Absolute double differential ionization cross sections of gas-phase nucleobase molecules by 0.5- to 2.0-MeV protons

Abstract

We have measured absolute ionization cross sections of gas-phase adenine (C5H5N5) and uracil (C4H4N2O2) molecules bombarded by 0.5- to 2.0-MeV protons. Cross sections are given as functions of the energy and angle of ejected electrons. Ejected electrons with energies up to 1000eV were analyzed by a parallel plate electrostatic spectrometer. The angle of ejected electron ranges from 15 to 165 degrees with respect to the incident beam direction. Present data are compared with other data reported previously for various hydrocarbon molecules. We found that the cross sections divided by the number of weakly bound outer-shell electrons are nearly the same for these complex molecules irrespectively of the chemical structure of individual molecules.