Surface Penning

Penning ionization is a dominant reaction when nitrogen or neon is used in the DART source. Nitrogen or neon ions are effectively removed by electrostatic lenses and are not observed in the background mass spectrum. When helium is used, the dominant positive-ion formation mechanism involves the formation of ionized water clusters followed by proton transfer reactions. Negative-ion formation occurs by production of electrons by Penning ionization or by surface Penning ionization ... [Pg.49]

Negative ions can be formed by electron capture due to the presence of thermalized electrons produced by Penning ionization or by surface Penning ionization. Negative ions can also be obtained by reactions of analyte molecules with negative ions formed from atmospheric water and oxygen to produce the deprotonated molecule. [Pg.64]

SPI Surface Penning Ionization Neutral atoms, usually He, in excited states are incident on a surface at thermal energies. A surface electron may tunnel into the unoccupied electronic level, causing the incident atom to become ionized and eject an electron, which is then detected. This technique measures the density of states near the Fermi-level, and is highly surface sensitive. [Pg.21]

Ultra-violet photoemission spectroscopy (UPS) probes the density of states, and ion neutralization spectroscopy (INS) and surface Penning ionization (SPI) provide similar information with probes of ions and metastable atoms, respectively. Angle-resolved UPS can determine the valence band structure. X-ray Photoelectron Spectroscopy (XPS) provides information on chemical shifts of the atomic core levels, and this can also help in understanding chemical bonding at the surface. [Pg.36]

SPiES Surface Penning ionization Eiectron Spectroscopy... [Pg.1088]

SPIES Surface Penning ionization electron spectroscopy... [Pg.25]