Thermodynamic properties of matter generally depend on the details of interactions between its constituent parts. However, in a unitary Fermi gas where the scattering length diverges, thermodynamics is determined through universal functions that depend only on the particle density and temperature. By using only the general form of the equation of state and the equation of force balance, we measured the local internal energy of the trapped gas as a function of these parameters. Other universal functions, such as those corresponding to the Helmholtz free energy, chemical potential, and entropy, were calculated through general thermodynamic relations. The critical parameters were also determined at the superfluid transition temperature. These results apply to all strongly interacting fermionic systems, including neutron stars and nuclear matter.

Ultracold sodium molecules were produced from an atomic Bose-Einstein condensate by ramping an applied magnetic field across a Feshbach resonance. More than 10(5) molecules were generated with a conversion efficiency of approximately 4%. Using laser light resonant with an atomic transition, the remaining atoms could be selectively removed, preventing fast collisional relaxation of the molecules. Time-of-flight analysis of the pure molecular sample yielded an instantaneous phase-space density greater than 20.

We observe coherent resonant coupling of optical whispering-gallery modes in fluorescence from dye doped polymer bispheres with diameters ranging from 2 to 5 mm. By monitoring the frequencies of fluorescence peaks of individual spheres, we sort out two spheres with appropriate size matching and bring them into contact. Wave optics calculation also gives good agreement with the experiment. By taking into account harmonic coupling of the whispering-gallery modes, the obtained features of normal mode splitting are well explained by the tight-binding photon picture. [S0031-9007(99)09349-7] PACS numbers: 42.60.DaManipulation of light path in micrometer length scale has recently attracted considerable attention from both fundamental and application points of view. Conventionally, the manipulation is based on the photonic crystal concept [1][2][3]. In photonic crystals, which have periodic modulation of the refractive index, propagation of the light wave is governed by a weak potential. Correspondingly, such an approach can be referred to as a nearly free photon approach analogous to the nearly free electron approach in band theory. Alternatively the micromanipulation of light can be achieved by exploring the possibility of confining the light in a small unit of the wavelength size. Light propagates through the system of such units due to the coupling between the nearest neighbors. This approach is referred to as the tight-binding photon approach [4]. Within the tight-binding photon approach we can guide the optical waves by connecting the units in the arbitrarily shaped microstructures.The microspheres are the most natural choice of the unit to be employed in the tight-binding photon device. It is known that a dielectric sphere acts as a unique optical microcavity which has very long photon storage time within a small mode volume [5][6][7][8]. In particular, Q factors of the order of 10 10 have been observed for whispering gallery modes (WGM's) in quartz spheres with a diameter of several tens of micrometers [9-13], and the mode structure of a pair of these large spheres in contact has been studied [14]. However, in order to explore the feasibility of micromanipulation of light, one has to confirm the existence of the coherent coupling between spheres of the size of a few times of optical wavelength. Lorenz-Mie theory predicts long photon lifetime even for small spheres, giving, for example, nearly 30 ps for a 4 mm sphere with a refractive index of 1.59. This has allowed one to propose such relatively small spheres to be employed as "photonic atoms" [15] for the tight-binding scheme. However, the coherent coupling between two adjacent microspheres of such size range have not been realized until now. The coherent coupling results in the splitting of the corresponding WGM's and is a manifestation of the well-known phenomena of the normal mode splitting (NMS) in coupled harmonic oscillators. However, although some attempts have been made [16], NMS has not yet been observed because of the difficulty in the precise size con...