Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 8: Poster HU 1
A 8.26: Poster
Samstag, 5. März 2005, 08:30–18:30, Poster HU
High-Frequency Oscillations in Electron Emission Interferences from H2 — •John Tanis1, Sabbir Hossain1, and Nikolaus Stolterfoht2 — 1Western Michigan University, Kalamazoo, Michigan 49008 USA — 2Hahn-Meitner-Institut, D-14109 Berlin
High-frequency oscillations are observed in the electron emission spectra of H2 by 1-5 MeV H+ impact. These oscillations, which are superimposed on the primary and secondary interference structures observed previously, have a frequency significantly higher than those observed for the primary structures, and do not appear to vary with the electron observation angle or the collision velocity. A tentative explanation is proposed based on the fact that for H+ + H2 collisions the projectile and target centers are identical. It is postulated that the passing H+ ion in combination with a target center forms a transient molecule of large effective internuclear separation from which coherent electron emission takes place, with the consequence that oscillations occur for small intervals of the ejected electron velocity. In such a scenario, the resulting projectile-target two-center emission from the transient molecule gives rise to interference between the amplitude for direct ionization and that for ionization followed by postcollisional scattering in the field of the passing H+ ion. Furthermore, because electron emission occurs primarily at large impact parameters for the collision velocities considered here, an orientational effect might be expected due to the fact that ionization is most likely as the ion passes at its distance of closest approach, i.e., when the transient molecule is oriented with its internuclear axis perpendicular to the beam direction.