752 research outputs found

    Collisional and molecular spectroscopy in an ultracold Bose-Bose mixture

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    The route toward a Bose-Einstein condensate of dipolar molecules requires the ability to efficiently associate dimers of different chemical species and transfer them to the stable rovibrational ground state. Here, we report on recent spectroscopic measurements of two weakly bound molecular levels and newly observed narrow d-wave Feshbach resonances. The data are used to improve the collisional model for the Bose-Bose mixture 41K87Rb, among the most promising candidates to create a molecular dipolar BEC.Comment: 13 pages, 3 figure

    Monetary Policy and Transmission Mechanisms: New Elements for an old Debate

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    This article begins by reviewing the current state of the arts in monetary transmission, focusing on the empirical evidence for the Chilean case. Then, it highlights two aspects that have not been given much attention in previous studies, namely the evolution of the monetary policy impact on output and prices over the past decade, and its breakdown by sector. A basic uniequational model is estimated, in order to study i) temporary shifts in the effectiveness of monetary policy and ii) shifts in regimes occurred in the late nineties. Then, VAR models are used—similar to those of previous studies—to analyze impulse-response functions. Finally, a comparative analysis is made on the impact of monetary policy on various productive sectors, for which output and price variables are incorporated into the traditional VAR model.

    Spectroscopy of Ultracold, Trapped Cesium Feshbach Molecules

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    We explore the rich internal structure of Cs_2 Feshbach molecules. Pure ultracold molecular samples are prepared in a CO_2-laser trap, and a multitude of weakly bound states is populated by elaborate magnetic-field ramping techniques. Our methods use different Feshbach resonances as input ports and various internal level crossings for controlled state transfer. We populate higher partial-wave states of up to eight units of rotational angular momentum (l-wave states). We investigate the molecular structure by measurements of the magnetic moments for various states. Avoided level crossings between different molecular states are characterized through the changes in magnetic moment and by a Landau-Zener tunneling method. Based on microwave spectroscopy, we present a precise measurement of the magnetic-field dependent binding energy of the weakly bound s-wave state that is responsible for the large background scattering length of Cs. This state is of particular interest because of its quantum-halo character.Comment: 15 pages, 12 figures, 4 table

    Ultracold atomic quantum gases far from equilibrium

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    We calculate the time evolution of a far-from-equilibrium initial state of a non-relativistic ultracold Bose gas in one spatial dimension. The non-perturbative approximation scheme is based on a systematic expansion of the two-particle irreducible effective action in powers of the inverse number of field components. This yields dynamic equations which contain direct scattering, memory and off-shell effects that are not captured in mean-field theory.Comment: 4 pages, Proc. Int. Conf. Strong and Electroweak Matter, SEWM 2006; Nucl. Phys. A, to be publishe

    Laser Intensity Dependence of Photoassociation in Ultracold Metastable Helium

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    Photoassociation of spin-polarized metastable helium to the three lowest rovibrational levels of the J=1, 0u+0_u^+ state asymptoting to 2s3s {}^{3}S1+2p3_{1}+2p {}^{3}P0_{0} is studied using a second-order perturbative treatment of the line shifts valid for low laser intensities, and two variants of a non-perturbative close-coupled treatment, one based upon dressed states of the matter plus laser system, and the other on a modified radiative coupling which vanishes asymptotically, thus simulating experimental conditions. These non-perturbative treatments are valid for arbitrary laser intensities and yield the complete photoassociation resonance profile. Both variants give nearly identical results for the line shifts and widths of the resonances and show that their dependence upon laser intensity is very close to linear and quadratic respectively for the two lowest levels. The resonance profiles are superimposed upon a significant background loss, a feature for this metastable helium system not present in studies of photoassociation in other systems, which is due to the very shallow nature of the excited state 0u+0_u^+ potential. The results for the line shifts from the close-coupled and perturbative calculations agree very closely at low laser intensities.Comment: 14 pages, 7 figures, title altered, text reduce

    Ecofeminism in the 21st Century

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    This paper considers the influence of ecofeminism on policy concerning gender (in)equality and the environment during the past 20 years. It reviews the broad contours of the ecofeminist debate before focusing on the social construction interpretation of women's relationship with the environment. It will argue that there have been substantial policy shifts in Europe and the UK in both the environmental and equalities fields, and that this is in part a result of lobbying at a range of scales by groups informed by ecofeminist debates. Nevertheless, the paper cautions that these shifts are largely incremental and operate within existing structures, which inevitably limit their capacity to create change. As policy addresses some of the concerns highlighted by ecofeminism, academic discourse and grass roots activity have been moving on to address other issues, and the paper concludes with a brief consideration of contemporary trajectories of ecofeminism and campaigning on issues that link women's, feminist and environment concerns

    Coherent Control of Isotope Separation in HD+ Photodissociation by Strong Fields

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    The photodissociation of the HD+ molecular ion in intense short- pulsed linearly polarized laser fields is studied using a time- dependent wave-packet approach where molecular rotation is fully included. We show that applying a coherent superposition of the fundamental radiation with its second harmonic can lead to asymmetries in the fragment angular distributions, with significant differences between the hydrogen and deuterium distributions in the long wavelength domain where the permanent dipole is most efficient. This effect is used to induce an appreciable isotope separation.Comment: Physical Review Letters, 1995 (in press). 4 pages in revtex format, 3 uuencoded figures. Full postcript version available at: http://chemphys.weizmann.ac.il/~charron/prl.ps or ftp://scipion.ppm.u-psud.fr/coherent.control/prl.p

    Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense Rubidium and Cesium Vapor

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    Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers are 290 MHz for Rb; 2500 MHz for Cs.Comment: submitted to Physical Review Letters, text + 3 figure
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