STRUCTURE OF THE LOW-LYING ENERGY-LEVELS IN RE-187

Gamma radiations and conversion electrons in the decay of 23.9 h 187W to 187Re have been investigated using Ge(Li) detectors and a Si(Li)-Ge(Li) conversion electron spectrometer. Forty-one γ-ray lines are observed, including seven new lines. Gamma-gamma angular correlations of the 551.57-134.25, 479.56-72.02, 479.56-(72.02)-134.25, 72.02-134.25 and 246.33-618.35 keV cascades have been measured. From the measurements of the conversion coefficients and the γ-γ angular correlations, the E2/M1 mixing ratios were determined as δ(134.25) = 0.184 ± 0.003, δ(238.82) < |0.9|, -2.0 < δ(246.33) < -0.2, δ(589.12) = |0.58+∞-0.58|, -1.5 〈 δ(618.35)-0.4 and δ(772.85) = |0.41+0.28-0.41|. Theoretical calculations based on the Nilsson model in which Coriolis coupling and quasiparticle-phonon and rotation-vibration interactions are taken into consideration have been performed. The low-lying levels could be assigned to the Nilsson states mixed with the quadrupole vibrations: β vibration (K = Ω) and γ± vibration (K = Ω ± 2). Good agreement between experimental and calculated energy levels was obtained and the calculated mixing ratios were consistent with experimental results. © 1979.