Doubly differential distribution of electron emission in ionization of uracil in collisions with 3.5-MeV/u bare C ions
Résumé
We report the energy and angular distribution of the electron emission from an RNA base molecule uracil in collisions with 3.5-MeV/u bare C ions. The absolute double differential cross sections (DDCS) are measured for emission energy between a few to 600 eV. The angular distributions are compared to those obtained for the O2 molecule in the same experiment. The single differential cross sections (SDCS) are also deduced. The energy and angular distributions of the DDCS and SDCS are compared with the state-of-the-art quantum-mechanical models based on continuum distorted wave-eikonal initial state (CDW-EIS) and correct boundary first Born (CB1) approximations which use a suitable molecular wave function for uracil. The models, however, give substantial deviations from the observed energy and angular distributions of the DDCS as well as SDCS. The CDW-EIS calculations are closer to the data compared to the CB1. In the case of uracil a large difference in the forward-backward emission of electrons was observed in comparison to that in collisions with an oxygen molecule.