Low-energy absolute pair-production cross-section measurements in targets of Z = 13, 26, 29, 50, and 82

Absolute cross sections for pair production by photons incident on targets of aluminum, iron, copper, tin, and lead were measured using the internal-source method. The measurements were made for the 1.119- and 2.6145-MeV ..gamma.. rays in the decays of /sup 46/Sc and /sup 228/Th, respectively, and also a composite cross section was measured for the mixture of the 1.1732- and 1.3325-MeV ..gamma.. rays in the decay of /sup 60/Co. The results are in general agreement with the theoretical predictions of Overbo and those of Tseng and Pratt, and clearly demonstrate the importance of accounting for electron screening of the nuclear Coulomb potential in the calculations.