High spin states of 204At: isomeric states and shears band structure
Abstract
High-spin states of neutron deficient Trans-Lead nucleus 204At were populated up to 8\, MeV excitation through the 12C + 197Au fusion evaporation reaction. Decay of the associated levels through prompt and delayed γ-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric 16+ level with observed lifetime τ=52 5\, ns, was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involving 2f5/2, 1h9/2, and 1i13/2 shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~16+ - 23+ was confirmed and evaluated in more detail, including the missing cross-over E2 transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighbouring neutron deficient 202Bi, 205Rn isotones and the 203At isotope. Based on comparison of the measured B(M1)/B(E2) values for transitions along the band with the semiclassical model based estimates, the shears band of 204At was established along with the level scheme.