Structural Diversity in Iodine Isotopes: Comparison with Model Calculations

The properties of high spin states in (Z = 53) ^{113}I, ^ {117}I, ^{121} I and ^{125,127}I nuclei have been investigated using the techniques of gamma-spectroscopy. A surprisingly broad diversity of nuclear structure effects has been observed across the 60 < N < 74 isotopic chain. The experimental results have been interpreted within the framework of several nuclear models. In ^{113}I, five well-deformed intruder bands have been observed. The properties of these bands indicate a mode of "soft" band termination, which involves the gradual alignment of valence nucleons along the axis of rotation. Associated with this process is a shape change from the prolate (gamma = 0 ^circ) shape to a noncollective oblate (gamma = +60^circ ) band terminating configuration. In the neutron mid-shell nucleus ^{117}I, attention has been focussed on coexisting prolate ( gamma = 0^circ) and collective oblate (gamma = -60^circ) bands originating on the same (pi h_{11/2} ) orbital. In addition, a non-collective oblate (gamma = +60^circ ) band terminating state was also observed. In ^{121}I, large decay hindrances between oblate and prolate shapes have been inferred from lifetime measurements using the recoil-distance (plunger) technique. In the dual study of ^{125,127 }I, a decrease in the rotational collectivity and a preference for vibrational modes is noted as the isotopic chain extends towards the N = 82 magic neutron shell closure.