High spin spectroscopy in ${}^{219}\mathrm{Ra}$: Search for the lower mass boundary of the region of statically octupole-deformed nuclei

We report the results of a study of rotational bands in ${}^{219}\mathrm{Ra}$ via the ${}^{208}\mathrm{Pb}({}^{14}\mathrm{C},3n)$ reaction to look for evidence that this nucleus is statically octupole deformed. We add 19 $\gamma$ rays not previously observed to the level scheme and extend the two most strongly populated alternating parity bands to $J=51/2$ and 45/2. The magnitude of the energy splitting between the spin-parity doublets in the two bands appears to exclude the possibility that ${}^{219}\mathrm{Ra}$ has a static octupole deformation.

Figure 1

Level scheme of ${}^{219}\mathrm{Ra}$ determined in the present work. The states and transitions drawn in red were not observed in previous studies.

Figure 2

Evidence for new $E2$ transitions in Band 1. The spectrum is gated on the 477 keV $\gamma$ ray, which is a doublet. The peaks labeled in red were not observed in previous studies.

Figure 3

Evidence for new $E1$ transitions in Band 1. The upper panel is gated on the 504 keV transition. The lower panel is the sum of spectra gated on the 276, 477, 228, 249, 504, and 270 keV transitions. The peaks labeled in red were not observed in previous studies.

Figure 4

Evidence for new $E2$ transitions in Band 2. The upper panel shows the sum of spectra gated on 458, 129, 333, 249, 387, 307, 412, 312, 100, 300, 320, and 324 keV $\gamma$ rays. The 477 keV peak seen in this panel is a contaminant from Band 1. The lower panel displays the spectrum gated on the 435 keV $\gamma$ ray. The peaks labeled in red were not observed in previous studies.

Figure 5

Evidence for new $E1$ transitions in Band 2 from the spectrum gated on the 306 keV $\gamma$ ray. The peaks labeled in red were not observed in previous studies.

Figure 6

DCO ratios for transitions in Band I, as described in the text.

Figure 7

Energy splitting between candidates for simplex partner bands in ${}^{219,221}\mathrm{Ra}$ and ${}^{221,223}\mathrm{Th}$. Details are given in the text. The data are taken from Refs. [6, 7, 11, 12, 13] and the present work.