Absolute doubly differential cross sections for ionization of adenine by 1.0-MeV protons

Double-differential ionization cross sections of adenine (C₅H₅N₅) by 1.0-MeV protons have been measured using a vapor-phase adenine target. Ejected electrons were analyzed by a 45^∘ parallel-plate electrostatic spectrometer in an electron energy range from 1 to 1000 eV at electron emission angles from 15^∘ to 165^∘. The effective target thickness of adenine was determined by a Rutherford forward scattering method and a vapor deposition method. Present data are in good agreement with recent calculations. Comparisons were made with other data on various hydrocarbon molecules. It was found that the ionization cross sections of these molecules can be scaled fairly well in terms of the total number of valence electrons.