On field evaporation

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Abstract
The theory of field evaporation outlined in previous publications (Müller 1956, Gomer and Swanson 1963, Brandon 1965 a) has been extended to include the effects of image gas bombardment of the specimen and has been experimentally tested for the metals W, Mo and Pt in the range 60 to 90°K. In general the experimental results are consistent with the theory, polarization corrections amounting to some 15% of the total energy required to evaporate the doubly charged metal ions. The most serious discrepancies were observed in the case of molybdenum and are associated with plastic deformation occurring during the field evaporation process and with the presence of tightly bound non-metallic impurities. Deviations from the simple theory, in particular low pre-exponential factors in the rate equations, are associated with partial tunnelling of the metal ions through the activation energy barrier.