Anomalous Electric Dipole Conversion Coefficients in Odd-Mass Isotopes of the Heavy Elements

A detailed review is given of experimental data on the anomalous L- and M-shell conversion coefficients of low-energy electric dipole transitions observed in the decays of odd-A nuclei of high atomic number.The data are consistent in every case with the interpretation that the $E1$ conversion coefficients in the LIII shell agree with the theoretical, model-independent coefficients calculated by Sliv and Band and by Rose. It is definitely established in several well-measured cases that the LI and LII coefficients are substantially larger than the theoretical values. The most striking anomaly occurs in the 84.2-kev transition in Pa²³¹, where the LI and LII coefficients are 21 and 15 times larger than the theoretical values, respectively.The experimental LI and LII coefficients are correlated with the lifetimes of the transitions, and it is shown that the magnitude of the anomaly (LI plus LII) is proportional to the retardation in gamma-ray lifetime over that calculated from the single-proton formulas. No systematic trend has been observed in the deviations of the LI and LII coefficients individually.