Interference effects in single electron ionization of diatomic molecules by fast ion impact.

C.A TACHINO; M.E. GALASSI; F. MARTIN; R. RIVAROLA

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Conferencia; International conference on many particle spectroscopy of atoms, molecules, clusters and surfaces (MPS 2010); 2010

Since the decade of 1960, when pioneer investigations about the coherent electronemission from diatomic molecules were published, a great amount of experimental andtheoretical researchs related to interference effects have been carried out. The majority ofthese works were done considering simple molecular targets such as H2 +, H2 and D2 (see Ref. [1] for a brief review). There are a relatively scarce number of works that analyzethe presence of this effect in the electron spectra of more complicated molecules such as N2, O2, CO [2-4]. A main problem with these kind of targets is that they present several molecular orbitals (MO), and the electronic emission can occur from any of them. In consequence, theionization cross sections must be computed taking into account the partial contributions from eachMO. Moreover, each individual molecular orbital will present its own interference pattern.In [3] and [4], where single ionizaton of N2 and O2 molecules by ion impact was experimentally analyzed, the authors attributed the origin of the oscillations that appear in ionization crosssections to second-order effects related to intramolecular scattering. This conclusion is based on the analysis of the oscillation frequencies, which are in close agreement withthe ones characteristic of secondary interferences. According to these authors, noevidence of primary Young-type interferences appears.In the present investigation, we extend our previos works [5,6] to theoretically analyse thepossibility of the existence of interference patterns for diatomic molecules with more thanone molecular orbital in the fundamental state. The CDW-EIS model and a two-effective centerapproximation are employed to describe the dynamics of the reaction and the final state ofthe active electron in the continuum of the heavy particles, respectively. We consider a coplanargeometry where the emitted electron, the projectile and the molecule are all in the same plane. [1] H. D. Cohen and U. Fano, Phys. Rev. 150,30(1966). [2] R. D. Rivarola, Nucl. Instr. Methods B 261,161 (2007). [3] B. Zimmermann et al., Nature Physics 4, 649(2008). [4] R. Della Picca et al., Phys. Rev. A 79, 03270(2009). [5] C. A. Tachino et al., J. Phys. B 42, 075203(2009).