Measurements of Gamma-Ray Absorption Coefficients

The absorption of -rays in Al, Cu, Sn, Ta, and Pb was measured using -rays from I^131, Cu^64, Mn^54, Co^60, Zn^65, and Na^24. Tests showed that scattering from nearby objects and from the absorber were negligible. Tests of the absorption of radium -rays in Pb showed good agreement with other workers and with theory. The absorption curves of I^131 showed the presence of a 0. 65-Mev -ray about 15 percent as abundant as the 0. 367-Mev -ray. Absorption coefficients measured with the other sources showed agreement within 0. 5 percent to 2 percent with theory. An anomalous absorption coefficient (5 percent less than expected) with tantalum absorber (Z=73) and Zn^65 and Co^60 sources (h1. 2 Mev) needs reinvestigation.