New collective structures in odd-odd '1²⁰I

Previous work [1] on ¹²⁰I established three collective bands in this nucleus. Expecting that a large number of collective bands exist in ¹²⁰I and they may display various interesting structural effects like coexistence between prolate and oblate shapes, we have attempted a re-investigation of this nucleus. The experiment was carried out at the HI-13 tandem accelerator of CIAE in Beijing. Fusion-evaporation reactions ¹¹⁴Cd (¹⁰B, 4n) at 48 MeV and ¹¹⁰Pd (¹⁴N, 4n) at 64 MeV were chosen to populate the excited states of ¹²⁰I. γ-γ coincidences were measured with an array consisting of 14 HPGe detectors, twelve of which were Compton-suppressed and the remaining two were detectors of LEP type. About 100 million coincidence events were recorded for each reaction. In the ¹⁰B induced reaction, ¹²⁰Te, ¹²⁰I and ¹²¹I are major products; and in contrast, ¹²⁰Te, ¹²⁰I and ¹¹⁹I are the major products in the ¹⁴N reaction. This difference provides an efficient way to distinguish γ rays of ¹²⁰I from the ones of ¹²¹I and ¹¹⁹I. In off-line analysis, several E_γ-E_γ matrices were created, including the asymmetric ones for extracting DCO ratios of γ-rays. All the previously known [1] bands have been extended. Moreover, several new rotational-like sequences have been identified. One of the newly established sequences is shown in Fig.1, where the 81, 124, 108, 634, 714, 812 keV transitions are known from previous study [1] while all the other ones are deduced from the present work. Spin and parity assignments remain un-assigned because further study is still in progress. (authors)