Experimental studies of nuclear effects in internal conversion in Ta181 and Lu175 have been performed.Nuclear structure effects (“penetration” effects), in internal conversion are described in general.Calculation of theoretical conversion coefficients are outlined.Comparisons with the theoretical conversion coefficient tables of Rose and Sliv and Band are made.Discrepancies between our results and those of Rose and Sliv are noted.The theoretical conversion coefficients of Sliv and Band are in substantially better agreement with our results than are those of Rose.The ratio of the M1 penetration matrix element to the M1 gamma-ray matrix element, called λ, is equal to + 175 ± 25 for the 482 keV transition in Ta181 .The results for the 343 keV transition in Lu175 indicate that λmay be as large as – 8 ± 5.These transitions are discussed in terms of the unified collective model.Precision L subshell measurements in Tm169 (130keV), W182 (100 keV), and Ta181 (133 keV) show definite systematic deviations from the theoretical conversion coefficients.The possibility of explaining these deviations by penetration effects is investigated and is shown to be excluded.Other explanations of these anomalies are discussed.
