Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37K

B. Fenker*, J. A. Behr, D. Melconian, R. M.A. Anderson, M. Anholm, D. Ashery, R. S. Behling, I. Cohen, I. Craiciu, J. M. Donohue, C. Farfan, D. Friesen, A. Gorelov, J. McNeil, M. Mehlman, H. Norton, K. Olchanski, S. Smale, O. Thériault, A. N. VantyghemC. L. Warner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in the -decay of the same atoms. These results will be used to test the V - A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of P = 0.9913 ±0.0009, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to < 0.1%, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.

Original languageEnglish
Article number073028
JournalNew Journal of Physics
Issue number7
StatePublished - Jul 2016


  • Beta-decay
  • atom trapping
  • fundamental symmetries
  • optical pumping
  • parity violation


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