## Publications

17 results found

Bohman M, Grunhofer V, Smorra C,
et al., 2021, Sympathetic cooling of a trapped proton mediated by an LC circuit, *NATURE*, Vol: 596, Pages: 514-+, ISSN: 0028-0836

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- Citations: 1

Devlin JA, Borchert MJ, Erlewein S,
et al., 2021, Constraints on the Coupling between Axionlike Dark Matter and Photons Using an Antiproton Superconducting Tuned Detection Circuit in a Cryogenic Penning Trap, *PHYSICAL REVIEW LETTERS*, Vol: 126, ISSN: 0031-9007

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- Citations: 4

Ho C, Devlin JA, Rabey I,
et al., 2020, New techniques for a measurement of the electron's electric dipole moment, *New Journal of Physics*, Vol: 22, ISSN: 1367-2630

The electric dipole moment of the electron (eEDM) can be measured with high precision using heavy polar molecules. In this paper, we report on a series of new techniques that have improved the statistical sensitivity of the YbF eEDM experiment. We increase the number of molecules participating in the experiment by an order of magnitude using a carefully designed optical pumping scheme. We also increase the detection efficiency of these molecules by another order of magnitude using an optical cycling scheme. In addition, we show how to destabilise dark states and reduce backgrounds that otherwise limit the efficiency of these techniques. Together, these improvements allow us to demonstrate a statistical sensitivity of 1.8 x 10⁻²⁸ e cm after one day of measurement, which is 1.2 times the shot-noise limit. The techniques presented here are applicable to other high-precision measurements using molecules.

Smorra C, Stadnik YV, Blessing PE,
et al., 2019, Direct limits on the interaction of antiprotons with axion-like dark matter, *NATURE*, Vol: 575, Pages: 310-+, ISSN: 0028-0836

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- Citations: 20

Devlin JA, Wursten E, Harrington JA,
et al., 2019, Superconducting Solenoid System with Adjustable Shielding Factor for Precision Measurements of the Properties of the Antiproton, *PHYSICAL REVIEW APPLIED*, Vol: 12, ISSN: 2331-7019

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- Citations: 1

Caldwell L, Devlin J, Williams H,
et al., 2019, Deep Laser Cooling and Efficient Magnetic Compression of Molecules, *Physical Review Letters*, Vol: 123, ISSN: 0031-9007

We introduce a scheme for deep laser cooling of molecules based on robust dark states at zero velocity. By simulating this scheme, we show it to be a widely applicable method that can reach the recoil limit or below. We demonstrate and characterise the method experimentally, reachinga temperature of 5.4(7) μK. We solve a general problem of measuring low temperatures for large clouds by rotating the phase-space distribution and then directly imaging the complete velocity distribution. Using the same phase-space rotation method, we rapidly compress the cloud. Applying the cooling method a second time, we compress both the position and velocity distributions.

Borchert MJ, Blessing PE, Devlin JA,
et al., 2019, Measurement of Ultralow Heating Rates of a Single Antiproton in a Cryogenic Penning Trap, *PHYSICAL REVIEW LETTERS*, Vol: 122, ISSN: 0031-9007

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- Citations: 6

Devlin J, Tarbutt M, 2018, Laser cooling and magneto-optical trapping of molecules analyzed using optical Bloch equations and the Fokker-Planck-Kramers equation, *Physical Review A*, Vol: 98, ISSN: 1050-2947

We study theoretically the behavior of laser-cooled calcium monofluoride (CaF) molecules in an optical molasses and magneto-optical trap (MOT), and compare our results to recent experiments. We use multilevel optical Bloch equations to estimate the force and the diffusion constant, followed by a Fokker-Planck-Kramers equation to calculate the time evolution of the velocity distribution. The calculations are done in three dimensions, and we include all the relevant energy levels of the molecule and all the relevant frequency components of the light. Similar to simpler model systems, the velocity-dependent force curve exhibits Doppler and polarization-gradient forces of opposite signs. We show that the temperature of the MOT is governed mainly by the balance of these two forces. Our calculated MOT temperatures and photon scattering rates are in broad agreement with those measured experimentally over a wide range of parameters. In a blue-detuned molasses, the temperature is determined by the balance of polarization-gradient cooling, and heating due to momentum diffusion, with no significant contribution from Doppler heating. In the molasses, we calculate a damping rate similar to the measured one, and steady-state temperatures that have the same dependence on laser intensity and applied magnetic field as measured experimentally, but are consistently a few times smaller than measured. We attribute the higher temperatures in the experiments to fluctuations of the dipole force which are not captured by our model. We show that the photon scattering rate is strongly influenced by the presence of dark states in the system, but that the scattering rate does not go to zero even for stationary molecules because of the transient nature of the dark states.

Smorra C, Blessing PE, Borchert MJ,
et al., 2018, 350-fold improved measurement of the antiproton magnetic moment using a multi-trap method, *Hyperfine Interactions*, Vol: 239, ISSN: 0304-3843

We summarize our recent 1.5 parts per billion measurement of the antiproton magnetic moment using the multi Penning-trap system of the BASE collaboration. The result was achieved by combining the detection of individual spin-transitions of a single antiproton with a novel two-particle spectroscopy technique, which dramatically improved the data sampling rate. This measurement contributes to improve the test of the fundamental charge, parity, time reversal (CPT) invariance in the baryon sector by a factor of 350 compared to our last measurement, and by a factor of 3000 compared to the best competing measurement. We review the measurement technique and discuss the improved limits on CPT-violating physics imposed by this measurement.

