Hydrodynamic excitations of trapped dipolar fermions

A single-component Fermi gas of polarized dipolar particles in a harmonic trap can undergo a mechanical collapse due to the attractive part of the dipole-dipole interaction. This phenomenon can be conveniently manipulated by the shape of the external trapping potential. We investigate the signatures of the instability by studying the spectrum of low-lying collective excitations of the system in the hydrodynamic regime. To this end, we employ a time-dependent variational method as well as exact numerical solutions of the hydrodynamic equations of the system.Comment: 4 pages, 2 eps figures, final versio

Laser cooling of a trapped two-component Fermi gas

The collective Raman cooling of a trapped two-component Fermi gas is analyzed. We develop the quantum master equation that describes the collisions and the laser cooling, in the festina lente regime, where the heating due to photon reabsorption can be neglected. The numerical results based on Monte Carlo simulations show, that three-dimensional temperatures of the order of 0.008 T_F can be achieved. We analyze the heating related to the background losses, and conclude that our laser-cooling scheme can maintain the temperature of the gas without significant additional losses. Finally we derive an analytic expression for the temperature of a trapped Fermi gas heated by background collisions, that agrees very well with the data obtained from the numerical simulation.Comment: 5 pages, 3 figure

Crossovers in Unitary Fermi Systems

Universality and crossover is described for attractive and repulsive interactions where, respectively, the BCS-BEC crossover takes place and a ferromagnetic phase transition is claimed. Crossovers are also described for optical lattices and multicomponent systems. The crossovers, universal parameters and phase transitions are described within the Leggett and NSR models and calculated in detail within the Jastrow-Slater approximation. The physics of ultracold Fermi atoms is applied to neutron, nuclear and quark matter, nuclei and electrons in solids whenever possible. Specifically, the differences between optical lattices and cuprates is discussed w.r.t. antiferromagnetic, d-wave superfluid phases and phase separation.Comment: 50 pages, 15 figures. Contribution to Lecture Notes in Physics "BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge

Decay of mass-separated Tl190 and Hg190

Radioactive sources containing Tl190 and Hg190 have been produced and mass separated with the University Isotope Separator on line to the Oak Ridge isochronous cyclotron. Multiscaled spectra of γ rays, x rays, conversion electrons, and positrons were obtained, and γ-γ and γ-x-ray coincidences were measured. Two isomers in Tl190 decay have half-lives of 2.6 ± 0.3 min (2-) and 3.7 ± 0.3 min (7+). From β decay endpoint energies the 7+ and 2- isomers lie within 0.1 MeV of each other, but which is the ground state was not determined. Both isomers have ground-state QEC values of approximately 7 MeV. The 2- level undergoes β decay primarily to the 2+ states at 416.4 and 1099.9 keV in Hg190, while the decay of the 7+ isomer feeds a number of different states with spins ranging from 5 to 9. We observed the 5-, 7-, and 9- members of the previously identified structure of negative-parity states resulting from coupling of a rotation-aligned i132 neutron with 3p32 and 2f52 neutrons. Some additional states having decays consistent with (6-) and (8-) assignments perhaps are candidates for less aligned members of the 13/2+ band coupled with p32 and f52 neutrons. The 20-min Hg190 isotope decays approximately 65% of the time to a level at 171.5 keV, thus making it difficult to study other levels in Au190. Four new states in Au190 were definitely established, while several new ones were suggested by the present work. The populated levels are predominantly low spin and are fairly closely spaced. The logft value for the transition to the 171.5 keV level is 5.7, so it is likely that this state has a spin and parity of 1+. RADIOACTIVITY Tl190, Tlm190, Hg190 [from Ta, W(O16,xp+yn), E=143,124 MeV]; mass-separated radioactivities. Measured T12, Eγ, Iγ, Ice, Eβ, γγ coin, γx coin. Deduced logft, Q. Hg190, Au190 deduced levels, J, π, ICC, Λ. © 1976 The American Physical Society

Nomenclature - Formal reports, proposals, and opinion

Formal proposals to conserve or protect fungal names as well as proposals to amend the International Code of Nomenclature of immediate interest to mycologists are now published concurrently in Mycotaxon and Taxon. Conservation proposals include Prop. 1918 (to conserve the name Dermatocarpon bucekii against Placidium steineri), Prop. 1919 (to conserve the name Lactarius with a conserved type), Prop. 1926 (to conserve the name Cladia against Heterodea, and Prop.1927 (to conserve the name Agaricus rachodes with that spelling). Props. 117-119 to amend the Code ask for pre-publication deposit of nomenclatural information in a recognized repository for valid publication of fungal names

On-line mass separator investigation of the new isotope 2.9-sec I116

Using on-line mass separation I116 has been identified and its half-life determined to be 2.91 0.15 sec. The activity was produced by the Rh103(O16, 3n)I116 reaction and by the decay of 57-sec Xe116. The I116 decays primarily to the ground state of Te116 and also to excited states at 678.9 and 1219.1 keV. From positron measurements, a decay energy of QEC=7.710.20 MeV is assigned to I116. rays of 540.2 and 678.9 keV are observed in this decay and are assigned to depopulate levels in Te116 at 1219.1 and 678.9 keV, respectively. The former is a new level with a probable spin-parity of either 2+ or 0+. From the logft values, a spinparity assignment of 1+ is deduced for the ground state of I116, which is interpreted to have a configuration of [(d52)(d32)]. A decay energy of QEC=4.340.20 MeV observed from activity produced by the Pd104 + O16 reaction is assigned to Xe116. NUCLEAR REACTIONS Rh103(O16, 3n), E=83 MeV; Pd104(O16, 4n) and Pd104(O16,p 3n), E=91 MeV. Natural Rh targets and enriched Pd targets. RADIOACTIVITY I116, Xe116; measured E, I, T12(), T12(+), +- coin., + end point; Te116 deduced levels, J, , logft; I116 deduced ground state J, , logft; Ge(Li) detectors and plastic scintillators; mass separated sources. © 1976 The American Physical Society