Positive and Negative Ion Sublimation from Transition Metal Surfaces: A Review of Some Recent Results

Singly charged, positive and negative, atomic ions have been observed to sublime freely from 4d and 5d transition metal surfaces in the 1800 to 2600 K temperature range. The rates of sublimation were found to be about equal to those which would be observed under conditions of thermal equilibrium. Ion sublimation energies were obtained from the temperature dependence of these sublimation rates. The energies were found to be consistent with currently accepted values for the atom sublimation energy, electron work function, and first ionization potentials of the elements investigated. The electron affinities of these metal, atoms were determined from an isothermal measurement of the ratio of positive to negative ion sublimation rates. The results were compared with some recent theoretical estimates of this quantity for those 3d transition metals whose valence electron configurations are analogous to the 4d and 5d elements considered here.