A study of gamma-ray spectra of thermal neutron capture in 143Nd and 145Nd; Including directional anisotropy and linear polarization measurements of such gamma rays from aligned 143Nd nuclei

Abstract

Abstract The γ-ray spectra following thermal neutron capture in 143 Nd and 145 Nd have been investigated with a 5-cc Ge(Li) detector. Samples enriched in 143 Nd and 145 Nd have been used. Energies and intensities of several transitions are given. The anisotropy of the directional distribution of neutron-capture γ rays from aligned 143 Nd nuclei has been measured. The degree of linear polarization of the 814 and 864 keV transitions in 144 Nd have been determined by using a Compton polarimeter. The E2 transitions of 616 and 696 keV were used for calibrating the efficiency of the polarimeter. The spins of the levels at 1560, 2292, 2377 and 2862 keV were determined from the anisotropy measurements. They are 2, 4, 2 and 2 respectively. The spins of the levels at 3027 and 3137 keV are very likely 4 and 3 respectively. The anisotropy and linear polarization measurements indicate that the 814 keV transition has an E1 character, while the 864 keV γ radiation is mainly an M1 transition with 18–38% admixture of E2. A compilation of E2-M1 mixing ratios for 2 + → 2 + transitions for nuclei with 18 ⩽ A ⩽ 212 is given.