Resonance behavior of internal conversion coefficients at lowγ-ray energy

Abstract

A resonance-like structure of internal conversion coefficients (ICCs) at low $\ensuremath{\gamma}$-ray energy ($\ensuremath{\lesssim}$100 keV) is studied. Our calculations revealed new, previously unknown resonance minima in the energy dependence of ICCs for the $\mathit{ns}$ shells at $E2$--$E5$ transitions. The resonances are the most defined for ICCs in light and medium elements with $Z\ensuremath{\lesssim}$ 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 $\mathit{ns}$ shells with $n\ensuremath{\geqslant}2$ as well as for the $\mathit{np}$ shells with $n\ensuremath{\geqslant}3$ and the $\mathit{nd}$ shells with $n\ensuremath{\geqslant}4$ 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.