Theory of long-range ultracold atom-molecule photoassociation

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 Cs$_2$ 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 Cs$_3$ 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

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

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 $1/R^{n}$ series. We study in details the breakdown of this approximation in the particular case Cs$_{2}+$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

Using the multipolar expansion of the electrostatic energy, we have characterized the asymptotic interactions between an oxygen atom O$(^3P)$ and an oxygen molecule O$_2(^3\Sigma_g^-)$, both in their electronic ground state. We have calculated the interaction energy induced by the permanent electric quadrupoles of O and O$_2$ and the van der Waals energy. On one hand we determined the 27 electronic potential energy surfaces including spin-orbit connected to the O$(^3P)$ + O$_2(^3\Sigma_g^-)$ dissociation limit of the O--O$_2$ complex. On the other hand we computed the potential energy curves characterizing the interaction between O$(^3P)$ and a O$_2(^3\Sigma_g^-)$ 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 O$_2$ thus complementing the knowledge relevant for the ozone formation mechanism.Comment: Submitted to J. Chem. Phys. after revisio