Search

A study of the beta decay of neutron rich nuclides of the A=147 chain is carried out at the TRIST

The $beta$ decay of $^{148}$La to levels in $^{148}$Ce has been studied at the TRISTAN ISOL facility at Brookhaven National Laboratory's High Flux Beam Reactor. A level scheme for $^{148}$Ce is presented which identifies a first excited 0$^{+}$ state at 770.16 KeV. 0$^{+}$, 2$^{+}$ and 4$^{+}$ members of the ground state band, as well as 0$^{+}_{\beta}$, 2$^{+}_{\beta}$, 4$^{+}_{\beta}$, 2$^{+}_{\gamma}$, 3^${+}_{\gamma}$ and the 1$^{-}$ and 3$^{-}$ members of an octupole band are identified. IBA-2 calculations for the N = 90 isotones and Z = 58 isotopes are presented.

The decays of the neutron-rich nuclides /sup 142/La, /sup 144/La, /sup 146/La and /sup 148/La to the levels of the transitional nuclides /sup 142/Ce, /sup 114/Ce, /sup 146/Ce and /sup 148/Ce, respectively, have been studied using mass-separated sources. Angular correlation studies have been employed to identify new excited 0/sup +/ levels in /sup 146 /Ce and support spin and parity assignments for 1/sup -/, 3/sup -/, 2 /sup +/, 3/sup +/, 4/sup +/ and 6/sup +/ levels in /sup 144/Ce and /sup 146/Ce. An excited 0/sup +/ level in /sup 148/Ce is indicated by coincidence ratios and electron studies, while no clear evidence can be found for the location of an excited 0/sup +/ level below 2 MeV in /sup 144/Ce. The resulting isotonic and isotopic systematics are discussed in terms of the transition from the closed shells at N=82 and Z=50 to the region of deformed nuclides. (13 refs).

Beta-ray end-point energies for Rb fission products were measured at the TRIST

An investigation of the level structure of /sup 146/Ce following the beta decay of the low-spin isomer of /sup 146/La has been carried out at the ISOL facility TRISTRAN. The half-life for the low spin isomer is found to be 6.0+or-0.4s. A partial level scheme for /sup 146/Ce below 2 MeV is given. The level energies and some B(E2) values extracted from the data have been compared with IBA-2 calculations done entirely with extrapolated parameters from neighboring Z nuclei in order to check the predictive power of the model. Systematics of the Z=58 isotopes and N=88 isotones indicate that although /sup 146/Ce is more deformed than its isotones with z>or=60, the transition to the well-deformed region can probably more correctly be thought to occur after /sup 146/Ce, between N=88 and N=90, as it does for Z>or=60. The abrupt onset of deformation present in the higher Z isotopes is not seen in the Ce isotopes where the trend is found to be rather smooth throughout. (17 refs).