Bose-Einstein Condensation on a Permanent-Magnet Atom Chip

We have produced a Bose-Einstein condensate on a permanent-magnet atom chip based on periodically magnetized videotape. We observe the expansion and dynamics of the condensate in one of the microscopic waveguides close to the surface. The lifetime for atoms to remain trapped near this dielectric material is significantly longer than above a metal surface of the same thickness. These results illustrate the suitability of microscopic permanent-magnet structures for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com

Bose-Einstein Condensation on a Permanent-Magnet Atom Chip

We have produced a Bose-Einstein condensate on a permanent-magnet atom chip based on periodically magnetized videotape. We observe the expansion and dynamics of the condensate in one of the microscopic waveguides close to the surface. The lifetime for atoms to remain trapped near this dielectric material is significantly longer than above a metal surface of the same thickness. These results illustrate the suitability of microscopic permanent-magnet structures for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com

Spin correlations and velocity-scaling in color-octet NRQCD matrix elements

We compute spin-dependent decay matrix elements for S-wave charmonium and bottomonium in lattice nonrelativistic quantum chromodynamics (NRQCD). Particular emphasis is placed upon the color-octet matrix elements, since the corresponding production matrix elements are expected to appear in the dominant contributions to the production cross sections at large transverse momenta. We use three slightly different versions of the heavy-quark lattice Green's functions in order to minimize the contributions that scale as powers of the ultraviolet cutoff. The lattice matrix elements that we calculate obey the hierarchy that is suggested by the velocity-scaling rules of NRQCD.Comment: 25 pages, 2 figures, 2 tables, further discussion of effective lattice cutoffs and uncertainties, additional minor revisions, version to be published in Phys. Rev.

Persistent Decadal-Scale Rainfall Variability in the Tropical South Pacific Convergence Zone Through the Past Six Centuries

Modern Pacific decadal variability (PDV) has global impacts; hence records of PDV from the pre-instrumental period are needed to better inform models that are used to project future climate variability. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; similar to 9.5 degrees S, similar to 160 degrees E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between delta O-18 variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall variability from the South Pacific Convergence Zone (SPCZ). We present evidence for large (similar to 1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423 +/- 5 CE (Common Era) in the Solomon Islands. The timing of the decadal changes in rainfall inferred from the 20th-century portion of the stalagmite delta O-18 record coincides with previously identified decadal shifts in PDV-related Pacific ocean-atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate variability. The 600 yr Solomon Islands stalagmite delta O-18 record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability.Taiwan ROC NSCNTU 101-2116-M-002-009, 102-2116-M-002-016, 101R7625Geological Science

First principles study of intrinsic point defects in hexagonal barium titanate

Density functional theory (DFT) calculations have been used to study the nature of intrinsic defects in the hexagonal polymorph of barium titanate. Defect formation energies are derived for multiple charge states and due consideration is given to finite-size effects (elastic and electrostatic) and the band gap error in defective cells. Correct treatment of the chemical potential of atomic oxygen means that it is possible to circumvent the usual errors associated with the inaccuracy of DFT calculations on the oxygen dimer. Results confirm that both mono- and di-vacancies exist in their nominal charge states over the majority of the band gap. Oxygen vacancies are found to dominate the system in metal-rich conditions with face sharing oxygen vacancies being preferred over corner sharing oxygen vacancies. In oxygen-rich conditions, the dominant vacancy found depends on the Fermi level. Binding energies also show the preference for metal-oxygen di-vacancy formation. Calculated equilibrium concentrations of vacancies in the system are presented for numerous temperatures. Comparisons are drawn with the cubic polymorph as well as with previous potential-based simulations and experimental results

Doppler-free laser spectroscopy of buffer gas cooled molecular radicals

We demonstrate Doppler-free saturated absorption spectroscopy of cold molecular radicals formed by laser ablation inside a cryogenic buffer gas cell. By lowering the temperature, congested regions of the spectrum can be simplified, and by using different temperatures for different regions of the spectrum a wide range of rotational states can be studied optimally. We use the technique to study the optical spectrum of YbF radicals with a resolution of 30 MHz, measuring the magnetic hyperfine parameters of the electronic ground state. The method is suitable for high resolution spectroscopy of a great variety of molecules at controlled temperature and pressure, and is particularly well-suited to those that are difficult to produce in the gas phase.Comment: 11 pages, 4 figure

The Partition Function of Multicomponent Log-Gases

We give an expression for the partition function of a one-dimensional log-gas comprised of particles of (possibly) different integer charge at inverse temperature {\beta} = 1 (restricted to the line in the presence of a neutralizing field) in terms of the Berezin integral of an associated non- homogeneous alternating tensor. This is the analog of the de Bruijn integral identities [3] (for {\beta} = 1 and {\beta} = 4) ensembles extended to multicomponent ensembles.Comment: 14 page

First Demonstration of a Pixelated Charge Readout for Single-Phase Liquid Argon Time Projection Chambers

Liquid Argon Time Projection Chambers (LArTPCs) have been selected for the future long-baseline Deep Underground Neutrino Experiment (DUNE). To allow LArTPCs to operate in the high-multiplicity near detector environment of DUNE, a new charge readout technology is required. Traditional charge readout technologies introduce intrinsic ambiguities, combined with a slow detector response, these ambiguities have limited the performance of LArTPCs, until now. Here, we present a novel pixelated charge readout that enables the full 3D tracking capabilities of LArTPCs. We characterise the signal to noise ratio of charge readout chain, to be about 14, and demonstrate track reconstruction on 3D space points produced by the pixel readout. This pixelated charge readout makes LArTPCs a viable option for the DUNE near detector complex.Comment: 13 pages, 9 figure