Metastable Atoms and Molecules. III. Metastable Impacts on Surfaces with Various Work Functions

Abstract

Surfaces of atomically clean tungsten, with work function 4.5 eV, tungsten oxidized with a monolayer of oxide and having a work function 6.6 eV, and tungsten coated with BaO with a work function probably under 2 eV were hit by metastable atoms or molecules of Ar, Xe, ${\mathrm{N}}_2$, and ${\mathrm{H}}_2$. The emission of secondary electrons by metastable atoms and the surface ionization of the atomic metastables were shown to follow the expected dependency on the work function. The ${\mathrm{N}}_2$ molecular metastables were weakly surface ionized as ${\mathrm{N}}_2^{+}$ on the oxidized tungsten but not on the surfaces of lower work function. Secondary electron emission either did not occur at all or was obscured by the large emission of C${\mathrm{N}}^{-}$ negative ions. No C${\mathrm{N}}^{-}$ emission nor electron emission was observed on the W-O surface. Metastables of ${\mathrm{H}}_2$ dissociated on the clean and the oxidized surfaces. On the clean surface, one atom became $\mathrm{H}\mathrm{}\left(2p\right)\mathrm{}$ and gave out Lyman alpha radiation. On the W-O surface, one of the H atoms became a proton and no Lyman alpha radiation was produced. No other ion emission than ${\mathrm{H}}^{+}$ occurred.