Higuchi T, Harrington JA, Borchert MJ,
et al., 2018, Progress towards an improved comparison of the proton-to-antiproton charge-to-mass ratios, *HYPERFINE INTERACTIONS*, Vol: 239, ISSN: 0304-3843

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- Citations: 2

Lim J, Almond J, Trigatzis M,
et al., 2018, Laser cooled YbF molecules for measuring the electron's electric dipole moment, *Physical Review Letters*, Vol: 120, ISSN: 0031-9007

We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μK. This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically-assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and fi nd good agreement with our data.

Jarvis KN, Devlin JA, Wall TE,
et al., 2018, Blue-detuned magneto-optical trap, *Physical Review Letters*, Vol: 120, ISSN: 0031-9007

We present the properties and advantages of a new magneto-optical trap (MOT) where blue- detuned light drives ‘type-II’ transitions that have dark ground states. Using ⁸⁷Rb, we reach a radiation-pressure-limited density exceeding 10¹¹ cm⁻³ and a temperature below 30 μK. The phase-space density is higher than in normal atomic MOTs, and a million times higher than comparable red-detuned type-II MOTs, making the blue-detuned MOT particularly attractive for molecular MOTs which rely on type-II transitions. The loss of atoms from the trap is dominated by ultracold collisions between Rb atoms. For typical trapping conditions, we measure a loss rate of 1.8(4) × 10⁻¹⁰ cm³ s⁻¹.

Sauer BE, Devlin JA, Rabey IM, 2017, A big measurement of a small moment, *New Journal of Physics*, Vol: 19, ISSN: 1367-2630

A beam of ThO molecules has been used to make the most precise measurement of the electron's electric dipole moment (EDM) to date. In their recent paper, the ACME collaboration set out in detail their experimental and data analysis techniques. In a tour-de-force, they explain the many ways in which their apparatus can produce a signal which mimics the EDM and show how these systematic effects are measured and controlled.

Devlin J, Tarbutt M, 2016, Three-dimensional Doppler, polarization-gradient, and magneto-optical forces for atoms and molecules with dark states, *New Journal of Physics*, Vol: 18, ISSN: 1367-2630

We theoretically investigate the damping and trapping forces in a three-dimensional magneto-optical trap (MOT), by numerically solving the optical Bloch equations. We focus on the case where there are dark states because the atom is driven on a ”type-II" system where the angular momentum of the excited state, F', is less than or equal to that of the ground state, F. For these systems we find that the force in a three-dimensional light field has very different behaviour to its one-dimensional counterpart. This differs from the more commonly used “type-I" systems (F' = F +1) where the 1D and 3D behaviours are similar. Unlike type-I systems where, for red-detuned light, both Doppler and sub-Doppler forces damp the atomic motion towards zero velocity, in type-II systems in 3D, the Doppler force and polarization gradient force have opposite signs. As a result, the atom is driven towards a non-zero equilibrium velocity, v₀, where the two forces cancel. We find that v₀² scales linearly with the intensity of the light and is fairly insensitive to the detuning from resonance. We also discover a new magneto-optical force that alters the normal MOT force at low magnetic fields and whose influence is greatest in the type-II systems. We discuss the implications of these findings for the laser cooling and magneto-optical trapping of molecules where type-II transitions are unavoidable in realising closed optical cycling transitions.

Rabey IM, Devlin JA, Hinds EA,
et al., 2016, Low magnetic Johnson noise electric field plates for precision measurement, *Review of Scientific Instruments*, Vol: 87, ISSN: 1089-7623

We describe a parallel pair of high voltage electric field plates designed and constructed to minimise magnetic Johnson noise. They are formed by laminating glass substrates with commercially available polyimide (Kapton) tape, covered with a thin gold film. Tested in vacuum, the outgassing rate is less than 5 x 10 exp(-5) mbar.l/s. The plates have been operated at electric fields up to 8.3 kV/cm, when the leakage current is at most a few hundred pA. The design is discussed in the context of a molecular spin precession experiment to measure the permanent electric dipole moment of the electron.

Devlin J, Tarbutt MR, Kokkin DL,
et al., 2015, Measurements of the Zeeman effect in the A(2)Pi and B-2 Sigma(+) states of calcium fluoride, *Journal of Molecular Spectroscopy*, Vol: 317, Pages: 1-9, ISSN: 1096-083X

The magnetic tuning of the low rotational levels in the (v = 0) X2Σ+, (v = 0) A2Π, and (v = 0) B2Σ+ electronic states of calcium monofluoride, CaF, have been experimentally investigated using high resolution optical Zeeman spectroscopy of a cold molecular beam. The observed Zeeman shifts and splittings are successfully modeled using a traditional effective Hamiltonian approach to account for the interaction between the (v = 0) A2Π and (v = 0) B2Σ+ states. The determined magnetic g-factors for the X2Σ+, B2Σ+ and A2Π states are compared to those predicted by perturbation theory.

Sauer BE, Devlin JA, Hudson JJ,
et al., 2013, Time reversal symmetry violation in the YbF molecule, *HYPERFINE INTERACTIONS*, Vol: 214, Pages: 119-126, ISSN: 0304-3843

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- Citations: 2

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