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Register a new userLong-range additive and nonadditive potentials in a hybrid system: Ground state atom, excited state atom, and ion
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We report a theoretical study on the long-range additive and nonadditive potentials for a three-body hybrid atom-atom-ion system composed of one ground $S$ state Li atom, one excited $P$ state Li atom and one ground $S$ state Li$^+$ ion, Li($2,^{2}S$)-Li($2,^{2}P$)-Li$^+(1,^{1}S$). The interaction coefficients are evaluated with highly accurate wave functions calculated variationally in Hylleraas coordinates. For this hybrid system the three-body nonadditive collective interactions (appearing in second-order) induced by the energy degeneracy and enhanced by the induction effect of the Li$^+$ ion through the internal electric field can be strong and even stronger than the two-body additive interactions at the same order. We find that for particular geometries the two-body additive interactions of the system sum to zero leaving only three-body nonadditive collective interactions making the present system potentially a platform to explore quantum three-body collective effects. We also extract first-principles leading coefficients of the long-range electrostatic, induction, and dispersion energies of Li$^+_2$ electronic states correlating to Li($2,^{2}P$)-Li$^+(1,^{1}S$), which until now were not available in the literature. The results should be especially valuable for the exploration of schemes to create trimers with ultracold atoms and ions in optical lattices.
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We propose a novel type of Rydberg dimer, consisting of a Rydberg-state atom bound to a distant positive ion. The molecule is formed through long-range electric-multipole interaction between the Rydberg atom and the point-like ion. We present potential energy curves (PECs) that are asymptotically connected with Rydberg $nP$- or $nD$-states of rubidium or cesium. The PECs exhibit deep, long-range wells which support many vibrational states of Rydberg-atom-ion molecules (RAIMs). We consider photo-association of RAIMs in both the weak and the strong optical-coupling regimes between initial and Rydberg states of the neutral atom. Experimental considerations for the realization of RAIMs are discussed.
Since their first experimental observation, ultralong-range Rydberg molecules consisting of a highly excited Rydberg atom and a ground state atom have attracted the interest in the field of ultracold chemistry. Especially the intriguing properties like size, polarizability and type of binding they inherit from the Rydberg atom are of interest. An open question in the field is the reduced lifetime of the molecules compared to the corresponding atomic Rydberg states. In this letter we present an experimental study on the lifetimes of the ^3Sigma (5s-35s) molecule in its vibrational ground state and in an excited state. We show that the lifetimes depends on the density of ground state atoms and that this can be described in the frame of a classical scattering between the molecules and ground state atoms. We also find that the excited molecular state has an even more reduced lifetime compared to the ground state which can be attributed to an inward penetration of the bound atomic pair due to imperfect quantum reflection that takes place in the special shape of the molecular potential.
We report the realization of a heteronuclear two-atom of $^{87}$Rb-$^{85}$Rb in the ground state of an optical tweezer (OT). Starting by trapping two different isotopic single atoms, a $^{87}$Rb and a $^{85}$Rb in two strongly focused and linearly polarized OT with 4 $mu$m apart, we perform simultaneously three dimensional Raman sideband cooling for both atoms and the obtained 3D ground state probabilities of $^{87}$Rb and $^{85}$Rb are 0.91(5) and 0.91(10) respectively. There is no obvious crosstalk observed during the cooling process. We then merge them into one tweezer via a species-dependent transport, where the species-dependent potentials are made by changing the polarization of the OTs for each species from linear polarization to the desired circular polarization. The measurable increment of vibrational quantum due to merging is $0.013(1)$ for the axial dimension. This two-atom system can be used to investigate cold collisional physics, to form quantum logic gates, and to build a single heteronuclear molecule. It can also be scaled up to few-atom regime and extended to other atomic species and molecules, and thus to ultracold chemistry.
I revisit the problem of the interaction between two dissimilar atoms with one atom in an excited state, recently addressed by the authors of Refs.[1-3], and for which precedent approaches have given conflicting results. In the first place, I discuss to what extent Refs.[1], [2] and [3] provide equivalent results. I show that the phase-shift rate of the two-atom wave function computed in Ref.[1], the van der Waals potential of the excited atom in Ref.[2] and the level shift of the excited atom in Ref.[3] possess equivalent expressions in the quasistationary approximation. In addition, I show that the level shift of the ground state atom computed in Ref.[3] is equivalent to its van der Waals potential. A diagrammatic representation of all those quantities is provided. The equivalences among them are however not generic. In particular, it is found that for the case of the interaction between two identical atoms excited, the phase-shift rate and the van der Waals potentials differ. Concerning the conflicting results of previous approaches in regards to the spatial oscillation of the interactions, I conclude in agreement with Refs.[1,3] that they refer to different physical quantities. The impacts of free-space dissipation and finite excitation rates on the dynamics of the potentials are analyzed. In contrast to Ref.[3], the oscillatory versus monotonic spatial forms of the potentials of each atom are found not to be related to the reversible versus irreversible nature of the excitation transfer involved.
It is established within the Thomas -- Fermi model that a bound state of a proton with a heavy atom should exist. On the one hand, the electrons of the atom screen the protons field. This decreases the repulsion force between the proton and the nucleus. On the other hand, the attraction force between the proton and the electrons is directed towards the gradient of the electron density, i. e. towards the nucleus. For instance, for Z=80 both forces become equal at approximately 0.6a where a is the Bohr radius. The corresponding minimum of the proton potential energy is in the region of negative energies (attraction) that can be of the order of several tens of eV. We propose to call such a system a binuclear atom. In contrast to the molecules where a coupling with a hydrogen atom is due to an essential modification of one or several states of the outer electrons the formation of a binuclear atom is a result of collective response of the whole system of inner electrons to the screened potential of a proton that is well inside the electron system of the heavy atom. The variation of the wave function of each electron can be considered as a small perturbation. The bound state is formed as a result of joint action of a large number of perturbed inner electrons. The important problem concerning the accuracy of our calculation within the Thomas -- Fermi model is discussed.
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