterns in the ejected electron spectra, analogous in some way to the Young´s double slit experiment, were detected in experiments with heavy ions [4]. These effects are not only of academic interest but also useful for the future development of molecular interferometry allowing to follow the steps of chemical reactions [6]. In this talk, we present recent results on interference effects by electron and photon impact on hydrogenmolecules. In the case of electron impact, multiple differential crosssections are obtained with a first order model for high enough incidentenergies and it is shown for the first time that interferences may be traced even in the single differential cross sections and also by means ofadequate asymmetry parameters. Moreover, comparison with recentexperiments is given [7]. We also present results of photoionization byphotons of a few hundreds eV. Bound and continuum states are accurately evaluated including electronic correlation by using B-spline basis functions [8]. Results are obtained for fixed-in-space hydrogen molecules and striking features are observed when the molecular orientation is parallel to the (linear) polarization of the incident photons: interference effects lead to the appearance of minima in the partial cross sections determined by the simple formula: k R = l π with k the ejected electron momentum, R the intermolecular distance and l the angular momentum of the partial cross section [9]. For perpendicular orientation, patterns similar to the ones of the Young´s experiment are observed. In addition, it is found that the vibrational distribution of the residualtarget does not follow the usual Franck- Condon behavior in the case of parallel molecular orientation. Such anomalies are related to  interferences [10].References1. H. D. Cohen and U. Fano, Phys. Rev., 150, 30 (1966).2. D. Akoury et al., Science, 318, 949 (2007).3. O. A. Fojón, J. Fernández, A. Palacios, R. D. Rivarola and F. Martín, J. Phys. B: At. Mol. Opt. Phys., 37, 3035 (2004).4. N. Stolterfoht et al, Phys. Rev. Lett., 87 023201 (2001).5. C.R. Stia, O.A. Fojón, P.F. Weck, J. Hanssen and R.D. Rivarola, J. Phys. B: At. Mol. Opt. Phys., 36, L257 (2003).6. Andrei Sanov et al., Science, 315, 610 (2007).7. Shyamal Chatterjee, D. Misra, A. H. Kelkar, Lokesh C. Tribedi, C. R. Stia, O. A. Fojón, and R. D. Rivarola, Phys. Rev. A, 78, 052701 (2008); S Chatterjee, S Kasthurirangan, A H Kelkar, C R Stia, O A Fojón, R D Rivarola and L C Tribedi, J. Phys. B: At. Mol. Opt. Phys., 42, 065201 (2009).8. F. Martín, J. Phys. B: At. Mol. Opt. Phys., 32, R197 (1999).9. J. Fernández, O. A. Fojón, A. Palacios and F. Martín, Phys. Rev. Lett., 98, 043005 (2007).10. J. Fernández, O. Fojón and F. Martín, Phys. Rev. A, 79, 023420 (2009).