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Ultra fast H+ Desorption from an Isolated NH3 Monolayer Adsorbed on a Xe Film Induced by a Resonant Core Electron Transition Studied by Auger Electron-Photoion Coincidence Spectroscopy

Mechanism of ion desorption from an isolated NH3 monolayer adsorbed on a Xe film (NH3/Xe) induced by a resonant core electron excitation is studied using Auger electron-photoion coincidence (AEPICO) spectroscopy. The total ion yield spectrum of NH3/Xe exhibits a threshold peak at the resonant excitation from N 1s to the 4a1 N-H antibonding orbital. The Auger electron spectrum of the isolated NH3 at the 4a1←N 1s resonant transition is found to be mainly due to spectator-Auger transitions. A series of AEPICO spectra at the 4a1←N 1s resonance is measured for the electron kinetic energies corresponding to the spectator Auger transitions. The AEPICO spectra show that H+ is the only desorbed ion species. The electron kinetic energy dependence of the H+ AEPICO yield displays a structure similar to that of the spectator-Auger electron spectrum. This result indicates that the H+ desorption probabilities are independent of the final states of spectator-Auger transitions. Based on these results, we suggest that the repulsive potential surface of the (N 1s)-1(4a1)1 state is responsible for the H+ desorption, that is, ultrafast H+ desorption mechanism is favorable in this system.