Electron stimulated desorption ions of hydrogen and deuterium molecules in extremely high vacuum

Abstract

By using an ionization gauge with a large-angle ion deflector, we have measured electron stimulated desorption (ESD) ions emitted from the grid in extremely high vacuum. Combination of energy analysis with mass analysis makes it possible to detect molecular species of ESD ions and gas-phase ions separately. The observed ESD ions in this experiment originate from a small amount of adsorbates, ~ 10 −5 monolayer. The behavior of ESD ions of hydrogen and deuterium has been observed by introducing the deuterium (D 2) gas at 1.9 × 10 −9 Pa. The D 2 + ions have been detected in the ESD mass spectra, but no peak has appeared at mass number 3 (HD). The energy of the D 2 ESD ions is the same as that of H 2 ions, which is slightly higher than that of H ESD ions. Time dependence of the ESD intensity indicates the existence of several chemisorption sites of H 2 and/or D 2 molecules at room temperature.