John F. Smith (UWS)
An experiment was performed using AGATA to characterise new structures observed in the octupole-deformed light-actinide nuclei 220Ra and 222Th. The primary goal of the experiment was to measure the linear polarizations of transitions linking new (unpublished) rotational-like structures to the yrast octupole bands in these nuclei, and in the case of 222Th, to measure the linear polarizations of inter-band dipole transitions in the new structure. AGATA was used with the 18O (95 MeV) + 208Pb fusion-evaporation reactions. It is intended that the gamma-ray interaction positions within the AGATA detectors will be used to reconstruct the scattering angles of the transitions of interest, and hence determine their linear polarizations. Establishing whether inter-band dipole transitions in the new structure in 222Th are E1 or M1 is crucial to its possible interpretation as an excited alternating-parity octupole band. Although the gamma-ray spectra will be dominated by gamma rays from fast fission, the fission background can be effectively removed by gamma-ray gating. The data are presently in the early stages of analysis.
Daniele Mengoni (PD) John F. Smith (UWS)