Lifetime measurement of the first $2^{+}$ state in ${}^{178}\mathrm{Pt}$

The lifetime of the $2_1^{+}$ state in ${}^{178}\mathrm{Pt}$ was measured by using fast-timing techniques with the high-purity Ge and ${\mathrm{LaBr}}_3:\mathrm{Ce}$ array using the ${}^{154}\mathrm{Gd}$(${}^{28}\mathrm{Si},4n$) reaction at a beam energy of 146 MeV. The deduced $B(E2,2_1^{+}\to 0_1^{+})$ strength is discussed in relation to the systematics of the previously reported $B(E2,2_1^{+}\to 0_1^{+})$ strengths in the light even-even ${}^{176–184}\mathrm{Pt}$ isotopes and compared with calculations of the generator coordinate method. The present results support a configuration-mixing interpretation for low-spin states in these light Pt isotopes.

Figure 1

${}^{178}\mathrm{Pt}$ energy spectra: (a) Total projection from all HPGe and ${\mathrm{LaBr}}_3:\mathrm{Ce}$ detectors. (b) ${\mathrm{LaBr}}_3:\mathrm{Ce}$ energy spectrum gated on the sum of 337.7, 413.0, and 483.0 keV transitions in the HPGe detectors. The energies marked on the peaks are in keV. The diamond labels indicate contaminations.

Figure 2

Time spectrum for decay of yrast $2^{+}$ state in ${}^{178}\mathrm{Pt}$ measured from time difference between 170.3 and 257.1 keV transitions. The dashed line shows the Gaussian distribution (determined by gating on the Compton background near the 170.3 keV peak) which approximates the prompt spectrum. The solid line is a fit to the data.

Figure 3

Systematics of the (a) $B(E2,2_1^{+}\to 0_1^{+})$, (b) $B_{4/2}$, and (c) $R_{4/2}$ values for the Pt isotopes with $98\le N\le 106$. The experimental point at $N=100$ is from the present work. Two conflicting values of $B(E2,2_1^{+}\to 0_1^{+})$ are plotted for ${}^{182}\mathrm{Pt}$ corresponding to measurements from different experimental groups. The experimental data for the other nuclei are taken from the Nuclear Data Sheets. The solid lines indicate the results calculated with the generator coordinate method (see text).

Figure 4

Particle-number and angular momentum $I=0_1^{+},2_1^{+},4_1^{+}$ projected deformation energy curves for ${}^{176–184}\mathrm{Pt}$.