Fig. 4.

Systematic behaviour of radon isotopes. a Systematics of the energies for different spins of low-lying positive-parity (black) and negative-parity states (red) in radon isotopes; b cartoon illustrating how the octupole phonon vector aligns with the rotation (R) vector (which is orthogonal to the rotating body’s symmetry axis) so that I = R + 3$ħ$ and $\mathrm{\Delta }{i}_x=3ħ$; c difference in aligned spin for negative- and positive-parity states in ^218-224Rn (re-analysed for ^218-222Rn that have been presented earlier²³). The dashed line at $\mathrm{\Delta }{i}_x=0$ is the expected value for static-octupole deformation