Nuclear structure ofTh229

Abstract

Lifetimes of excited states in 229 Th, populated in the β decay of 229 Ac, have been measured using the advanced time-delayed βγ γ (t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new γ lines have been introduced into the β-decay scheme of 229 Ac based on results of γ γ coincidence measurements. Reduced transition probabilities have been determined for more than 70 γ transitions in 229 Th. Average |D 0 | values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K π = 1/2 ± , 3/2 ± , and 5/2 ± parity partner bands, respectively. Excited states in 229 Th and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2 + isomeric state is predicted to be about 10 h. Potential energy surfaces on the (β 2 , β 3 ) plane for the lowest single quasiparticle configurations in 229 Th have been calculated using the Strutinsky method.

Radiative lifetime and energy of the low-energy isomeric level inTh229

“…III) than b 29 , leading to a smaller shift of 0.2 eV and the currently accepted value of E is = 7.8 ± 0.5 eV. Interestingly, the same branching ratios can be obtained from the experimental data [46][47][48][49] for parameters of interband (see in Figure 1 Table III, where the probabilities of the inband transitions were calculated using the internal quadrupole moment Q 20 and the difference of the rotational and internal gyromagnetic ratio g R and g K , respectively (for the rotational band 5/2…”

“…Such an experiment would ideally resolve the tension between the current results of Ref. [46][47][48][49]. This would allow accurate values of b 29 and b 42 to be calculated.…”

“…III, the measurements of Refs. [46][47][48][49] can be used to bound the isomeric level half life. In this section we will use the radiation lifetime instead of half-life, which is traditionally used in atomic spectroscopy.…”

Nuclear structure of lowestTh229states and time-dependent fundamental constants

“…We should like to point out that the Nilsson orbit 5/2 + [633] that is usually used to classify the K π = 5/2 + ground state band [9,41,42] In Ref. [41,43] experimental data have been compared with structure calculations for 229 Th that use the quasiparticle-phonon model [44] employing a phenomenological Nilsson mean field and multipolemultipole residual interactions.…”

“…[41,43] experimental data have been compared with structure calculations for 229 Th that use the quasiparticle-phonon model [44] employing a phenomenological Nilsson mean field and multipolemultipole residual interactions. A very good description of the 229 Th level structure has been achieved by an appropriate fit of the interaction parameters.…”