氧的同位素气体在NiO表面的热脱附的测定与分析

Desorption of Gases Containing Oxygen Isotopes from NiO Surfaces

采用程序升温脱附实验方法测量氧的同位素C16O2,C18O2和18O2分别在Ni16O表面吸附后的脱附谱,其结果表明C16O2在Ni16O表面吸附后出现C16O2和C16O两个波峰,且C16O2和C16O的脱附量随C16O2气体暴露量增加而增加,其峰值温度随C16O2气体暴露量增加而减少,当C16O2气体覆盖度超过一定值后,C16O2和C16O脱附量趋于常数,其活化能分别是0.48 eV和0.42 eV。C18O2在Ni16O表面吸附后出现C16O2,C18O16O,C18O2三个波峰,这说明吸附气体C18O2与Ni16O表面发生氧同位素交换,随温度升高而脱附出C16O2;18O2在NiO表面吸附后主要以18O2脱附,说明了富18O2有相对抑制与Ni16O表面氧的同位素交换的作用。

The desorption spectra of oxygen isotopes in gases of C^16O2, C^18O2, and ^18O2 from the Ni^16O grain surfaces were systematically studied with temperature progrmmned desorption （TPD）, respectively. Two desorption peaks, correspending to C^16O2, and C^16O, respectively, were observed; and as the C^16O2 exposure increased, the desorption rates of C^16 O2,and C^16O increased,but their peak temperatures decreased. At a coverage of C^16O2 on the Ni^16O surfaces higher than the critical value,the desorption rates of C^16O2,and C^16O with the activation energies of 0.48 eV and 0.42 eV, respectively, remained unchanged. The three distinctive desorption peaks （ C^16O2, C^18O^16O, and C^18O2）, originated from adsorption of C^18O2 on the Ni^16O surfaces show that the exchange of the ^16O and ^18O isotopes occurs on the Ni^16O surfaces;and as the temperature increases,the desorption of C^16O2 dominated. The fact that most desorbed gas,from the Ni^16O surfaces heavily covered with ^18O2, was found to be ^18O2 indicates that the excess ^18O2 inhabits the exchange of oxygen isotopes on the Ni^16O surfaces.