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

Abstract

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.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1463481
Alternate Identifier(s):
OSTI ID: 1455100
Report Number(s):
LA-UR-17-27341
Journal ID: ISSN 2469-9926; PLRAAN; TRN: US1902303
Grant/Contract Number:  
AC52-06NA25396; 20140011DR
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review A
Additional Journal Information:
Journal Volume: 97; Journal Issue: 6; Journal ID: ISSN 2469-9926
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Crystal Structure, Nuclear Clock, Band Gap; Crystal Structure; Nuclear Clock; Band Gap; Doped Crystals

Citation Formats

Meyer, Edmund R., Timmermans, Eddy M. E., Rudin, Sven, Kress, Joel D., Collins, Lee A., and Zhao, Xinxin. Thorium-doped CsI: Implications for the thorium nuclear clock transition. United States: N. p., 2018. Web. doi:10.1103/PhysRevA.97.060503.
Meyer, Edmund R., Timmermans, Eddy M. E., Rudin, Sven, Kress, Joel D., Collins, Lee A., & Zhao, Xinxin. Thorium-doped CsI: Implications for the thorium nuclear clock transition. United States. doi:10.1103/PhysRevA.97.060503.
Meyer, Edmund R., Timmermans, Eddy M. E., Rudin, Sven, Kress, Joel D., Collins, Lee A., and Zhao, Xinxin. Wed . "Thorium-doped CsI: Implications for the thorium nuclear clock transition". United States. doi:10.1103/PhysRevA.97.060503. https://www.osti.gov/servlets/purl/1463481.
@article{osti_1463481,
title = {Thorium-doped CsI: Implications for the thorium nuclear clock transition},
author = {Meyer, Edmund R. and Timmermans, Eddy M. E. and Rudin, Sven and Kress, Joel D. and Collins, Lee A. and Zhao, Xinxin},
abstractNote = {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.},
doi = {10.1103/PhysRevA.97.060503},
journal = {Physical Review A},
number = 6,
volume = 97,
place = {United States},
year = {2018},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

FIG. 1 FIG. 1: Th:CsI optimized at GGA level of theory for 12.5% doping. The planar iodine atoms form quasi-molecular ThI4, which helps with the stability, but the planar Cs atoms form four balancing positive charges which helps to keep Th in the neutral state.

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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.