Low-energy (5–80 eV) electron-stimulated desorption of H + (D +), OH + (OD +), O +, and NO + from solution-grown NaNO 3 crystals

Abstract

Low-energy (5–80 eV) electron-stimulated desorption of H + (D +), OH + (OD +), O +, and NO + from solution-grown NaNO 3 crystals is studied by quadrupole and time-of-flight mass spectrometry. Desorption yields and thresholds are reported as a function of incident electron energy and flux. The O + and NO + are degradation products of the NaNO 3 substrate, whereas the H + (D +) and OH + (OD +) ions arise primarily from -H(D) and/or -OH(OD) termination sites. The threshold energies indicate that degradation involves Auger-stimulated dissociation of the nitrate group. We associate the ∼24 eV threshold for H + (D +) desorption with intramolecular decay of a single hole in the O(2s) level of either NaOH(OD), or possibly HNO 3, terminal groups and the yield increase at ∼33 eV with intermolecular decay of the Na (2p→3s) exciton. We correlate the OH +(OD +), O + and NO + desorption thresholds at ∼33 eV primarily with excitation of the Na (2p→3s) exciton. Desorption of NO + and O + may also involve intramolecular Auger decay of holes in the 2e′ and/or 3a 1 ′ nitrate valence bands. The H + translational energy distributions peak at ∼5–7.5 eV, and H + dominates the cation desorption yields from solution grown NaNO 3 crystals by a factor of ∼100.