Single ionization of diatomic molecules due to the impact of fast proton beams is theoretically studied. The main interest is focussed on the analysis of the possible existence of interference patterns in the corresponding electron spectra due to coherent emission from the vicinities of the molecular centres. The case of N 2 targets is considered. A fully coplanar geometry in which the emitted electron, the incident particle and the molecule are all in the same plane is considered. The dynamics of the reaction is described within the continuum distorted wave-eikonal initial state model, and in the exit channel a two-effective centre approximation is employed. It is shown that fingerprints of coherent electron emission appear in the corresponding angular distributions. Also, double differential cross sections as a function of the energy and of the angle of the ionized electron, obtained by averaging the angular spectra over all molecular orientations, are calculated. Electron emission in opposite phases is found for the two inner 1sσ g -and 1sσ * u -orbitals, according with their gerade and ungerade character.
The doubly differential distributions of low-energy electron emission in the ionization of water molecules under the impact of fast bare oxygen ions with energy of 48 MeV are measured. The measured data are compared with two quantum-mechanical models, i.e. the post and prior versions of the continuum distorted wave-eikonal initial state (CDW-EIS) approximation, and the first-order Born approximation with initial and final wavefunctions verifying correct boundary conditions (CB1). An overall excellent qualitative agreement is found between the data and the CDW-EIS models whereas the CB1 model showed substantial deviation. However, the detailed angular distributions display some discrepancies with both CDW-EIS models. The single differential and total cross-sections exhibit good agreement with the CDW-EIS models. The present detailed data set could also be used as an input for modeling highly charged ion induced radiation damage in living tissues, whose most abundant component is water. Similar measurements are also carried out for a projectile energy of 60 MeV. However, since the double differential cross-section data show similar results the details are not provided here, except for the total ionization cross-sections results.
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