J. Dryzek, THE OPTICAL-POTENTIAL RESPONSIBLE FOR THE ABSORPTION OF A POSITRON ATA VACANCY, Journal of physics. Condensed matter, 9(38), 1997, pp. 8161-8168
We describe an approach to the positron trapping at vacancies based on
the optical theorem. We calculate the imaginary part of the optical p
otential in an ab initio model at the time when electron-hole excitati
on takes place. The obtained analytical formulae for the optical poten
tial are tested as a function of the positron incident energy, the pos
itron binding energy, and the electron density parameter r(s). The cal
culation of the optical potential range agrees well with the vacancy r
adius. The approach is used for the description of observed temperatur
e dependences of trapping rate at vacancies in pure metals as reported
in the literature. The results are satisfactory and the obtained valu
es of the optical potential are quite reasonable.