140 research outputs found

    Dynamics of ultracold dipolar particles in a confined geometry and tilted fields

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    We develop a collisional formalism adapted for the dynamics of ultracold dipolar particles in a confined geometry and in fields tilted relative to the confinement axis. Using tesseral harmonics instead of the usual spherical harmonics to expand the scattering wavefunction, we recover a good quantum number ξ=±1\xi = \pm 1 which is conserved during the collision. We derive the general expression of the dipole-dipole interaction in this convenient basis set as a function of the polar and azimuthal angles of the fields. We apply the formalism to the collision of fermionic and bosonic polar KRb molecules in a tilted electric field and in a one-dimensional optical lattice. The presence of a tilted field drastically changes the magnitude of the reactive and inelastic rates as well as the inelastic threshold properties at vanishing collision energies. Setting an appropriate strength of the confinement for the fermionic system, we show that the ultracold particles can even further reduce their kinetic energy by inelastic excitation to higher states of the confinement trap.Comment: 13 page

    Theory of long-range ultracold atom-molecule photoassociation

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    The creation of ultracold molecules is currently limited to diatomic species. In this letter we present a theoretical description of the photoassociation of ultracold atoms and molecules to create ultracold excited triatomic molecules, thus being a novel example of light-assisted ultracold chemical reaction. The calculation of the photoassociation rate of ultracold Cs atoms with ultracold Cs2_2 molecules in their rovibrational ground state is reported, based on the solution of the quantum dynamics involving the atom-molecule long-range interactions, and assuming a model potential for the short-range physics. The rate for the formation of excited Cs3_3 molecules is predicted to be comparable with currently observed atom-atom photoassociation rates. We formulate an experimental proposal to observe this process relying on the available techniques of optical lattices and standard photoassociation spectroscopy.Comment: 5 pages, 3 figure

    Proposal for laser-cooling of rare-earth ions

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    The efficiency of laser-cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser-cooling of singly-ionized erbium Er+^+ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er+^+, using a combination of \textit{ab initio} and least-square-fitting techniques. We identify five weak closed transitions suitable for laser-cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes. We expect our detailed study on Er+^+ to give a good insight into laser-cooling of neighboring ions like Dy+^+.Comment: 5 pages, 2 figure

    Ultracold atom-dimer long-range interactions beyond the 1/Rn1/R^{n} expansion

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    We investigate theoretically the combination of first-order quadrupole-quadrupole and second-order dipole-dipole effects on the long-range electrostatic interactions between a ground-state homonuclear alkali-metal dimer and an excited alkali-metal atom. As the electrostatic energy is comparable to the dimer rotational structure, we develop a general description of the long-range interactions which allows for couplings between the dimer rotational levels. The resulting adiabatic potential energy curves, which exhibit avoided crossings, cannot be expanded on the usual 1/Rn1/R^{n} series. We study in details the breakdown of this approximation in the particular case Cs2+_{2}+Cs. Our results are found promising in the prospect of accomplishing the photoassociation of ultracold trimers.Comment: Submitted to EPJD, special issue "Cold Quantum Matter - Achievements and Prospects

    Long-range interactions in the ozone molecule: spectroscopic and dynamical points of view

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    Using the multipolar expansion of the electrostatic energy, we have characterized the asymptotic interactions between an oxygen atom O(3P)(^3P) and an oxygen molecule O2(3Σg−)_2(^3\Sigma_g^-), both in their electronic ground state. We have calculated the interaction energy induced by the permanent electric quadrupoles of O and O2_2 and the van der Waals energy. On one hand we determined the 27 electronic potential energy surfaces including spin-orbit connected to the O(3P)(^3P) + O2(3Σg−)_2(^3\Sigma_g^-) dissociation limit of the O--O2_2 complex. On the other hand we computed the potential energy curves characterizing the interaction between O(3P)(^3P) and a O2(3Σg−)_2(^3\Sigma_g^-) molecule in its lowest vibrational level and in a low rotational level. Such curves are found adiabatic to a good approximation, namely they are only weakly coupled to each other. These results represent a first step for modeling the spectroscopy of ozone bound levels close to the dissociation limit, as well as the low energy collisions between O and O2_2 thus complementing the knowledge relevant for the ozone formation mechanism.Comment: Submitted to J. Chem. Phys. after revisio
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