Octupole vibrational origin of the low $K^{\pi }=0^{-}$; $I=1^{-}$ states in the $A\gtrsim 218$ Rn, Ra, and Th even-even nuclei

From an analysis of the experimental data, we assign $I^{\pi }=3^{-}$ (and $I=4^{+}$) levels in even ${}_{86}{}^{}{}_{}{}^{}\mathrm{Rn}$ nuclei. These levels, together with known levels with $I^{\pi }=1^{-}$ in ${}_{86}{}^{}{}_{}{}^{}\mathrm{Rn}$ and negative parity levels $K^{\pi }=0^{-}$; $I=1^{-},3^{-},\mathrm{and}{5}^{-}$ in ${}_{88}{}^{}{}_{}{}^{}\mathrm{Rn}$, ${}_{90}{}^{}{}_{}{}^{}\mathrm{Th}$, and ${}_{92}{}^{}{}_{}{}^{}\mathrm{U}$, demonstrate features of strong Coriolis coupling. The existence of strong Coriolis coupling effects is typical only for rotational bands based on one-phonon octupole vibrational states which include particles with large$j$ ($j_{\frac{15}{2}}$, $i_{\frac{13}{2}}$, etc.), but not for bands based on states $K^{\pi }=0^{-}$; $I=1^{-}$ with stable octupole deformation.