The ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ β decay was reinvestigated using high-resolution single γ spectrometry as well as γ-γ coincidence techniques. For single γ-spectra measurements, radiochemically pure ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ sources were obtained by chromatographic separation from a 75 MBq activity ${}_{}{}^{227}{}_{}{}^{}\mathrm{Ac}$ parent source and continuously purified of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ and daughters. The analysis of the γ spectra of 30 sources showed the existence of 131 γ lines, of which 87 are reported for the first time in the ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ β decay although many of them are observed following the ${}_{}{}^{227}{}_{}{}^{}\mathrm{Th}$ α decay. The ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ half-life was remeasured and found to be ${\mathit{T}}_{1/2}$=22.00±0.07 min. γ-γ-t coincidence measurements were also carried out with ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ purified sources. The ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ level scheme was built on the basis of our γ data, as well as ${}_{}{}^{227}{}_{}{}^{}\mathrm{Th}$ α-decay data. Among the 32 excited ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ levels, of which 22 were also known from ${}_{}{}^{227}{}_{}{}^{}\mathrm{Th}$ α decay, 13 are newly reported from ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ β decay. Low energy levels (E<400 keV) may be classified as parity doublet bands according to the predictions of the reflection asymmetric rotor model. Above a 700 keV gap, a coexistence of symmetric and asymmetric shapes including both static and dynamic octupole correlations is suggested.

• Received 27 February 1992

DOI:https://doi.org/10.1103/PhysRevC.47.94