The influence of subsurface species on desorption kinetics : 18O2/Zr(0001)

Isotopic oxygen (18O2) adsorption on Zr(0001) surfaces at 185 K is investigated with Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and temperature programmed desorption (TPD). The surface region of zirconium is saturated by low exposures of oxygen as determined by AES and LEED. However, as the exposure increases, thermal desorption features of H2 18O (20 amu) and H2 16O (18 amu) grow, with more H216O than H218O desorbing after isotopic oxygen exposure. These results indicate that significant kinetic mixing of surface and subsurface oxygen species as well as hydrogen transport from the bulk is involved in water production by this surface during heating.