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

Metastable neon collisions: anisotropy and scattering length

In this paper we investigate the effective scattering length $a$ 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 $a$ 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 $a$ 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 remove

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