R. Menegazzo

Sum-up and pile-up contribution to cross-over peaks in coincidence γ spectroscopy

Abstract High-efficiency arrays for γ spectroscopy, now available in several Laboratories, make possible the measurement of very weak cross-over transitions of high potential interest. A limit to the measurement possibilities comes, however, from the simultaneous detection of two γ-rays of a stop-over cascade (or “sum-up”), which cannot be distinguished from the true detection of the cross-over transition. We propose a new method to measure (and correct for) the sum-up effect, which can be used with symmetric γ detector arrays (like GASP and GAMMASPHERE), and discuss the possible techniques for identifying and estimating quantitatively the contribution of random pile-up, which can be sizeable at high counting rate. These ideas have been experimented at GASP in a dedicated measurement with a radioactive source of 52 Mn . The results of this measurement are presented and discussed. Moreover, as a significant example, the method is applied to deduce the intensity of the E3 cross-over transition from the lowest 3− state of 148 Gd .

Search for hyperdeformed structures populated in the 37Cl+120Sn reaction by using EUROBALL III

Abstract: The ridge structure with ΔEγ=±30 keV, observed in the past in coincidence with protons emitted in the reaction 187 MeV 37Cl +120Sn and attributed to an hyperdeformed nuclear shape in 152Dy, has been studied in a new experiment performed with the EUROBALL III array. The ridge is now observed in coincidence with transitions in the yrast superdeformed band of 152Dy but no discrete rotational bands have been identified.

High-spin structure in

High-spin states of K-40 have been populated in the fusion-evaporation reaction C-12(Si-30,np)K-40 and studied by means of gamma-ray spectroscopy techniques using one triple-cluster detector of the ...

^40

Since the discovery of the breakdown of shell effects in very neutron‐rich N=20 and 28 nuclei, studies of the properties of nuclei far from stability have been of intense interest since they provide a unique opportunity to increase our understanding of nuclear interactions in extreme conditions and often challenge our theoretical models.Deep‐inelastic processes can be used to populated high spin states of neutron‐rich nuclei. In the deep‐inelastic processes, an equilibration in N/Z between the target and projectile nuclei is achieved. For most heavy neutron‐rich target nuclei, the N/Z ratio is 1.5 – 1.6, while for the possible neutron‐rich sdf‐shell projectile it is about 1.2. Thus by using deep‐inelastic processes one can populate neutron‐rich nuclei around N=20 and N=28.New results for the spectroscopy of neutron‐rich N=22 36Si and 37P are presented here.

K

Further analysis of earlier152Gd(α,4n) in-beam data revealed several previously unplaced152Dy γ-rays feeding the oblate yrast states, among them γ-transitions emitted in decay of the superdeformed band. We can also weakly detect the lowest two members of the superdeformed cascade, but our data were not quite good enough to make a firm connection to them.