Experimental and theoretical study of the nuclear structure ofFr223

Abstract

The experimental level structure of Fr has been studied using the 1.470 alpha decay of 21.8 yr Ac and subsequent gamma rays to extend the level scheme recently observed following the P decay of Rn. The level structure of Fr was also studied theoretically by using the quasiparticle model of Soloviev with octupole degrees of freedom. Both experimentally and theoretically there is strong evidence that Fr is reBection asymmetric. The theoretical study of microscopic structure of several of the positive-parity bands also indicates the presence of important Nilsson configurations arising from the shell below. The comparison of the level structures of Fr, Fr, and Fr tends to elaborate the mechanism by which the octupole-modified Nilsson orbitals collapse into the more degenerate shell model states as the mass number decreases.PACS number(s): 21.60. Ev, 23.60.+e, 27.90.+b

EnhancedT-odd,P-odd electromagnetic moments in reflection asymmetric nuclei

“…The mixing coefficient is therefore enhanced only in a few cases when single-particle deformed levels are accidentally close and the approximation of Eqs. (53,54) becomes a crude one [18]. In the reflection-asymmetric case always [14,40,38]…”

“…The case of Fr is especially interesting in light of the recent experiments involving trapping of Fr atoms [51]. The latest experimental and theoretical studies of 221 Fr [52] and 223 Fr [53,54] provide strong evidence of intrinsic reflection asymmetry in the g.s. The g.s of 221 Fr is K π = 1 2 − , I π = 5 2 − .…”

Nuclei with enhanced Schiff moments in practical elements for atomic and molecular EDM measurements

“…Concerning excited states, it's instructive to note that 221 Fr is a rather complex "transition" nucleus; e.g., its possible static octupole deformed excited parity-doublet band actually has spins out of order in energy. This is understood as a case in neutron number N between 219 Fr, which has no special deformation, and 223 Fr, which has "fairly strong" evidence [42] from its structure and feeding from alpha-and beta-decay for a static octupole deformation parity doublet, albeit with a relatively large parity-doublet splitting of 161 keV. The experimental parity doublet of 223 Fr has been modelled including admixtures with static octupole and collective octupole vibrations [42]; however, E1 transitions between the 223 Fr bands were later found to be relatively weak, consistent with 223 Fr having collective octupole vibrations [43,44,45].…”

Inverse odd-even staggering in nuclear charge radii and possible octupole collectivity in At217,218,219 revealed by in-source laser spectroscopy

“…2). Indeed, the I π = 3/2 − ground state of 223 Fr is presumed to have a deformed 3/2 − [521] f 7/2 Nilsson configuration, which is strongly mixed with the 1/2 − [521]h 9/2 band [39].…”