All-Optical Production of a Degenerate Fermi Gas

We achieve degeneracy in a mixture of the two lowest hyperfine states of $^6$Li by direct evaporation in a CO$_2$ laser trap, yielding the first all-optically produced degenerate Fermi gas. More than $10^5$ atoms are confined at temperatures below $4 \mu$K at full trap depth, where the Fermi temperature for each state is $8 \mu$K. This degenerate two-component mixture is ideal for exploring mechanisms of superconductivity ranging from Cooper pairing to Bose condensation of strongly bound pairs.Comment: 4 pgs RevTeX with 2 eps figs, to be published in Phys. Rev. Let

The bottom mixed layer depth as an indicator of subsurface Chlorophyll a distribution

Acknowledgements The authors thank Marine Scotland Science for providing the CTD data. Financial support This research has been supported by a MarCRF (Marine Collaboration Research Forum, jointly sponsored by the University of Aberdeen and Marine Scotland Science) PhD grant awarded to Arianna Zampollo.Peer reviewedPublisher PD

The Cooperative Participatory Evaluation of Renewable Technologies on Ecosystem Services (CORPORATES)

Publisher PD

Creation of ultracold molecules from a Fermi gas of atoms

Since the realization of Bose-Einstein condensates (BEC) in atomic gases an experimental challenge has been the production of molecular gases in the quantum regime. A promising approach is to create the molecular gas directly from an ultracold atomic gas; for example, atoms in a BEC have been coupled to electronic ground-state molecules through photoassociation as well as through a magnetic-field Feshbach resonance. The availability of atomic Fermi gases provides the exciting prospect of coupling fermionic atoms to bosonic molecules, and thus altering the quantum statistics of the system. This Fermi-Bose coupling is closely related to the pairing mechanism for a novel fermionic superfluid proposed to occur near a Feshbach resonance. Here we report the creation and quantitative characterization of exotic, ultracold $^{40}$K$_2$ molecules. Starting with a quantum degenerate Fermi gas of atoms at T < 150 nanoKelvin we scan over a Feshbach resonance to adiabatically create over a quarter million trapped molecules, which we can convert back to atoms by reversing the scan. The small binding energy of the molecules is controlled by detuning from the Feshbach resonance and can be varied over a wide range. We directly detect these weakly bound molecules through rf photodissociation spectra that probe the molecular wavefunction and yield binding energies that are consistent with theory

Resonant control of elastic collisions in an optically trapped Fermi gas of atoms

We have loaded an ultracold gas of fermionic atoms into a far off resonance optical dipole trap and precisely controlled the spin composition of the trapped gas. We have measured a magnetic-field Feshbach resonance between atoms in the two lowest energy spin-states, |9/2, -9/2> and |9/2, -7/2>. The resonance peaks at a magnetic field of 201.5 plus or minus 1.4 G and has a width of 8.0 plus or minus 1.1 G. Using this resonance we have changed the elastic collision cross section in the gas by nearly 3 orders of magnitude.Comment: 4 pages, 3 figure

Effects of Expert Testimony and Interrogation Tactics on Perceptions of Confessions

Evidence obtained through the process of interrogation is frequently undermined by what can be perceived as overzealous interrogation tactics. Although the majority of psychologically oriented tactics are legally permissible, they nonetheless contribute to innocent suspects confessing to crimes they did not commit. The present study examined the effect of expert testimony and interrogation tactics on perceptions of a confession. 182 undergraduates read a transcript of a homicide trial that varied based on interrogation tactic: implicit threat of punishment (maximization) or leniency (minimization) and expert witness testimony (presence or absence of expert testimony). Analysis indicated that the type of interrogation tactic used in obtaining the confession affected participants\u27 perceptions of the coerciveness of the interrogation process

Ultrastable CO2 Laser Trapping of Lithium Fermions

We demonstrate an ultrastable CO2 laser trap that provides tight confinement of neutral atoms with negligible optical scattering and minimal laser-noise- induced heating. Using this method, fermionic 6Li atoms are stored in a 0.4 mK deep well with a 1/e trap lifetime of 300 sec, consistent with a background pressure of 10^(-11) Torr. To our knowledge, this is the longest storage time ever achieved with an all-optical trap, comparable to the best reported magnetic traps.Comment: 4 pages using REVTeX, 1 eps figur