1,077 research outputs found

    Regulation of Recombinant DNA Research: A Comparative Study

    Get PDF

    Molecular Fine Structure from Water Window X-rays

    Get PDF
    Postprint (published version

    Collective Oscillations of an Imbalanced Fermi Gas: Axial Compression Modes and Polaron Effective Mass

    Full text link
    We investigate the low-lying compression modes of a unitary Fermi gas with imbalanced spin populations. For low polarization, the strong coupling between the two spin components leads to a hydrodynamic behavior of the cloud. For large population imbalance we observe a decoupling of the oscillations of the two spin components, giving access to the effective mass of the Fermi polaron, a quasi-particle composed of an impurity dressed by particle-hole pair excitations in a surrounding Fermi sea. We find m/m=1.17(10)m^*/m=1.17(10), in agreement with the most recent theoretical predictions.Comment: 4 pages, 4 figures, submitted to PR

    Expansion of a lithium gas in the BEC-BCS crossover

    Full text link
    We report on experiments in 6^6Li Fermi gases near Feshbach resonances. A broad s-wave resonance is used to form a Bose-Einstein condensate of weakly bound 6^6Li2_2 molecules in a crossed optical trap. The measured molecule-molecule scattering length of 17060+100170^{+100}_{-60} nm at 770 G is found in good agreement with theory. The expansion energy of the cloud in the BEC-BCS crossover region is measured. Finally we discuss the properties of p-wave Feshbach resonances observed near 200 Gauss and new s-wave resonances in the heteronuclear 6^6Li- 7^7Li mixture.Comment: 10 pages, 3 figures, Proceedings of ICAP 200

    Attosecond Streaking in the Water Window: A New Regime of Attosecond Pulse Characterization

    Full text link
    We report on the first streaking measurement of water-window attosecond pulses generated via high harmonic generation, driven by sub-2-cycle, CEP-stable, 1850 nm laser pulses. Both the central photon energy and the energy bandwidth far exceed what has been demonstrated thus far, warranting the investigation of the attosecond streaking technique for the soft X-ray regime and the limits of the FROGCRAB retrieval algorithm under such conditions. We also discuss the problem of attochirp compensation and issues regarding much lower photo-ionization cross sections compared with the XUV in addition to the fact that several shells of target gases are accessed simultaneously. Based on our investigation, we caution that the vastly different conditions in the soft X-ray regime warrant a diligent examination of the fidelity of the measurement and the retrieval procedure.Comment: 14 Pages, 12 figure

    Experimental Study of the BEC-BCS Crossover Region in Lithium 6

    Get PDF
    We report Bose-Einstein condensation of weakly bound 6^6Li2_2molecules in a crossed optical trap near a Feshbach resonance. We measure a molecule-molecule scattering length of17060+100170^{+100}_{-60} nm at 770 G, in good agreement with theory.We study the expansion of the cloud in the BEC-BCS crossoverregion.Comment: 4 pages, 3 figures, submitted to PR

    Bose-Einstein condensates in a double well: mean-field chaos and multi-particle entanglement

    Full text link
    A recent publication [Phys. Rev. Lett. 100, 140408 (2008)] shows that there is a relation between mean-field chaos and multi-particle entanglement for BECs in a periodically shaken double well. 'Schrodinger-cat' like mesoscopic superpositions in phase-space occur for conditions for which the system displays mean-field chaos. In the present manuscript, more general highly-entangled states are investigated. Mean-field chaos accelerates the emergence of multi-particle entanglement; the boundaries of stable regions are particularly suited for entanglement generation.Comment: 5 Pages, 5 jpg-figures, to be published in the proceedings of the LPHYS0
    corecore