Reactive scattering of NH3+ (v, J) ions at film covered indium tin oxide (ITO) surfaces

We describe the setup of an experiment for the investigation of ion-surface reactions with time of flight analysis of products. It consists of an ion source where state-selected ammonia ions NH3+ (v, J) are formed by resonance enhanced multi-photon ionization ((2 + 1) REMPI). The ions are guided to a scattering chamber where the interaction with an indium tin oxide (ITO) surface covered by a layer of H-atoms containing neutral molecules can be investigated as a function of the kinetic energy. Product yields are analyzed in a time of flight mass spectrometer (TOF). The characteristics of the experiment are illustrated by the help of SIMION trajectory calculations. We show that at impact energies around 15 eV pick up of H atoms from the layer occurs. At higher impact energies, around 30 eV, dissociative scattering of ammonia ions dominates. Collision energy resolved mass spectra (CERMS) are presented. The TOF analysis indicates an ammonia molecular layer as the origin for H abstraction in accordance with the experimental conditions.