Nonresonance excitation of the nucleus in annihilation of positrons with K-shell electrons

A theoretical analysis is carried out of the nonresonance excitation of the nucleus in annihilation of positrons with emission of bremsstrahlung. The plane-wave approximation is used in calculation of the cross section. General formulas are obtained for ML and EL excitations of the nucleus. Specific calculations are carried out for the nuclear levels of the isotope 115In. The calculations take into account the distortion of the shape of the spectrum of incident positrons as a function of the thickness of the irradiated sample. It is shown that the role of the nonresonance mechanism for excitation of the nucleus is dominant. The results are consistent with existing experimental data