The neutron-deficient even-mass Pt isotopes have long been studied for their transitionary shapes and emergence of shape coexistence; related behaviours are also observed in adjacent isotopes of Hg, Os, W and Hf. The isotopes have weakly deformed, oblate structures in their ground states and show some evidence of triaxiality. In contrast, starting from    as a transitional point, the mid-shell isotopes    exhibit prolate ground states and clear evidence of shape coexistence. The mid-shell nucleus    particularly challenges the oblate-band assignment within these complicated structures, underscoring the need for more detailed and comprehensive investigations of this midshell region.

To investigate the nuclear shape evolution, the lifetimes of the    states are valuable because they enable the extraction of the reduced transition strengths   , which in turn reveal nuclear shape deformation. However, there are significant discrepancies in    lifetimes for the A = 180-186 nuclei from the Evaluated Nuclear Structure Data File (ENSDF) database and more recent measurements using methods such as the recoil-distance method (RDM) and the Generalised Centroid Difference (GCD) method.

We will report on the results of direct-timing lifetime measurements of the    states in    using exponential-convoluted Gaussian fitting and GCD methods applied to   -fast timing data taken with LaBr3 detectors at the Australian Heavy Ion Accelerator Facility (HIAF). Incorporating these new lifetimes, we then apply an empirical multi-band-mixing model to    to clarify the underlying shape assignments. The results are presented and discussed in the context of the complex shape evolution across the platinum isotopes.

Additionally, we will present a new passive shielding for LaBr3 detectors to be incorporated into our experimental gamma-ray detector array, which was developed for future lifetime measurements.