Angular Distribution of Gamma Rays from Coulomb Excitation

The angular distributions of gamma rays with respect to the incident proton beam on a thick target have been measured for gamma rays following Coulomb excitation in Pt194,196, Au¹⁹⁷, Ta¹⁸¹, Ag107,109, Pd¹⁰⁶, Pd¹⁰⁸, Pd¹¹⁰, and Rh¹⁰³. The observed angular distributions deviate considerably from the semiclassical theory of angular distributions of gamma rays following Coulomb excitation given by Alder and Winther. Empirical curves of energy-dependent coefficients a_ν(ξ) for a thick target are obtained from the results for Pt194,196 and Pd¹⁰⁶. With these empirical coefficients, information on the spin sequences and the character of the gamma transitions are deduced from the angular distribution measurements in the odd mass nuclei. The spin sequences are as follows: 7/2(E2)3/2 and 5/2(E2+M1)3/2 with δ_γ=-0.75 (where δ_γ²=E2/M1) for the 550- and 277-kev transitions, respectively, in Au¹⁹⁷; 11/2(E2)7/2 and 11/2(E2+M1)9/2 with δ_γ=0.51 for the 303- and 166-kev transitions, respectively, in Ta¹⁸¹; 5/2(E2)1/2 and 3/2(E2+M1)1/2 with δ_γ=-0.19 or -1.14 for the 427- and 325-kev transitions, respectively, in Ag107,109; and 5/2(E2)1/2 and 3/2(E2+M1)1/2 with δ_γ=-0.18 or -1.17 for the 365- and 305-kev transitions, respectively, in Rh¹⁰³.