Three-body decay of a rubidium Bose-Einstein condensate

We have measured the three-body decay of a Bose-Einstein condensate of rubidium ($^{87}$Rb) atoms prepared in the doubly polarized ground state $F=m_F=2$. Our data are taken for a peak atomic density in the condensate varying between $2\times 10^{14}$ cm$^{-3}$ at initial time and $7\times 10^{13}$ cm$^{-3}$, 16 seconds later. Taking into account the influence of the uncondensed atoms onto the decay of the condensate, we deduce a rate constant for condensed atoms $L=1.8 (\pm 0.5) \times 10^{-29}$ cm$^{6}$s$^{-1}$. For these densities we did not find a significant contribution of two-body processes such as spin dipole relaxation.Comment: 14 pages, 4 figure

Lead in the marine environment: concentrations and effects on invertebrates

Lead (Pb) is a non-essential metal naturally present in the environment and often complexed with other elements (e.g., copper, selenium, zinc). This metal has been used since ancient Egypt and its extraction has grown in the last centuries. It has been used until recently as a fuel additive and is currently used in the production of vehicle batteries, paint, and plumbing. Marine ecosystems are sinks of terrestrial contaminations; consequently, lead is detected in oceans and seas. Furthermore, lead is not biodegradable. It remains in soil, atmosphere, and water inducing multiple negative impacts on marine invertebrates (key species in trophic chain) disturbing ecological ecosystems. This review established our knowledge on lead accumulation and its effects on marine invertebrates (Annelida, Cnidaria, Crustacea, Echinodermata, and Mollusca). Lead may affect different stages of development from fertilization to larval development and can also lead to disturbance in reproduction and mortality. Furthermore, we discussed changes in the seawater chemistry due to Ocean Acidification, which can affect the solubility, speciation, and distribution of the lead, increasing potentially its toxicity to marine invertebrates

Frequencies and Damping rates of a 2D Deformed Trapped Bose gas above the Critical Temperature

We derive the equation of motion for the velocity fluctuations of a 2D deformed trapped Bose gas above the critical temperature in the hydrodynamical regime. From this equation, we calculate the eigenfrequencies for a few low-lying excitation modes. Using the method of averages, we derive a dispersion relation in a deformed trap that interpolates between the collisionless and hydrodynamic regimes. We make use of this dispersion relation to calculate the frequencies and the damping rates for monopole and quadrupole mode in both the regimes. We also discuss the time evolution of the wave packet width of a Bose gas in a time dependent as well as time independent trap.Comment: 13 pages, latex fil

Finite-temperature simulations of the scissors mode in Bose-Einstein condensed gases

The dynamics of a trapped Bose-condensed gas at finite temperatures is described by a generalized Gross-Pitaevskii equation for the condensate order parameter and a semi-classical kinetic equation for the thermal cloud, solved using $N$-body simulations. The two components are coupled by mean fields as well as collisional processes that transfer atoms between the two. We use this scheme to investigate scissors modes in anisotropic traps as a function of temperature. Frequency shifts and damping rates of the condensate mode are extracted, and are found to be in good agreement with recent experiments.Comment: 4 pages, 3 figure

Precision Feshbach spectroscopy of ultracold Cs-2

We have observed and located more than 60 magnetic field-induced Feshbach resonances in ultracold collisions of ground-state Cs-133 atoms. Multiple extremely weak Feshbach resonances associated with g-wave molecular states are detected through variations in the radiative collision cross sections. The Feshbach spectroscopy allows us to determine the interactions between ultracold cesium atoms and the molecular energy structure near the dissociation continuum with unprecedented precision. Our work not only represents a very successful collaboration of experimental and theoretical efforts, but also provides essential information for cesium Bose-Einstein condensation, Cs-2 molecules, and atomic clock experiments