K+, Na+, and Li+ Desorption from Oxygenated Tungsten

Abstract

The desorption times for K⁺, Na⁺, and Li⁺ from continuously oxygenated tungsten have been measured in the 1000–1500°K temperature range using an ac modulation technique. Under conditions of low alkali‐metal coverage on the surface, the experimentally derived values of desorption energy $\mathrm{(l)}$ and zero intercept ${\mathrm{(\tau }}_0)$ in the Arrhenius expression ${\mathrm{\tau \hspace{0.17em}=\hspace{0.17em}\tau }}_0\exp \mathrm{(l\hspace{0.17em}/\hspace{0.17em}kT)}$ sec are $${\mathrm{K}}^{+}\text{: l\hspace{0.17em}=\hspace{0.17em}1.5}\mathrm{eV}{\mathrm{;\; \tau }}_0{\text{\hspace{0.17em}=\hspace{0.17em}2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−10}}\sec ,$$ $${\mathrm{Na}}^{+}\text{: l\hspace{0.17em}=\hspace{0.17em}1.6}\mathrm{eV}{\mathrm{;\; \tau }}_0{\text{\hspace{0.17em}=\hspace{0.17em}7\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−10}}\sec ,$$ $${\mathrm{Li}}^{+}\text{: l\hspace{0.17em}=\hspace{0.17em}2.2}\mathrm{eV}{\mathrm{;\; \tau }}_0{\text{\hspace{0.17em}=\hspace{0.17em}2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−10}}\sec .$$ Alteractions of the surface using an oxygen spray produced noticeable effects, particularly for K⁺.