Formation of Pairing Fields in Resonantly Coupled Atomic and Molecular Bose-Einstein Condensates

In this paper, we show that pair-correlations may play an important role in the quantum statistical properties of a Bose-Einstein condensed gas composed of an atomic field resonantly coupled with a corresponding field of molecular dimers. Specifically, pair-correlations in this system can dramatically modify the coherent and incoherent transfer between the atomic and molecular fields.Comment: 4 pages, 4 figure

Stationary solutions of the one-dimensional nonlinear Schroedinger equation: II. Case of attractive nonlinearity

All stationary solutions to the one-dimensional nonlinear Schroedinger equation under box or periodic boundary conditions are presented in analytic form for the case of attractive nonlinearity. A companion paper has treated the repulsive case. Our solutions take the form of bounded, quantized, stationary trains of bright solitons. Among them are two uniquely nonlinear classes of nodeless solutions, whose properties and physical meaning are discussed in detail. The full set of symmetry-breaking stationary states are described by the $C_{n}$ character tables from the theory of point groups. We make experimental predictions for the Bose-Einstein condensate and show that, though these are the analog of some of the simplest problems in linear quantum mechanics, nonlinearity introduces new and surprising phenomena.Comment: 11 pages, 9 figures -- revised versio

Bose-enhanced chemistry: Amplification of selectivity in the dissociation of molecular Bose-Einstein condensates

We study the photodissociation chemistry of a quantum degenerate gas of bosonic triatomic $ABC$ molecules, assuming two open rearrangement channels ($AB+C$ or $A+BC$). The equations of motion are equivalent to those of a parametric multimode laser, resulting in an exponential buildup of macroscopic mode populations. By exponentially amplifying a small differential in the single-particle rate-coefficients, Bose stimulation leads to a nearly complete selectivity of the collective $N$-body process, indicating a novel type of ultra-selective quantum degenerate chemistry.Comment: 5 pages, 3 figure

Three-body recombination in Bose gases with large scattering length

An effective field theory for the three-body system with large scattering length is applied to three-body recombination to a weakly-bound s-wave state in a Bose gas. Our model independent analysis demonstrates that the three-body recombination constant alpha is not universal, but can take any value between zero and 67.9 \hbar a^4/m, where a is the scattering length. Other low-energy three-body observables can be predicted in terms of a and alpha. Near a Feshbach resonance, alpha should oscillate between those limits as the magnetic field B approaches the point where a -> infinity. In any interval of B over which a increases by a factor of 22.7, alpha should have a zero.Comment: 8 pages, RevTex, 3 postscript figures, uses epsf.sty, rotate.sty, references added, discussion improve

Microscopic Dynamics in a Strongly Interacting Bose-Einstein Condensate

An initially stable 85Rb Bose-Einstein condensate (BEC) was subjected to a carefully controlled magnetic field pulse in the vicinity of a Feshbach resonance. This pulse probed the strongly interacting regime for the condensate, with calculated values for the diluteness parameter (na^3) ranging from 0.01 to 0.5. The field pulse was observed to cause loss of atoms from the condensate on remarkably short time scales (>=10 microsec). The dependence of this loss on magnetic field pulse shape and amplitude was measured. For triangular pulses shorter than 1 ms, decreasing the pulse length actually increased the loss, until extremely short time scales (a few tens of microseconds) were reached. Such time scales and dependencies are very different from those expected in traditional condensate inelastic loss processes, suggesting the presence of new microscopic BEC physics.Comment: 4 pages in latex2E, 4 eps figures; revised Fig.1, revised scatt.lengths, added discussion, new refs., resubmitted to PR

High-precision calculations of dispersion coefficients, static dipole polarizabilities, and atom-wall interaction constants for alkali-metal atoms

The van der Waals coefficients for the alkali-metal atoms from Na to Fr interacting in their ground states, are calculated using relativistic ab initio methods. The accuracy of the calculations is estimated by also evaluating atomic static electric dipole polarizabilities and coefficients for the interaction of the atoms with a perfectly conducting wall. The results are in excellent agreement with the latest data from ultra-cold collisions and from studies of magnetic field induced Feshbach resonances in Na and Rb. For Cs we provide critically needed data for ultra-cold collision studies

Elastic and inelastic collisions of 6Li in magnetic and optical traps

We use a full coupled channels method to calculate collisional properties of magnetically or optically trapped ultracold 6Li. The magnetic field dependence of the s-wave scattering lengths of several mixtures of hyperfine states are determined, as are the decay rates due to exchange collisions. In one case, we find Feshbach resonances at B=0.08 T and B=1.98 T. We show that the exact coupled channels calculation is well approximated over the entire range of magnetic fields by a simple analytical calculation.Comment: 4 pages revtex including 4 figures, submitted to PR

Feshbach-Stimulated Photoproduction of a Stable Molecular Condensate

Photoassociation and the Feshbach resonance are, in principle, feasible means for creating a molecular Bose-Einstein condensate from an already-quantum-degenerate gas of atoms; however, mean-field shifts and irreversible decay place practical constraints on the efficient delivery of stable molecules using either mechanism alone. We therefore propose Feshbach-stimulated Raman photoproduction, i.e., a combination of magnetic and optical methods, as a viable means to collectively convert degenerate atoms into a stable molecular condensate with near-unit efficiency.Comment: 5 pages, 3 figures, 1 table; v3 includes few-level diagram of scheme, and added discussion; transferred to PR

Very high precision bound state spectroscopy near a 85^{85}Rb Feshbach resonance

We precisely measured the binding energy of a molecular state near the Feshbach resonance in a $^{85}$Rb Bose-Einstein condensate (BEC). Rapid magnetic field pulses induced coherent atom-molecule oscillations in the BEC. We measured the oscillation frequency as a function of B-field and fit the data to a coupled-channels model. Our analysis constrained the Feshbach resonance position [155.041(18) G], width [10.71(2) G], and background scattering length [-443(3) a$_0$] and yielded new values for $v_{DS}$, $v_{DT}$, and $C_6$. These results improved our estimate for the stability condition of an attractive BEC. We also found evidence for a mean-field shift to the binding energy.Comment: 5 pages, 2 figures, submitted to PR