Coincidence and directional correlation measurements on the decay of 156Tb(5.3 d)

Abstract

Coincidence and γ-γ directional correlation measurements on the decay of 156Tb to levels in 156Gd were carried out gating with 2 mm or 5 mm Ge(Li) detectors and displaying the spectrum of a 7.6 cm × 7.6 cm NaI detector. The dipole-quadrupole mixtures were determined for transitions of 262, 534, 960, 1065, 1066, 1159, 1222, 1333, 1644 and 1844 keV depopulating intrinsic levels above 1.5 MeV as well as levels at 1154, 1249 and 1355 keV in the gamma-vibrational band. The energies and intensities of previously unobserved transitions of 579.3, 690, 747, 805, 855, 1129, 1188, 1228, 1240, 1265, 1814, 1885, 1889 and 2047 keV were measured using Ge(Li) detectors. The available internal conversion electron data were used in conjunction with our photon data to calculate internal conversion coefficients. Branching ratios for E2 transitions de-exciting levels in the gamma band and E1 transitions de-exciting the negative parity states were calculated and compared with theoretical estimates. A revised decay scheme is presented.