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Candidate for Laser Cooling of a Negative Ion: High-Resolution Photoelectron Imaging of Th

Rulin Tang, Ran Si, Zejie Fei, Xiaoxi Fu, Yuzhu Lu, Tomas Brage, Hongtao Liu, Chongyang Chen, and Chuangang Ning
Phys. Rev. Lett. 123, 203002 – Published 12 November 2019
Physics logo See Synopsis: A New Negative Ion Takes the Cooling Spotlight
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Abstract

Laser cooling is a well-established technique for the creation of ensembles of ultracold neutral atoms or positive ions. This ability has opened many exciting new research fields over the past 40 years. However, no negatively charged ions have been directly laser cooled because a cycling transition is very rare in atomic anions. Efforts of more than a decade currently have La as the most promising candidate. We report on experimental and theoretical studies supporting Th as a new promising candidate for laser cooling. The measured and calculated electron affinities of Th are, respectively, 4901.35(48)cm1 and 4832cm1, or 0.607 690(60) and 0.599 eV, almost a factor of 2 larger than the previous theoretical value of 0.368 eV. The ground state of Th is determined to be 6d37s2F43/2e rather than 6d27s27pG45/2o. The consequence of this is that there are several strong electric dipole transitions between the bound levels arising from configurations 6d37s2 and 6d27s27p in Th. The potential laser-cooling transition is S1/2o2F43/2e with a wavelength of 2.6μm. The zero nuclear spin and hence lack of hyperfine structure in Th reduces the potential complications in laser cooling as encountered in La, making Th a new and exciting candidate for laser cooling.

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  • Received 9 June 2019
  • Revised 14 August 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.203002

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Synopsis

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A New Negative Ion Takes the Cooling Spotlight

Published 12 November 2019

Measurements of the electron binding energy in the negative thorium ion suggest that it may be a good candidate for laser cooling.

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Authors & Affiliations

Rulin Tang1,§, Ran Si2,3,§, Zejie Fei4, Xiaoxi Fu1, Yuzhu Lu1, Tomas Brage2,3, Hongtao Liu4,*, Chongyang Chen3,†, and Chuangang Ning1,5,‡

  • 1Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
  • 2Lund University, Department of Physics, P.O. Box 118, 221 00 Lund, Sweden
  • 3Shanghai EBIT Lab, Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China
  • 4Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
  • 5Collaborative Innovation Center of Quantum Matter, Beijing 100084, China

  • *liuhongtao@sinap.ac.cn
  • chychen@fudan.edu.cn
  • ningcg@tsinghua.edu.cn
  • §These authors contributed equally to this work.

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Issue

Vol. 123, Iss. 20 — 15 November 2019

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