Magnetic field control of elastic scattering in a cold gas of fermionic lithium atoms

We study elastic collisions in an optically trapped spin mixture of fermionic lithium atoms in the presence of magnetic fields up to 1.5kG by measuring evaporative loss. Our experiments confirm the expected magnetic tunability of the scattering length by showing the main features of elastic scattering according to recent calculations. We measure the zero crossing of the scattering length that is associated with a predicted Feshbach resonance at 530(3)G. Beyond the resonance we observe the expected large cross section in the triplet scattering regime

Theory of semi-ballistic wave propagation

Wave propagation through waveguides, quantum wires or films with a modest amount of disorder is in the semi-ballistic regime when in the transversal direction(s) almost no scattering occurs, while in the long direction(s) there is so much scattering that the transport is diffusive. For such systems randomness is modelled by an inhomogeneous density of point-like scatterers. These are first considered in the second order Born approximation and then beyond that approximation. In the latter case it is found that attractive point scatterers in a cavity always have geometric resonances, even for Schr\"odinger wave scattering. In the long sample limit the transport equation is solved analytically. Various geometries are considered: waveguides, films, and tunneling geometries such as Fabry-P\'erot interferometers and double barrier quantum wells. The predictions are compared with new and existing numerical data and with experiment. The agreement is quite satisfactory.Comment: 24 pages Revtex; 10 figure

Sympathetic Cooling of Lithium by Laser-cooled Cesium

We present first indications of sympathetic cooling between two neutral, optically trapped atomic species. Lithium and cesium atoms are simultaneously stored in an optical dipole trap formed by the focus of a CO$_2$ laser, and allowed to interact for a given period of time. The temperature of the lithium gas is found to decrease when in thermal contact with cold cesium. The timescale of thermalization yields an estimate for the Li-Cs cross-section.Comment: 4 pages, proceedings of ICOLS 200

The Iranian Hostage Crisis and the Iran-U.S. Claims Tribunal: Implications for International Dispute Resolution and Diplomacy

This is the twenty-fifth anniversary of what has become known as the Iranian Hostage Crisis. We shall look back on those events in order to point to possible issues, lessons and solutions for the future

Mixture of ultracold lithium and cesium atoms in an optical dipole trap

We present the first simultaneous trapping of two different ultracold atomic species in a conservative trap. Lithium and cesium atoms are stored in an optical dipole trap formed by the focus of a CO$_2$ laser. Techniques for loading both species of atoms are discussed and observations of elastic and inelastic collisions between the two species are presented. A model for sympathetic cooling of two species with strongly different mass in the presence of slow evaporation is developed. From the observed Cs-induced evaporation of Li atoms we estimate a cross section for cold elastic Li-Cs collisions.Comment: 10 pages 9 figures, submitted to Appl. Phys. B; v2: Corrected evaporation formulas and some postscript problem