Studies of NO adsorption on proton-irradiated MgO surfaces

Abstract

Recently, adsorption studies of gases for various adsorbents have been intensive because they are useful in probing the fine structure of the surface. Meso-sized MgO(100) powder was irradiated by a proton beam with a high energy of 35 MeV. Transmission electron microscope (TEM) investigations revealed no structural change of the MgO powders after irradiating with the proton beam. After proton beam irradiation, NO gas isotherm adsorption data were recorded from the same sample below the triple point (109.8 K). The results revealed that there was no hint of multi-isotherm step formation, which indicates the creation of an atomic layer of NO molecules. Instead, only a monolayer of NO molecules was obtained. It is understood that pre-existing unwanted impurities, such as water and carbon-related organic gases, hinder the formation of atomic layers in a regular fashion on the MgO powder surface. By comparing NO adsorption data from the pure and the proton-irradiated MgO samples, we were able to calculate the surface-related thermodynamic characteristics, including the 2-dimensional compressibility and the heat of adsorption.