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Title: Thorium-doped CsI: Implications for the thorium nuclear clock transition

For 229mTh isomer nucleus with an anomalously low nuclear excitation energy, E$$\star$$ (currently accepted value of 7.8 ± 0.5 eV), the bound internal conversion (BIC) decay process is caused by the excitation of a valence electron that is sensitive to the electronic structure of the atomic-sized neighborhood. For this, we analyze an experiment where an impacting Th ion is neutralized by a negatively charged ion-receiving cesium iodide (CsI) surface, to obtain the minimal nuclear excitation energy E$$\star\atop{min}$$ necessary for BIC promotion of a Th-impurity valence electron in a CsI matrix. We analyze two cases: CsI with Th deposited into the bulk and with Th deposited on the CsI surface. In the bulk we consider band gap effects while on the surface we consider the work function. The energy to pull the electron to the surface is 1.5 – 2.2 eV depending on the surface plane, while to promote to the conduction band in the bulk it is 1.5 eV. Therefore we conclude that the Th-surface interaction can significantly reduce the lower E$$\star$$ bound of 6.3 eV, as estimated from the direct observation of the Th-clock transition [von der Wense et al., Nature (London) 533, 47 (2016)]. We suggest coating the multichannel plate with differing materials leading to different Th-impurity gaps and work functions can further narrow the E$$\star$$ uncertainty interval.
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 2469-9926; PLRAAN
Grant/Contract Number:
AC52-06NA25396; 20140011DR
Accepted Manuscript
Journal Name:
Physical Review A
Additional Journal Information:
Journal Volume: 97; Journal Issue: 6; Journal ID: ISSN 2469-9926
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Crystal Structure; Nuclear Clock; Band Gap; Doped Crystals; atomic, optical & lattice clocks; isomer decays
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1455100