Active stabilization of kilogauss magnetic fields to the ppm level for magnetoassociation on ultranarrow Feshbach resonances.

Feshbach association of ultracold molecules using narrow resonances requires exquisite control of the applied magnetic field. Here, we present a magnetic field control system to deliver magnetic fields of over 1000 G with ppm-level precision integrated into an ultracold-atom experimental setup. We combine a battery-powered, current-stabilized power supply with active feedback stabilization of the magnetic field using fluxgate magnetic field sensors. As a real-world test, we perform microwave spectroscopy of ultracold Rb atoms and demonstrate an upper limit on our magnetic field stability of 2.4(3) mG at 1050 G [2.3(3) ppm relative] as determined from the spectral feature.

Author Correction: Weakly bound molecules as sensors of new gravitylike forces.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Weakly bound molecules as sensors of new gravitylike forces.

Several extensions to the Standard Model of particle physics, including light dark matter candidates and unification theories predict deviations from Newton's law of gravitation. For macroscopic distances, the inverse-square law of gravitation is well confirmed by astrophysical observations and laboratory experiments. At micrometer and shorter length scales, however, even the state-of-the-art constraints on deviations from gravitational interaction, whether provided by neutron scattering or precise measurements of forces between macroscopic bodies, are currently many orders of magnitude larger than gravity itself. Here we show that precision spectroscopy of weakly bound molecules can be used to constrain non-Newtonian interactions between atoms. A proof-of-principle demonstration using recent data from photoassociation spectroscopy of weakly bound Yb2 molecules yields constraints on these new interactions that are already close to state-of-the-art neutron scattering experiments. At the same time, with the development of the recently proposed optical molecular clocks, the neutron scattering constraints could be surpassed by at least two orders of magnitude.

Energy expenditure for massage therapists during performing selected classical massage techniques.

OBJECTIVES: The aim of the study is to evaluate the intensity of the effort and energy expenditure in the course of performing selected classical massage techniques and to assess the workload of a massage therapist during a work shift. MATERIAL AND METHODS: Thirteen massage therapists (age: 21.9±1.9 years old, body mass index: 24.5±2.8 kg×m-2, maximal oxygen consumption × body mass-1 (VO2max×BM-1): 42.3±7 ml×kg-1×min-1) were involved in the study. The stress test consisted in performing selected classical massage techniques in the following order: stroking, kneading, shaking, beating, rubbing and direct vibration, during which the cardio-respiratory responses and the subjective rating of perceived exertion (RPE) were assessed. Intensity of exercise during each massage technique was expressed as % VO2max, % maximal heart rate (HRmax) and % heart rate reserve (HRR). During each massage technique, net energy expenditure (EE) and energy cost of work using metabolic equivalent of task (MET) were determined. RESULTS: The intensity of exercise was 47.2±6.2% as expressed in terms of % VO2max, and 74.7±3.2% as expressed in terms of % HRmax, while it was 47.8±1.7% on average when expressed in terms of % HRR during the whole procedure. While performing the classical massage, the average EE and MET were 5.6±0.9 kcal×min-1 and 5.6±0.2, respectively. The average RPE calculated for the entire procedure was 12.1±1.4. During the performance of a classical massage technique for a single treatment during the study, the average total EE was 176.5±29.6 kcal, resulting in an energy expenditure of 336.2±56.4 kcal×h-1. In the case of the classical massage technique, rubbing was the highest intensity exercise for the masseur who performed the massage (%VO2max = 57.4±13.1%, HRmax = 79.6±7.7%, HRR = 58.5±13.1%, MET = 6.7±1.1, EE = 7.1±1.4 kcal×min-1, RPE = 13.4±1.3). CONCLUSIONS: In the objective assessment, physical exercise while performing a single classical massage is characterized by hard work. The technique of classical massage during which the masseur performs the highest exercise intensity is rubbing. According to the classification of work intensity based on energy expenditure, the masseur's work is considered heavy during the whole work shift. Int J Occup Med Environ Health 2018;31(5):677-684.

Optical Lattice Clocks with Weakly Bound Molecules.

Optical molecular clocks promise unparalleled sensitivity to the temporal variation of the electron-to-proton mass ratio and insight into possible new physics beyond the standard model. We propose to realize a molecular clock with bosonic ^{174}Yb_{2} molecules, where the forbidden ^{1}S_{0}→^{3}P_{0} clock transition would be induced magnetically. The use of a bosonic species avoids possible complications due to the hyperfine structure present in fermionic species. While direct clock line photoassociation would be challenging, weakly bound ground state molecules could be produced by stimulated Raman adiabatic passage and used instead. The recent scattering measurements [L. Franchi, et al. New J. Phys. 19, 103037 (2017)NJOPFM1367-263010.1088/1367-2630/aa8fb4] enable us to determine the positions of target ^{1}S_{0}+^{3}P_{0} vibrational levels and calculate the Franck-Condon factors for clock transitions between ground and excited molecular states. The resulting magnetically induced Rabi frequencies are similar to those for atoms hinting that an experimental realization is feasible. A successful observation could pave the way towards Hz-level molecular spectroscopy.

Self-referenced, accurate and sensitive optical frequency comb spectroscopy with a virtually imaged phased array spectrometer.

We present a cavity-enhanced direct optical frequency comb spectroscopy system with a virtually imaged phased array (VIPA) spectrometer and either a dither or a Pound-Drever-Hall (PDH) locking scheme used for stable transmission of the comb through the cavity. A self-referenced scheme for frequency axis calibration is shown along with an analysis of its accuracy. A careful comparison between both locking schemes is performed based on near-IR measurements of the carbon monoxide ν=3←0 band P branch transitions in a gas sample with known composition. The noise-equivalent absorptions (NEA) for the PDH and dither schemes are 9.9×10(-10) cm(-1) and 5.3×10(-9) cm(-1), respectively.

Interactions and collisions of discrete breathers in two-species Bose-Einstein condensates in optical lattices.

The dynamics of static and traveling breathers in two-species Bose-Einstein condensates in a one-dimensional optical lattice is modelled within the tight-binding approximation. Two coupled discrete nonlinear Schrödinger equations describe the interaction of the condensates in two cases of relevance: a mixture of two ytterbium isotopes and a mixture of (87)Rb and (41)K. Depending on their initial separation, interaction between static breathers of different species can lead to the formation of symbiotic structures and transform one of the breathers from a static into a traveling one. Collisions between traveling and static discrete breathers composed of different species are separated into four distinct regimes ranging from totally elastic when the interspecies interaction is highly attractive to mutual destruction when the interaction is sufficiently large and repulsive. We provide an explanation of the collision features in terms of the interspecies coupling and the negative effective mass of the discrete breathers.

Controlled production of subradiant states of a diatomic molecule in an optical lattice.

We report the successful production of subradiant states of a two-atom system in a three-dimensional optical lattice starting from doubly occupied sites in a Mott insulator phase of a quantum gas of atomic ytterbium. We can selectively produce either a subradiant 1(g) state or a superradiant 0(u) state by choosing the excitation laser frequency. The inherent weak excitation rate for the subradiant 1(g) state is overcome by the increased atomic density due to the tight confinement in a three-dimensional optical lattice. Our experimental measurements of binding energies, linewidth, and Zeeman shift confirm the observation of subradiant levels of the 1(g) state of the Yb(2) molecule.