Analytical Sciences

In situ Measurements of the Desorption of Water from a TiO₂ Surface under Dry Air by Collecting the Photoemission Yield with an Open Counter

Daisuke YAMASHITA,* Atsushi ISHIZAKI,* and Tomoyuki YAMAMOTO**,***

*Research and Development Department, Riken Keiki Co., Ltd., 2-7-6 Azusawa, Itabashi, Tokyo 174-8744, Japan
**Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
***Institute of Condensed-Matter Science, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan

We investigated the desorption of water from a TiO₂ surface under a dry atmosphere by collecting the photoemission yield spectra with an open counter. For this purpose, a new attachment for the photoemission yield measurement was prepared. This apparatus is capable of detecting, in the open air, low-energy electrons excited by photons under dried atmospheres; the dew point is below −35°C. A significant change in the photoemission yield spectra due to exposure to a dry atmosphere was observed. To gain a better understanding of these results, observations of the change in the photoemission yield spectra caused by the thermal desorption of adsorbed water were also carried out. The results are consistent with those obtained by exposure to a dry atmosphere. Based on the relationship between the photoemission yield and the thickness of the water layer, the time dependence of the change in the thickness was explained by the second-order reaction rate equation.

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