11 research outputs found
Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels
We have calculated the isotropic coefficients characterizing the
long-range van der Waals interaction between two identical heteronuclear
alkali-metal diatomic molecules in the same arbitrary vibrational level of
their ground electronic state . We consider the ten species made
up of Li, Na, K, Rb and Cs. Following our
previous work [M.~Lepers \textit{et.~al.}, Phys.~Rev.~A \textbf{88}, 032709
(2013)] we use the sum-over-state formula inherent to the second-order
perturbation theory, composed of the contributions from the transitions within
the ground state levels, from the transition between ground-state and excited
state levels, and from a crossed term. These calculations involve a combination
of experimental and quantum-chemical data for potential energy curves and
transition dipole moments. We also investigate the case where the two molecules
are in different vibrational levels and we show that the Moelwyn-Hughes
approximation is valid provided that it is applied for each of the three
contributions to the sum-over-state formula. Our results are particularly
relevant in the context of inelastic and reactive collisions between ultracold
bialkali molecules, in deeply bound or in Feshbach levels
Model for the hyperfine structure of electronically-excited molecules
A model for determining the hyperfine structure of the excited electronic
states of diatomic bialkali heteronuclear molecules is formulated from the
atomic hyperfine interactions, and is applied to the case of bosonic KCs
and fermionic KCs molecules. The hyperfine structure of the potential
energy curves of the states correlated to the
K(4s\,^2S_{1/2})+Cs(6p\,^2P_{1/2,3/2}) dissociation limits is described in
terms of different coupling schemes depending on the internuclear distance .
These results provide the first step in the calculation of the hyperfine
structure of rovibrational levels of these excited molecular states in the
perspective of the identification of efficient paths for creating ultracold
ground-state KCs molecules.Comment: 12 pages, 15 figure
Formation of ultracold RbCs molecules by photoassociation
The formation of ultracold metastable RbCs molecules is observed in a double
species magneto-optical trap through photoassociation below the
^85Rb(5S_1/2)+^133Cs(6P_3/2) dissociation limit followed by spontaneous
emission. The molecules are detected by resonance enhanced two-photon
ionization. Using accurate quantum chemistry calculations of the potential
energy curves and transition dipole moment, we interpret the observed
photoassociation process as occurring at short internuclear distance, in
contrast with most previous cold atom photoassociation studies. The vibrational
levels excited by photoassociation belong to the 5th 0^+ or the 4th 0^-
electronic states correlated to the Rb(5P_1/2,3/2)+Cs(6S_1/2) dissociation
limit. The computed vibrational distribution of the produced molecules shows
that they are stabilized in deeply bound vibrational states of the lowest
triplet state. We also predict that a noticeable fraction of molecules is
produced in the lowest level of the electronic ground state
Hyperfine structure of electronically-excited states of the 39 K 133 Cs molecule
International audienc
Optical Shielding of Destructive Chemical Reactions between Ultracold Ground-State NaRb Molecules
We propose a method to suppress the chemical reactions between ultracold
bosonic ground-state NaRb molecules based on optical shielding.
By applying a laser with a frequency blue-detuned from the transition between
the lowest rovibrational level of the electronic ground state , and the long-lived excited level ,
the long-range dipole-dipole interaction between the colliding molecules can be
engineered, leading to a dramatic suppression of reactive and photoinduced
inelastic collisions, for both linear and circular laser polarizations. We
demonstrate that the spontaneous emission from does
not deteriorate the shielding process. This opens the possibility for a strong
increase of the lifetime of cold molecule traps, and for an efficient
evaporative cooling. We also anticipate that the proposed mechanism is valid
for alkali-metal diatomics with sufficiently large dipole-dipole interactions
Perspectives pour la formation de molécules dipolaires froides de KCs par un processus optique
Heteronuclear alkali-metal dimers represent the class of molecules of choice for creating samples of ultracold molecules exhibiting an intrinsic large permanent electric dipole moment. Among them, the KCs molecule, with a permanent dipole moment of 1.92~Debye still remains to be observed in ultracold conditions. Based on spectroscopic studies available in the literature completed by accurate quantum chemistry calculations, we propose several optical coherent schemes to create ultracold bosonic and fermionic KCs molecules in their absolute rovibrational ground level, starting from a weakly bound level of their electronic ground state manifold. The processes rely on the existence of convenient electronically excited states allowing an efficient stimulated Raman adiabatic transfer of the level population