Appraising nuclear octupole moment contributions to the hyperfine structures in $^{211}$Fr

Abstract

Hyperfine structures of $^{211}$Fr due to the interactions of magnetic dipole ($\mu$), electric quadrupole ($Q$) and magnetic octupole ($\Omega$) moments with the electrons are investigated using the relativistic coupled-cluster (RCC) theory with an approximation of singles, doubles and important valence triples excitations in the perturbative approach. Validity of our calculations are substantiated by comparing the results with their available experimental values. Its $Q$ value has also been elevated by combining the measured hyperfine structure constant of the $7p \ ^2P_{3/2}$ state with our improved calculation. Considering the preliminary value of $\Omega$ from the nuclear shell-model, its contributions to the hyperfine structures up to the $7d \ ^2D_{5/2}$ low-lying states in $^{211}$Fr are estimated. Energy splittings of the hyperfine transitions in many states have been assessed to find out suitability to carry out their precise measurements so that $\Omega$ of $^{211}$Fr can be inferred from them unambiguously.