Resonance behavior of internal conversion coefficients at low γ-ray energy

A resonance-like structure of internal conversion coefficients (ICCs) at low γ-ray energy (≲ 100 keV) is studied. Our calculations revealed new, previously unknown resonance minima in the energy dependence of ICCs for the ns shells at E2-E5 transitions. The resonances are the most defined for ICCs in light and medium elements with Z ≲ 50. It is shown that ICCs may have up to four resonances for outer shells while it has been assumed so far that only one resonance exists. Well-pronounced resonances in ICCs at E1 transition were discovered for the ns shells with n ≥ 2 as well as for the np shells with n ≥ 3 and the nd shells with n ≥ 4 of all elements up to superheavy ones. Simple expressions for approximate values of the E1 resonance energy were obtained which are of importance for determination of the resonance energy range where the interpolation of ICCs taken from tables or databases may give significant errors. The occurrence of resonances in ICCs is explained by vanishing conversion matrix elements under changes of sign. The peculiarities of the behavior of the matrix elements and electron wave functions at the resonance energy are considered. Available experimental ICCs for electric transitions with energies near the expected position of resonances satisfactory agree with our calculations.