Decay of¹⁵²Eu and the unified nuclear model

Summary  The radiations from152Eu (t1/2=13 yrs) were investigated using an intermediate image spectrometer, a magnetic thin lens spectrometer and a coincidence scintillation spectrometer. Three β--groups are present with end-points (1450±25), (1040 ±20), (710±20)keV; the highest energy group exhibits an α-shape. γ-ray investigations showed that the following γ-rays are present: 101 (5), 121 (88), 244 (30), 315 (4), 344 (100), 410 (9), 442 (4), 710 (13), 770 (77), 888 (14), 970 (89), 1090 (96), 1127 (96) and 1410 (135) keV.K-conversion coefficients were estimated for most of these transitions and multipole orders were assigned. X-ray-γ, γ-γ and β-γ coincidence experiments allow us to construct the decay scheme of152Eu. The difference in level structure in152Sm (N=90) and152Gd (N =88) is evident from the experimental results. The first three excited states at 121, 365 and 807 keV in152Sm are identified as the three members of the ground state rotational band (K=0) ; the levels at 1090 and 1248 keV havingI= 2 +, and 3 + respectively are shown to be the quadrupole γ-vibrational states corresponding to K=2. The highest excited state in152Sm is at 1417 keV and is most likely fed entirely byL-capture; this is the only odd-parity state in152Sm having the character I=1-. The levels in152Gd at 344 and 754 keV both with I=2 +, reached by β--decay, are characteristic of the collective vibrations of the electric quadrupole type about a spherical equilibrium shape. The level at 1114keV in152Gd has the character I=— and is interpreted as due to the octupole vibrations. The ground state of152Eu has been assigned the spin I=4 -; the branching ratios and the transition probabilities for the β--groups and electron capture transitions have been calculated. The experimental results are consistent with the predictions of the Unified Nuclear Model.