The radioactive radium-225 (225Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, 225Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of 225Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d(225Ra)|<5.0×10−22  e cm (95% confidence).

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Published in Physical Review Letters, v. 114, no. 23, article 233002, p. 1-5.

©2015 American Physical Society

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This work is supported by the Department of Energy (DOE), Office of Science, Office of Nuclear Physics, under Contracts No. DEAC02-06CH11357 and No. DE-FG02-99ER41101. Ra225 used in this research was supplied by DOE, Office of Science, Isotope Program in the Office of Nuclear Physics. M. B., N. D. L., and J. T. S. acknowledge support from Argonne Director’s postdoctoral fellowships.

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