Positive and Negative Self-Surface Ionization of Tungsten and Rhenium

Abstract

The self‐surface ionization of tungsten and rhenium has been investigated with a specially designed mass spectrometer. It has been found that both positive and negative singly charged atomic ions sublime from these metal surfaces in the 1900°—2600°K temperature range. The assumption that these processes can be described by a generalized Saha—Langmuir equation has been shown to be valid. The energies required for positive‐ion sublimation were found to be 12.1 and 10.7 eV for tungsten and rhenium, respectively. The negative‐ion sublimation energy for rhenium was determined as 12.6 eV and that for tungsten is given by approximately the same value. At 2300°K, the ratio of positive to negative ions evaporating from these surfaces was found to be about 40 for tungsten and about 20 000 for rhenium. These results are consistent with the following estimates for the electron affinities: A(W)=0.50±0.30 eV and A(Re)=0.15±0.10 eV.