EXPERIMENTAL AND THEORETICAL STUDY OF ORIENTATION EFFECTS IN H++He IONIZATION

D. FREGENAL; R. O. BARRACHINA; G. BERNARDI; R. DELLA PICCA; P. FOCKE; S.G. SUÁREZ; J. FIOL

Salamanca

Conferencia; 10th European Conference on Atoms Molecules and Photons; 2010

European Physical Society

Recent experimental and theoretical results have disclosed evidence of anomalies in the ionization cross sections of atoms and molecules by positron impact. Experimental fully-dierential cross sections revealed a displacement of the well known Electron-Capture-to-the-Continuum (ECC) cusp from its theoretical position. Recent Classical-Trajectory Monte-Carlo calculations have related this result to a strong alignment of the electron-positron pair in the nal state. These results have motivated us to investigate the appearance of similar alignment eects in atomic ionization by collisions with ions. In this communication we present measurements and calculations of ionization dierential cross sections in H++He in the range (20-50 keV/amu). Present results show that the alignment phenomena in ion-atom collisions is as strong as the observed with positrons. This effect is illustrated in the electron momentum distribution, in the vicinity of the ECC cusp, of Fig. 1 for helium ionization by impact of protons at E = 20 keV/amu.