Measurement of the Th229 Isomer Energy with a Magnetic Microcalorimeter

• DOI: 10.1103/physrevlett.125.142503
• Publication Date: 2020-09-28T20:48:09Z
• Authors: Tomas Sikorsky; Jeschua Geist; Daniel Hengstler; Sebastian Kempf; Loredana Gastaldo; Christian Enss; Christoph Mokry; Jörg Runke; Christoph E. Düll...; Peter Wobrauschek; Kjeld Beeks; Veronika Rosecker; Johannes H. Sterba; Georgy Kazakov; Thorsten Schumm; Andreas Fleischmann
• Keywords: ddc:620; Physics - Instrumentation and Detectors; Nuclear Theory; FOS: Physical sciences; Instrumentation and Detectors (physics.ins-det); 01 natural sciences; 620; Nuclear Theory (nucl-th); 0103 physical sciences; Nuclear Experiment (nucl-ex); info:eu-repo/classification/ddc/530; Nuclear Experiment; Engineering & allied operations; info:eu-repo/classification/ddc/620

We present a measurement of the low-energy (0–60 keV) γ-ray spectrum produced in α decay U233 using dedicated cryogenic magnetic microcalorimeter. The energy resolution ∼10 eV, together with exceptional gain linearity, allows us to determine low-lying isomeric state Th229 four complementary evaluation schemes. most precise scheme determines isomer be 8.10(17) corresponding 153.1(32) nm, superseding precision previous values based on γ spectroscopy, and agreeing recent internal conversion electrons. also measure branching ratios relevant excited states b29=9.3(6)% b42<0.7%.Received 28 May 2020Revised 8 July 2020Accepted 20 August 2020DOI:https://doi.org/10.1103/PhysRevLett.125.142503© 2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayAtomic & molecular structureNuclear structure decaysAtomic, Molecular OpticalInterdisciplinary PhysicsNuclear Physics