In the atomic Bose-Einstein condensate, the interactions that bring a binary atom system to an intermediate state molecule in the Feshbach resonance create a second condensate component of molecules. The atomic and molecular condensates coherently exchange pairs of atoms. We discuss a signature of the coherent intercondensate exchange: Josephson-like oscillations of the atomic and molecular populations in response to a sudden change of the energy detuning. The dependence of the many-body ground state energy on volume suggests that the on-resonant ground state is a dilute condensate with the liquidlike property of a self-determined density. PACS numbers: 03.75.Fi, 05.30.Jp, 32.80.Pj, 67.90. + z As dilute gases, the atomic Bose-Einstein condensates [1-3] are amenable to atomic manipulation techniques. As superfluids [4], these dilute condensates exhibit an unusual degree of flexibility, promising novel studies of macroscopic quantum coherence. For instance, the notion that external fields can alter the interatomic interactions [5] suggests the study of condensates with interparticle interactions that can be experimentally controlled [6]. Signatures of one of the proposed schemes, the low energy Feshbach resonance [7], have been observed recently [8].In this Letter, we point out that this resonance affects the condensate system more profoundly than altering an effective interparticle interaction: the molecules, formed in the intermediate state of the binary atom resonance, occupy a second condensate component. The atomic and molecular condensates interact in part by coherently exchanging pairs of atoms, implying interesting and unusual properties. Below, we discuss two examples: (i) The molecular condensate, even if it is small in the off-resonant regime, can reveal its presence by means of Josephson-like oscillations of the atomic and molecular populations in response to a sudden change of the detuning. (ii) Close to resonance, the coherent intercondensate tunneling binds the dilute manybody Bose-Einstein condensate (BEC) to a system with the liquidlike property of a self-determined density.In the low energy Feshbach resonance, the hyperfine interaction, V hf , rearranges the spins of two alkali atoms interacting in an external magnetic field B, bringing them to an intermediate quasibound molecular state. In this process, a valence electron spin is "flipped" which, in the magnetic field, raises the continuum of the intermediate spin state jS 0 ͘ by an amount D͑B͒, relative to the continuum of the initial binary atom spin state jS͘. At a resonant magnetic field B B m , the jS͘ continuum lines up with the bound state m of the jS 0 ͘ interatomic potential. Near the resonance, the energy difference e of the initial and intermediate states, which we call "detuning," varies with magnetic field, e ഠ ͑≠D͞≠B͒ 3 ͓B 2 B m ͔. The amplitude of the resonant process is characterized by a ͗S 0 jV hf jS͘ 3 R d 3 r w ‫ء‬ m ͑r͒w͑r͒, where w m denotes the vibrational wave function of the m state and w the continuum (jS͘) wave function...

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Extensive systematizations of theoretical and experimental nuclear densities and of optical potential strengths extracted from heavy-ion elastic scattering data analyses at low and intermediate energies are presented. The energy dependence of the nuclear potential is accounted for within a model based on the nonlocal nature of the interaction. The systematics indicates that the heavy-ion nuclear potential can be described in a simple global way through a double-folding shape, which basically depends only on the density of nucleons of the partners in the collision. The possibility of extracting information about the nucleon-nucleon interaction from the heavy-ion potential is investigated.

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