LABORATORI NAZIONALI DI LEGNARO
The super-deformed bands have been in focus of experimental nuclear physics studies for past decades. They have been reported in several regions of the nuclear chart and since then have become a new challange for the nuclear structure theory. Very recently this phenomenon has been discovered in the A_40 mass region. Unlike in the heavier nuclei, in calcium region the strongly deformed bands are linked to the normal deformed bands with the discreet gamma transitions, suggesting a possible mixing between those structures. Up to now the SD structures have been populated in fusion-evaporation reactions and B(E2) values were extracted from lifetime measurements. Very recently a Coulomb excitation technique was used for the first time in a dedicated project to populate such a highly-deformed band in atomic nucleus and to study its decay. The experiment was performed at the Laboratori Nazionali di Legnaro in Italy. Gamma rays from Coulomb excited 42Ca nuclei were measured in coincidence with calcium projectiles back-scattered on 208Pb and 197Au targets and detected by three position-sensitive MCP detectors forming the DANTE array. For this study, the AGATA Demonstrator spectrometer consisted of three triple clusters was used for the first time in a nuclear physics experiment. The level of statistics was sufficient to extract a rich set of matrix elements describing the electromagnetic properties of low-lying yrast and non-yrast states in 42Ca. The deformation parameters for 0+ and 2+ states in both bands were determined, as well as the triaxiality parameters for the ground state and first excited 0+ states. The results, suggesting that two structures differing both in overall deformation and triaxiality coexist in 42Ca, are compared to large-scale Shell Model and AMD calculations. In this talk I will show both the benefits and the challenges of applying the Coulomb excitation method to study SD structures in atomic nuclei. I will focus on the status and the current results of the ongoing COULEX project in A 40 mass region.

DATA: 09-07-2015