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 as the most promising candidate. We report on experimental and theoretical studies supporting as a new promising candidate for laser cooling. The measured and calculated electron affinities of Th are, respectively, and , 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 is determined to be rather than . The consequence of this is that there are several strong electric dipole transitions between the bound levels arising from configurations and in . The potential laser-cooling transition is with a wavelength of . The zero nuclear spin and hence lack of hyperfine structure in reduces the potential complications in laser cooling as encountered in , making a new and exciting candidate for laser cooling.
- 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)
Synopsis
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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