Bare-carbon-ion-impact electron emission from adenine molecules: Differential and total cross-section measurements

Double-differential ionization cross sections (DDCS) for bare-carbon-ion-induced ionization of vapor-phase adenine molecules (C5H5N5) have been measured. The experiment has been performed using an electron spectroscopy technique. Electrons ejected from adenine were analyzed by a hemispherical electrostatic deflection analyzer over an energy range of 1-450 eV for emission angles from 20 degrees to 160 degrees. The single-differential cross section (SDCS) and total ionization cross section were also deduced. The experimental results have been compared with the continuum distorted wave-eikonal initial-state model calculation. We have observed a very good agreement between the theory and experiment. The angular distribution of the DDCS, SDCS and the asymmetry parameter for low-energy (E-e <= 0.5 a.u.) electron display an oscillatory behavior which is in contrast to that observed in ion-atom collisions. A comparison is also made with available experimental cross-section results for uracil target colliding with the same velocity bare carbon ions and the scalability of ionization cross sections among these molecules is discussed.