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Register a new userPrecision measurement of the nuclear polarization in laser-cooled, optically pumped $^{37}mathrm{K}$
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We report a measurement of the nuclear polarization of laser-cooled, optically-pumped $^{37}mathrm{K}$ atoms which will allow us to precisely measure angular correlation parameters in the beta-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 (MOT) confines and cools neutral $^{37}mathrm{K}$ 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 $P = 0.9913pm0.0008$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the beta-asymmetry has $0.2%$ 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.
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Using TRIUMFs neutral atom trap, TRINAT, for nuclear $beta$ decay, we have measured the $beta$ asymmetry with respect to the initial nuclear spin in $^{37}mathrm{K}$ to be $A_beta=-0.5707(13)_mathrm{syst}(13)_mathrm{stat}(5)_mathrm{pol}$, a 0.3% measurement. This is the best relative accuracy of any $beta$-asymmetry measurement in a nucleus or the neutron, and is in agreement with the standard model prediction $-0.5706(7)$. We compare constraints on physics beyond the standard model with other $beta$-decay measurements, and improve the value of $V_mathrm{ud}$ measured in this mirror nucleus by a factor of 4.
We report precision measurements of the nuclear magnetic moment of textsuperscript{43}Catextsuperscript{+}, made by microwave spectroscopy of the 4s $^2$S$_{1/2}$ $left|F=4, M=0rightrangle rightarrow left|F=3, M=1rightrangle$ ground level hyperfine clock transition at a magnetic field of $approx$ 146 G, using a single laser-cooled ion in a Paul trap. We measure a clock transition frequency of $f = 3199941076.920 pm 0.046$ Hz, from which we determine $mu_I / mu_{rm{N}} = -1.315350(9)(1)$, where the uncertainty (9) arises from uncertainty in the hyperfine $A$ constant, and the (1) arises from the uncertainty in our measurement. This measurement is not corrected for diamagnetic shielding due to the bound electrons. We make a second measurement which is less precise but agrees with the first. We use our $mu_I$ value, in combination with previous NMR results, to extract the change in shielding constant of calcium ions due to solvation in D$_2$O: $Delta sigma = -0.00022(1)$.
The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at PSI using a modular high pressure ionization chamber. The rate corresponding to statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1. This result confirms the PCAC prediction for the pseudoscalar form factors of the 3He-3H system and the nucleon.
The last few years have seen rapid progress in the application of laser cooling to molecules. In this review, we examine what kinds of molecules can be laser cooled, how to design a suitable cooling scheme, and how the cooling can be understood and modelled. We review recent work on laser slowing, magneto-optical trapping, sub-Doppler cooling, and the confinement of molecules in conservative traps, with a focus on the fundamental principles of each technique. Finally, we explore some of the exciting applications of laser-cooled molecules that should be accessible in the near term.
Hyperfine structure (HFS) of atomic energy levels arises due to interactions of atomic electrons with a hierarchy of nuclear multipole moments, including magnetic dipole, electric quadrupole and higher rank moments. Recently, a determination of the magnetic octupole moment of the $^{173}mathrm{Yb}$ nucleus was reported from HFS measurements in neutral ${}^{173}mathrm{Yb}$ [PRA 87, 012512 (2013)], and is four orders of magnitude larger than the nuclear theory prediction. Considering this substantial discrepancy between the spectroscopically extracted value and nuclear theory, here we propose to use an alternative system to resolve this tension, a singly charged ion of the same $^{173}mathrm{Yb}$ isotope. Utilizing the substantial suite of tools developed around $mathrm{Yb}^+$ for quantum information applications, we propose to extract nuclear octupole and hexadecapole moments from measuring hyperfine splittings in the extremely long lived first excited state ($4f^{13}(^2!F^{o})6s^2$, $J=7/2$) of $^{173}mathrm{Yb}^+$. We present results of atomic structure calculations in support of the proposed measurements.
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