Beta-Gamma Directional Correlation inRe188

Abstract

These two effects tend to compensate each other in cases where the spin of the bombarded nucleus is large.A complete expression for magnetic scattering by finite-size nuclei with a magnetic momentum was derived by Walecka and Pratt 8 ; the connection with Rosenbluth's formula is discussed there.From Fig. 5 it is seen that for light elements, where magnetic scattering is big and thus our error (due to subtracting the : charge cross section) is small, the experimental points follow the theory quite closely. 5 B 10 seems to be the only exception. Since it has a large spin, this might be due to contributions of higher multipoles which are not present in 5 B n . For heavier nuclei the errors are large, and there seem to be no major conflicts between theory and experiment. The H theoretical point is higher than the experimental because no recoil is assumed in formula (4) which makes an appreciable effect only in H, and removes completely the discrepancy when taken into account.For the case of Li 7 a calculation of the scattering cross section was made by Willey, 9 using known wave functions for the ground state of Li 7 . The calculations were made for a LS coupling and for an odd-proton model. J. D. Walecka and R. H. Pratt (private communication). R. Willey (private communication). EXPERIMENTAL PROCEDURE AND RESULTST HE 17-h Re 188 was purchased from the Oak Ridge National Laboratory as processed, high specific activity (^20 mC/ml) 91-h Re 186 . At the time of assay before leaving Oak Ridge the Re 188 activity was approximately one-third of the total activity. Sources were prepared by evaporation of the nitric acid solution of the HRe04 on 0.25-mil Mylar backing. The sources were transparent. They were grounded by a thin f Supported in part by a grant from the National Science Foundation (G6337).The results are listed below for 41.5 MeV:LS model 3.70 X 10~3 2 cm 2 /sr; Odd-proton model, 5,71X10 -32 cm 2 /sr; Formula (4), 7.1X10" 32 cm 2 /sr; Experiment, 5.6X10 -32 cm 2 /sr.Although the magnetic moment in Li 7 is in agreement with the predictions of the LS model, the old proton model is considerably better than the LS model in predicing the scattering results. The case of He 4 is very special because the absence of magnetic scattering can yield information on an electric dipole moment of the electron. It will be discussed in another publication. 10 Further work on the lighter nuclei with higher electron energies would be very interesting because of the expected sharp decrease in cross section due to the effect of the magnetic form factors.