Image Charge Correction Parameter

The calculations of Voit and Biittner /55/ are based on the experimental a(T) data presented above /20/. They make no assumption on the barrier cross section. By assuming e = 2.5, they obtain from the data of the freshly-prepared sample I (table 1) values of Vq = 265 eV, w = 0.015 nm and A = 6.5 10 nm2, data which do not appear to be physically reasonable. 

It could be argued that e is the dielectric constant within the barrier, a value which cannot be determined directly, and that it cannot be excluded that e has values which are by far larger than 1. On the other hand, the above values differ from physically reasonable values by orders of magnitude and a value of about 100 would be necessary for e in order to obtain plausible values for Vq and w. e values of the order of 100, however can hardly be imagined within a potential barrier which is not even likely to contain strong permanent electrical dipoles. 

---