No abstract

No abstract

High-spin states in 2~were populated in the 2~ 4n) reaction using e-particles in the energy region 42-51 MeV. Prompt and delayed y-rays as well as conversion electrons were studied in addition to excitation functions, angular distributions and 7-7 coincidences. In this way a stretched cascade of y-rays from a level at 8125.9 keV was found to feed the previously known isomeric 9-level at 2185.7 keV. Spins and parities were established for levels up to and including a 19-level at 6098.0 keV. The levels with J== 17-and 19-at excitation energies of 5664.3 and 6098.0 keV are likely to be due to the simple p~/1 i~z and f5721 ii-~2 configurations. The agreement between calculated and experimental energies for all observed levels in the region J=9-19 is very good in cases where the empirical two-particle interactions used are satisfactorily well known. Above the 19-level there are three weakly populated levels at 7402.1, 7849.2 and 8125.9 keV, which are likely to have J > 20. None of these energies agrees with the calculated value 7695 +20 keV for the 20 + state of the ila~2 configuration which has the highest angular momentum produced by the four valence neutron holes. This apparent anomaly can be understood if the yrast levels with J > 20 have angular momentum contribution from the core. It seems likely that the states at 7402.1, 7849.2 and 8125.9 keV are due to proton core excited states of the type Irh9/2 h11~/zXVp~/2 i1~/2 with J==20 + and J==21 + and =h9/2 h;11/2 x vpT/1 f57~ i~32/2 with J==22 + or 23 +, respectively. The state at 8126keV has the highest energy so far directly observed in a stretched cascade of y-rays from the decay of a heavy nucleus produced in (e, x n) reactions.

Yrast excitations in the Nϭ82 isotone 137 Cs have been identified for the first time in thick-target ␥-ray coincidence measurements for the system 232 Thϩ 136 Xe using the Gammasphere array. The 137 Cs nuclei were produced in deep inelastic one-proton-transfer reactions. By-products of the main investigation were two well-developed rotational bands which were identified in heavy reaction partner products complementary to 137 Cs and are tentatively assigned to the little studied nucleus 231 Ac. There was no difficulty in placing the 11 observed 137 Cs transitions in a yrast level scheme extending to an I ϭ(31/2 Ϫ ) level at 5494 keV. Interpretation was also straightforward, since the experimental level energies are in close agreement with results of shell model calculations performed earlier using empirical single particle energies and interaction matrix elements derived from experimental data for other Nϭ82 isotones. ͓S0556-2813͑99͒00706-2͔