SURFACE-INDUCED ION NEUTRALIZATION WITH HIGH-ENERGY DEPOSITION

Ion-to-neutral conversion at surfaces is found to be complementary to what with gas-phase targets for neutralization-reionization mass spectrometry and to yield high-energy neutral species. With an Ag surface deposited on an in-line Si substrate, neutralization reionization efficiencies of 0.01% are achieved using 9.8 keV CH4+, with the neutral CH4 receiving a median internal energy of 14 eV; with a conventional target of K vapor, the efficiency is 0.4% with a neutral energy of 8.2 eV expected from their ionization energy difference. The energy deposition can be increased by increasing the potential that deflects ions into the surface; in this way approximately 15% of CH4 neutral species can be given > 20 eV of internal energy. Product abundances from CH4 dissociation provide a useful estimate of the distribution of energy values deposited in neutralization.