The decay of 140La to levels in 140Ce

Abstract

The decay of 140La to levels in 140Ce has been studied with Ge(Li) spectrometers and [gamma]-[gamma] coincidence techniques. Precision energy and intensity values for 25 [gamma]-rays are reported. These transitions have been incorporated into a consistent decay scheme which includes an intensity balance for each level. Using the present data and the recent conversion electron data of Karlsson et al., it was possible to determine multipolarities for most of the transitions. The excitation energies (keV), spins and parities proposed for the levels in 140Ce populated via the decay of 140La are 1596.6 (2+), 1903.5 (0+), 2083.6 (4+), 2108.2 (6+), 2348.4 (2+), 2350.2 (5-), 2412.4 (3+), 2464.4 (3-), 2481.3 (4+), 2516.1 (4+), 2521.8 (2+), 2547.5 (1,2+), 2899.7 (1,2+), 3118.3 (1,2+), 3319.7 (1,2+). The level at 2108.2 keV (6+) was deduced to be isomeric. The proposed level scheme is compared with the excitation spectrum observed in the 141Pr(d, 3He)140Ce reaction and two spectra calculated using the quasi-particle description of pairing correlations.