Abstract
Thermally stimulated exoelectron emissions (TSEE) from nickel and oxidized nickel surfaces after excitation by means of abrasion and X-ray irradiation in air were measured using a gas-flow type G-M counter equipped with the heating unit.
The results obtained are as follows:
(1) There were three remarkable peaks in the TSEE glow curves up to 400°C; at about 120°C (1 st), 230°C (2 nd) and 350°C (3 rd). No peak was observed in the second run of heating.
(2) The emission intensity was stronger in the samples excited by X-ray irradiation than in those excited by abrasion. A significant increase in emission intensity was obserbed with the samples excited by X-ray irradiation after abrasion.
(3) Oxidized nickel and nickel oxide powder without excitation showed the third peaks only.
(4) The emission intensity at the first and second peaks increased with the time of X-ray irradiation and eventually became constant.
(5) When nickel was irradiated by X-ray after being oxidized, the first and second peak intensities increased extremely with the oxidation temperature and hence with the amounts of surface oxide. Each of these intensities, however, showed a maximum value at a certain temperature of oxidation. It is suggested that although the exoelectron emission is caused by the surface oxide formed on nickel, the bulk oxide itself is not responsible for the emission.
(6) The ratio of the first to the second peak intensity was nearly constant, independent of both the oxidation temperature and the X-ray irradiation time. This fact suggests that there is a correlation between the origins of the first and second peaks of the exoelectron emission.
