Nuclear Charge Radii of Th229 from Isotope and Isomer Shifts

The isotope Th229 is unique in that it possesses an isomeric state of only a few electron volts above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear p...

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Bibliographic Details
Published in:Physical review letters 2018-11, Vol.121 (21), p.213001
Main Authors: Safronova, M S, Porsev, S G, Kozlov, M G, Thielking, J, Okhapkin, M V, Głowacki, P, Meier, D M, Peik, E
Format: Article
Language:English
Subjects:
Configuration interaction
Hyperfine structure
Mossbauer spectroscopy
Nuclear properties
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Summary:The isotope Th229 is unique in that it possesses an isomeric state of only a few electron volts above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear properties of both states have to be determined precisely to derive the actual sensitivity. We carry out isotope shift calculations in Th+ and Th2+ including the specific mass shift, using a combination of configuration interaction and all-order linearized coupled-cluster methods and estimate the uncertainty of this approach. We perform experimental measurements of the hyperfine structure of Th2+ and isotopic shift between Th2+229 and Th2+232 to extract the difference in root-mean-square radii as δ⟨r2⟩232,229=0.299(15) fm2. Using the recently measured values of the isomer shift of lines of Th229m, we derive the value for the mean-square radius change between Th229 and its low-lying isomer Th229m to be δ⟨r2⟩229m,229=0.0105(13) fm2.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.121.213001