We study polarization spectroscopy of Rb vapour. A weak probe beam analyses the birefringence induced in a room temperature vapour by a strong counterpropagating circularly polarized pump beam. In contrast to most other work on polarization spectroscopy, we use a polarization beam splitting cube and two detectors (rather than a polarizer and one detector) to analyse the probe beam. The signal is in the form of a derivative of a Lorentzian. For theoretical analysis we study the closed atomic transition 5 2 S 1/2 (F = 3) → 5 2 P 3/2 (F = 4) in the D2 line of 85 Rb. We study the time needed to redistribute population among the m F states, derive an expression for the expected lineshape and present experimental data in excellent agreement with theory. The polarization spectrum provides an ideal error signal for frequency stabilization of a laser. We describe the geometry and parameters for optimizing the error signal.

. (2013) A surface-patterned chip as a strong source of ultracold atoms for quantum technologies. Nature Nanotechnology, 8 (5). pp. 321-324. Copyright © 2013 MacMillanA copy can be downloaded for personal non-commercial research or study, without prior permission or chargeThe content must not be changed in any way or reproduced in any format or medium without the formal permission of the copyright holder(s) Laser cooled atoms are central to modern precision measurements 1-6 . They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics 7,8 , quantum information processing 9-11 and matter wave interferometry 12 . Although significant progress has been made in miniaturising atomic metrological devices 13,14 , these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefit from the advantages of atoms in the microKelvin regime 15,16 . However, simplifying atomic cooling and loading using microfabrication technology has proved difficult 17,18 . In this letter we address this problem, realising an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, at sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with the simplicity of fabrication and the ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices.

Cold atom setups are now commonly employed in simulations of condensed matter phenomena. We present an approach to induce strong magnetic interactions between atoms on a self-organized lattice using diffraction of light. Diffractive propagation of structured light fields leads to an exchange between phase and amplitude modulated planes which can be used to couple atomic degrees of freedom via optical pumping nonlinearities. In the experiment a cold cloud of Rb atoms placed near a retro-reflecting mirror is driven by a detuned pump laser. We demonstrate spontaneous magnetic ordering in the Zeeman sublevels of the atomic ground state: anti-ferromagnetic structures on a square lattice and ferrimagnetic structures on a hexagonal lattice in zero and a weak longitudinal magnetic field, respectively. The ordered state is destroyed by a transverse magnetic field via coherent dynamics. A connection to the transverse (quantum) Ising model is drawn.

In this study a number of analytical procedures are described to determine pharmaceuticals and personal care products (PPCPs) and their metabolites during sewage treatment. The work shows that PPCPs occur in sewage influent and are removed by various wastewater treatment processes. PPCPs include a wide range of chemicals such as prescription drugs as well as diagnostic agents, fragrances, sun-screen agents, and various other compounds commonly present in household items (e.g. detergents, cleaners, toothpastes etc.). During this study a number of PPCPs including painkillers (aspirin, ibuprofen), cholesterol control medication (clofibric acid), antibacterial agents (triclosan), musks (including galaxolide and tonalide), X-ray contrast media (diatrizoate), cancer treatment drugs (cyclophosphamide) and anti-depressant drugs (fluvoxamine) were investigated. Analysis was carried out using a number of techniques. Samples were extracted using solid phase extraction or liquid-liquid extraction and the extracts analysed using capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring or liquid chromatography mass spectrometry (LC-MS) or LC-MS-MS. The results obtained show that aspirin, clolibric acid, diatrozate, fluvoxamine and cyclophosphamide were not detected in any of the crude sewage or sewage effluent samples above the limit of detection of the applied methods. Ibuprofen was detected in all crude sewage samples as well as in all effluent samples with one exception. Removal of ibuprofen by the different STWs was generally between 80-100%, with the exception of one STW where removal was poor (14.4 to 44%). Triclosan was also detected in all crude sewage samples and in all sewage effluent samples. The highest concentration of triclosan detected was 3100 ng l(-1). A high removal efficiency was observed in effluent samples taken on two occasions (average removal 95.6%). The concentrations of musks detected in the crude sewage were generally low except for galaxolide and tonalide. The results from STW effluent samples showed significant removal of galaxolide (70-83% removal) except at one STW (STW 1) where removal was low (57% and 39%). Similar removal efficiencies for tonalide were achieved at these STWs (73-96%) except at STW 1 where removal was poor (53%).

We present experimental observations of coherent spin-population oscillations in a cold thermal, Bose gas of spin-1 23 Na atoms. The population oscillations in a multi-spatial-mode thermal gas have the same behavior as those observed in a single-spatial-mode antiferromagnetic spinor Bose Einstein condensate. We demonstrate this by showing that the two situations are described by the same dynamical equations, with a factor of two change in the spin-dependent interaction coefficient, which results from the change to particles with distinguishable momentum states in the thermal gas. We compare this theory to the measured spin population evolution after times up to a few hundreds of ms, finding quantitative agreement with the amplitude and period. We also measure the damping time of the oscillations as a function of magnetic field.Although Bose-Einstein condensates (BECs) are often thought of for sensitive measurements, their spatial coherence is not always necessary. Thermal atomic collisions are often mistakenly thought to be incoherent but, while keeping track of the spatial coherence is difficult, coherence can sometimes more easily be followed in the internal degrees of freedom. Thus, cold thermal clouds are often just as sensitive for use in spin measurements. In this work, we demonstrate collisionally-driven coherent spin population oscillations that can be interpreted as zero-momentum spin waves in a cold thermal cloud of spin-1 atoms. Such oscillations were previously only seen in the context of BECs [1-5] and two-atom, singlespatial-mode systems [6,7]. The spin oscillations that we observe in a highly multi-spatial-mode thermal gas are remarkable in that they can be described by a theory that is independent of the spatial degrees of freedom.Well-known examples of thermal spin systems that preserve internal spin states include optically-pumped dilute gases used for magnetometry [8] and spin-polarized noble gas imaging [9]. The spin polarization can be maintained even while the gas is trapped in glass cells, or by living tissues like lungs. Hydrogen masers are based on interrogating the free precession of a spin superposition of a thermal gas in a glass cell. Less well-known, collisionally-driven spin-wave effects were predicted in 1982 [10,11], and observations of such effects were reported soon thereafter in low-temperature spin-polarized hydrogen [12]. Bosonic and fermionic alkali pseudo-spin-1/2 systems have also been studied [13][14][15], and spin domain formation has been observed in these systems [16][17][18]. Due to the spindependent interaction that is absent in the pseudo-spin-1/2 system, a spin-1 gas is predicted to have additional interesting coherent collisional (spinor) dynamics which give rise to spin waves or population oscillations [19,20].The dynamics of spinor BECs have been widely investigated in spin-1 Na and Rb gases, as reviewed in Refs. [21,22]. Rb in the F = 1 state is ferromagnetic (spin-aligned collisions having the lowest energy), whereas Na is considered antiferromagnetic. Both o...