K internal conversion near threshold and some nuclear structure studies in the rare earth region using radioactive decay and reactions

A study of K internal conversion near threshold is presented. The XPG technique was employed with Si(Li) detectors being used to obtain singles and coincidence spectra. Five transitions were studied, none of which had an energy that exceeded the K binding energy by more than 4 keV. The α/sub K/ values obtained are 1.02 +- 0.15 (63.1 keV E1 in 169Tm), 0.75 +- 0.05 (72.0 keV E1 in 187Re), 10.25 +- 0.58 (67.1 keV M1 in 174Lu), 11.4 +- 0.67 (57.8 keV M1 in 162Ho), and 12.04 +- 0.07 (56.6 keV M1 in 164Ho). These results are compared to those of other workers, and to theoretical values. The (α,2n) reaction at 24 MeV was used to populate states in the gamma band of 166Er. Two new members, the 9+ and 10+ states of the gamma band are proposed at 1751.0 keV and 1964.3 keV respectively. E2/M1 admixtures in transitions depopulating the gamma band were derived from the gamma angular distributions, and are compared with results obtained from γ-γ angular correlations and Coulomb excitation measurements. The (7Li,α:2n) reaction was studied at energies between 24 and 32 MeV with some rare earth targets. Angular distributions of alpha particles and gamma-rays provide evidence for describing the reaction as one of cluster transfer at grazing incidence along a Coulomb trajectory. The deduced interaction radius is R/sub c/ equals 11.2 fm. The degree of alignment and the angular momentum transferred are discussed. A study of the decay of 156Tb, indicated that the 5 hr. and 24 hr. isomers decay independently to the ground state (5 d). The isomeric transition was not observed, but the experiment served to place either an upper limit of 15 keV on its energy or a lower limit of 500 ns on the half-life of the 49 keV state