Low-lying electromagnetic transition strengths in ${}^{180}\mathrm{Pt}$

Lifetime measurements have been performed using the ${}^{98}\mathrm{Mo}$(${}^{86}\mathrm{Kr},4n$)${}^{180}\mathrm{Pt}$ reaction at a beam energy of 380 MeV, and the recoil distance Doppler-shift method. In a second experiment the ${}^{168}\mathrm{Yb}$(${}^{16}\mathrm{O},4n$)${}^{180}\mathrm{Pt}$ reaction at a beam energy of 88 MeV using the Ge-gated $\gamma -\gamma$ fast timing technique was used to determine lifetimes. Lifetimes of the four lowest yrast states of ${}^{180}\mathrm{Pt}$ have been determined. The experimental data are compared to calculations within the framework of the interacting boson model and the general collective model. Both models predict a deformed ground state and are consistent with all the remaining experimental results.

Figure 1

$\gamma$-ray energy spectrum measured with the detectors in the ring at ${133}^{\circ }$ (10 detectors). This is the sum over all distances with a gate on both components of the $2_1^{+}\to 0_1^{+}$ transition (including the clover detectors around ${90}^{\circ }$). Despite one random coincidence with the strong Coulomb excitation of ${}^{197}\mathrm{Au}$ the spectrum is very clean. The initial states with their depopulating shifted and unshifted components are marked with “sh” and “us”, respectively.

Figure 2

$\tau$-curve (a) of the $6_1^{+}$ state in ${}^{180}\mathrm{Pt}$ using the detector ring at ${133}^{\circ }$ with a gate on the feeding $8_1^{+}$ state in all backward angle detectors. In addition, the intensities of the shifted (b) and unshifted (c) components are shown.

Figure 3

PRD curve of the electronics using a ${}^{152}\mathrm{Eu}$ source.

Figure 4

Time-difference spectra of the $4_1^{+}$ state. The difference of the centroids between the delayed and antidelayed spectra corresponds, after correction for the PRD, to twice the lifetime of the state.

Figure 5

Fit of the convolution of a prompt peak with the lifetime of the $2_1^{+}$ state. Also the corresponding prompt peak (dotted) is plotted to show the low statistics in the tail.

Figure 6

Potential energy surface extracted from the GCM calculation.

Figure 7

Placement of ${}^{180}\mathrm{Pt}$ in the Casten triangle.

Figure 8

Comparison of the IBM calculation (a), the experimental values (b), and the GCM calculation (c). Shown are the level energies for the ground state, $\beta$ and $\gamma$ bands, and the third $0^{+}$ state. The $B\left(E2\right)$ values are summarized in Table 1.

Figure 9

Transition quadrupole moments for the $N=102$ isotone around Pt. $\pi$ and $\nu$ are the valence proton and neutron number, respectively. Experimental values taken from [7, 32, 33]. The indicated deformations are calculated from the lowest quadrupole moment neglecting variations described by the collective models; just for the case of ${}^{182}\mathrm{Hg}$ the near constant deformation for the excited states is given as well.