9 research outputs found
Long-range diatomic s + p potentials of heavy rare gases
We examine the long-range part of the rare-gas diatomic potentials that connect to the R{(n-1)p5ns}+R{(n-1)p5np} atomic states in the separated atom limit (n=3, 4, 5, and 6 for Ne, Ar, Kr, and Xe, respectively). We obtain our potentials by diagonalization of a Hamiltonian matrix containing the atomic energies and the electric dipole-dipole interaction, with experimentally determined parameters (atomic energies, lifetimes, transition wavelengths, and branching ratios) as input. Our numerical studies focus on Ne and Kr in this paper, but apply in principle to all other rare gases lacking hyperfine structure. These diatomic potentials are essential for applications in which homonuclear rare-gas pairs interact at large internuclear separations, greater than about 20 Bohr radii. Among such applications are the study of cold atomic collisions and photoassociative spectroscopy
Diffraction of a released bose-einstein condensate by a pulsed standing light wave
We study the diffraction of a released sodium Bose-Einstein condensate by a pulsed standing light wave. The width of the momentum distribution of the diffracted atoms exhibits strong oscillations as a function of the pulse duration, corresponding to periodic focusing and collimation of the condensate inside the standing light wave. Applications of this thick grating regime of diffraction to atom interferometry are discussed
Metastable neon collisions: anisotropy and scattering length
In this paper we investigate the effective scattering length of
spin-polarized Ne*. Due to its anisotropic electrostatic interaction, its
scattering length is determined by five interaction potentials instead of one,
even in the spin-polarized case, a unique property among the Bose condensed
species and candidates. Because the interaction potentials of Ne* are not known
accurately enough to predict the value of the scattering length, we investigate
the behavior of as a function of the five phase integrals corresponding to
the five interaction potentials. We find that the scattering length has five
resonances instead of only one and cannot be described by a simple gas-kinetic
approach or the DIS approximation. However, the probability for finding a
positive or large value of the scattering length is not enhanced compared to
the single potential case. The complex behavior of is studied by comparing
a quantum mechanical five-channel numerical calculation to simpler two-channel
models. We find that the induced dipole-dipole interaction is responsible for
coupling between the different |\Omega> states, resulting in an inhomogeneous
shift of the resonance positions and widths in the quantum mechanical
calculation as compared to the DIS approach. The dependence of the resonance
positions and widths on the input potentials turns out to be rather
straightforward. The existence of two bosonic isotopes of Ne* enables us to
choose the isotope with the most favorable scattering length for efficient
evaporative cooling towards the Bose-Einstein Condensation transition, greatly
enhancing the feasibility to reach this transition.Comment: 13pages, 8 eps figures, analytical model in section V has been
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Long-range diatomic s + p potentials of heavy rare gases
We examine the long-range part of the rare-gas diatomic potentials that connect to the R{(n-1)p5ns}+R{(n-1)p5np} atomic states in the separated atom limit (n=3, 4, 5, and 6 for Ne, Ar, Kr, and Xe, respectively). We obtain our potentials by diagonalization of a Hamiltonian matrix containing the atomic energies and the electric dipole-dipole interaction, with experimentally determined parameters (atomic energies, lifetimes, transition wavelengths, and branching ratios) as input. Our numerical studies focus on Ne and Kr in this paper, but apply in principle to all other rare gases lacking hyperfine structure. These diatomic potentials are essential for applications in which homonuclear rare-gas pairs interact at large internuclear separations, greater than about 20 Bohr radii. Among such applications are the study of cold atomic collisions and photoassociative spectroscopy
A high-intensity beam of Ne(3s) atoms with application to ultra-cold ionizations properties
We have developed a ``beam brightener'' in which several different laser cooling methods produce a highly monochromatic, unidirectional and intense beam of metastable Ne(3s;^3P_2) atoms. The beam brightener consists of four main stages. From an exited neon source we capture in a collimating section 5× 10^11 Ne(3s)/s from which ≈ 50 % is slowed to 100 m/s in a Zeeman slower. The final velocity distribution shows a width of 3.3 m/s uc(RMS,) corresponding to a temperature of 12 mK. A fraction of ≈ 25 % of these cold atoms is captured by a magneto-optic compressor and molded into a 0.7 mm uc(FWHM) wide atomic beam that contains up to 5× 10^10 Ne(3s)/s. The resulting density is 1.1× 10^9 Ne(3s)/cm^3. In the final step, a Doppler cooler is used to minimize the divergence of the beam to 10 mrad. This value will further improve once the Doppler cooler is replaced by a sub-Doppler cooler. We plan to use this ``bright beam'' to investigate the ionization probabilities in Ne(3s)+Ne(3s) collisions. Emphasis will be on the suppression of ionization when the atoms are spin-polarized. This has important implications for the possibilities of using metastable atoms for BEC-type experiments. Present adress: NIS
Measurement of force-assisted population accumulation in dark states
Atoms can be accumulated by velocity-selective coherent population trapping (VSCPT) in dark states of very highly monovelocity, resulting in very narrow distributions. The optical pumping process that permits the population accumulation proceeds by random walk in momentum space and is of limited eff iciency. Several authors have predicted that damping forces can enhance VSCPT in carefully chosen laser f ields. We present corroboration of this idea with measurements showing increased efficiency for VSCPT
Diffraction of a released bose-einstein condensate by a pulsed standing light wave
We study the diffraction of a released sodium Bose-Einstein condensate by a pulsed standing light wave. The width of the momentum distribution of the diffracted atoms exhibits strong oscillations as a function of the pulse duration, corresponding to periodic focusing and collimation of the condensate inside the standing light wave. Applications of this thick grating regime of diffraction to atom interferometry are discussed