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

Abstract

We estimate the range of the radiative lifetime and energy of the anomalous, low-energy 3/2 + (7.8± 0.5 eV) state in the 229 Th nucleus. Our phenomenological calculations are based on the available experimental data for the intensities of M 1 and E2 transitions between excited levels of the 229 Th nucleus in the K π [N nZ Λ] = 5/2 + [633] and 3/2 + [631] rotational bands. We also discuss the influence of certain branching coefficients, which affect the currently accepted measured energy of the isomeric state. From this work, we establish a favored region where the transition lifetime and energy should lie at roughly the 90% confidence level. We also suggest new nuclear physics measurements, which would significantly reduce the ambiguity in the present data.

Excitation of the Th229 nucleus via a two-photon electronic transition

“…The vertical lines in Fig. 3 denote the most recent values for the energy of the nuclear isomeric state, ranging from 7.1 eV to 7.6 eV and 7.8 eV [32,39,40]. The grey shaded area denotes the combined uncertainties of all three measurements and, thus, a recommended initial search area for the nuclear isomer.…”

“…The nuclear transition amplitudes I e ||M q ||I g are known from elaborate nuclear calculations, e.g. by Minkov and Pálffy [31], where previous estimates by Tkalya et al [32] have been refined.…”

Improving Our Knowledge on the 229mThorium Isomer: Toward a Test Bench for Time Variations of Fundamental Constants

“…[6,7] Early on, it was realized that this exotic nuclear excitation would have a widespread potential of applications if its ground-state transition could be controlled, for example, by an optical laser excitation. [6,7] Early on, it was realized that this exotic nuclear excitation would have a widespread potential of applications if its ground-state transition could be controlled, for example, by an optical laser excitation.…”

Alternative approach to populate and study the Th229 nuclear clock isomer

“…The large experimental uncertainty of 0.5 eV (corresponding to ≈ 10 nm or ≈ 120 THz) in combination with an expected narrow nuclear resonance of 10 −4 Hz, presents a practical stumbling block for the direct excitation of this nuclear transition using coherent light sources. Moreover, recent studies shed doubt on the accuracy of the current excitation energy [20]. To improve both the accuracy and the precision of the isomer's key observables, a variety of physics techniques are implemented, with one branch focusing on a direct measurement of the electromagnetic deexcitation of 229m Th embedded in a host material.…”