6533b839fe1ef96bd12a5c0a

RESEARCH PRODUCT

Search for stable octupole deformation in $^{225}$Fr

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description

Levels in $^{225}$Fr have been studied by $\gamma$-ray and conversion-electron spectroscopy following the $\beta$-decay of $^{225}$Rn, and by the $^{226}$Ra(t,$\alpha$)$^{225}$Fr single-proton-pickup reaction. Multipolarities were obtained for $\sim$ 50 $\gamma$-transitions, and a level scheme was established in which definite spin-parity values were determined for over 20 of the 48 levels. Although low-lying rotational bands of both parities exist for $K=1/2$ and $K=3/2$, there is no experimental evidence to claim these are parity doublets. E1 strengths connecting the $K^\pi=3/2^\pm$ bands are intermediate between those for nuclides which are reflection symmetric and those claimed to be octupole deformed. The (t $\alpha$) cross-sections are in better agreement with those predicted for the reflection-symmetric case than with those from an octupole-deformed description. These observations may be confirming theoretical predictions that octupole correlations are important in $^{225}$Fr, but that there is no large stable octupole deformation.