Speaker
Description
Investigation of high spin states of trans-lead nuclei attracted much attention in recent years. But nuclear structure of such nuclei largely remains unexplored mainly because of the difficulty in production via fusion-evaporation reactions along with large background due to much stronger and competing fission channel. Also the difficulty in extracting the targeted information and corroborating the results from the theoretical shell model calculations, that are virtually impossible for these nuclei, makes the job much more challenging.
Proton-rich Astatine (Z = 85) isotopes have not been explored in detail. The isotopes in the proximity of N = 120, with both the odd proton and odd neutron occupying high-j orbitals, have been found to exhibit magnetic rotational band structure at high angular momenta. The experiment was done using Indian National Gamma Array (INGA) of 16 Compton suppressed Clover detectors to produce 204-206At isotopes via 12C+197Au fusion reaction at 65 MeV and 75 MeV beam energy. Coincidence data with time stamps were collected using a fast DSP data acquisition system. Data sorting into coincidence matrices, cubes, angle dependent DCO and crystal orientation dependent polarization matrices were done using MARCOS sorting program, followed by projected spectral analysis using RADWARE and INGASORT softwares. A significant number of new transitions are found. DCO ratios and polarization asymmetry results were used to establish spin and electric-or-magnetic nature. New cross-over weak E2 transitions and B(M1)/B(E2) ratios confirms the ΔI = 1 MR band. A couple of transitions are identified as possible isomeric levels by fitting on the gated ΔT-spectra. A tentative level scheme of 204At is proposed.
