Absolute total and partial cross sections for ionization of nucleobases by proton impact in the Bragg peak velocity range

We present experimental results for proton ionization of nucleobases (adenine, cytosine, thymine, and uracil) based on an event-by-event analysis of the different ions produced combined with an absolute target density determination. We are able to disentangle in detail the various proton ionization channels from mass-analyzed product ion signals in coincidence with the charge-analyzed projectile. In addition we are able to determine a complete set of cross sections for the ionization of these molecular targets by 20-150 keV protons including the total and partial cross sections and the direct-ionization and electron-capture cross sections.