317 research outputs found
Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation of cold molecular ions
The potential energy curves, permanent and transition dipole moments, and the
static dipolar polarizability, of molecular ions composed of one alkali-metal
atom and a Strontium ion are determined with a quantum chemistry approach. The
molecular ions are treated as effective two-electron systems and are treated
using effective core potentials including core polarization, large gaussian
basis sets, and full configuration interaction. In the perspective of upcoming
experiments aiming at merging cold atom and cold ion traps, possible paths for
radiative charge exchange, photoassociation of a cold Lithium or Rubidium atom
and a Strontium ion are discussed, as well as the formation of stable molecular
ions
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
Triplet-singlet conversion in ultracold Cs and production of ground state molecules
We propose a process to convert ultracold metastable Cs molecules in
their lowest triplet state into (singlet) ground state molecules in their
lowest vibrational levels. Molecules are first pumped into an excited triplet
state, and the triplet-singlet conversion is facilitated by a two-step
spontaneous decay through the coupled
states. Using spectroscopic data and accurate quantum chemistry calculations
for Cs potential curves and transition dipole moments, we show that this
process has a high rate and competes favorably with the single-photon decay
back to the lowest triplet state. In addition, we demonstrate that this
conversion process represents a loss channel for vibrational cooling of
metastable triplet molecules, preventing an efficient optical pumping cycle
down to low vibrational levels
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
Electronic structure of the Magnesium hydride molecular ion
In this paper, using a standard quantum chemistry approach based on
pseudopotentials for atomic core representation, Gaussian basis sets, and
effective core polarization potentials, we investigate the electronic
properties of the MgH ion. We first determine potential energy curves for
several states using different basis sets and discuss their predicted accuracy
by comparing our values of the well depths and position with other available
results. We then calculate permanent and transition dipole moments for several
transitions. Finally for the first time, we calculate the static dipole
polarizability of MgH as function of the interatomic distance. This study
represents the first step towards the modeling of collisions between trapped
cold Mg ions and H molecules.Comment: submitted to J. Phys. B, special issue on Cold trapped ion
Optimal trapping wavelengths of Cs molecules in an optical lattice
The present paper aims at finding optimal parameters for trapping of Cs
molecules in optical lattices, with the perspective of creating a quantum
degenerate gas of ground-state molecules. We have calculated dynamic
polarizabilities of Cs molecules subject to an oscillating electric field,
using accurate potential curves and electronic transition dipole moments. We
show that for some particular wavelengths of the optical lattice, called "magic
wavelengths", the polarizability of the ground-state molecules is equal to the
one of a Feshbach molecule. As the creation of the sample of ground-state
molecules relies on an adiabatic population transfer from weakly-bound
molecules created on a Feshbach resonance, such a coincidence ensures that both
the initial and final states are favorably trapped by the lattice light,
allowing optimized transfer in agreement with the experimental observation
Giant enhancement of photodissociation of polar dimers in electric fields
We explore the photodissociation of polar dimers in static electric fields in
the cold regime using the example of the LiCs molecule. A giant enhancement of
the differential cross section is found for laboratory electric field
strengths, and analyzed with varying rovibrational bound states, continuum
energies as well as field strengths.Comment: 6 pages, 6 figure
Resonant Coupling in the Heteronuclear Alkali Dimers for Direct Photoassociative Formation of X(0,0) Ultracold Molecules
Promising pathways for photoassociative formation of ultracold heteronuclear
alkali metal dimers in their lowest rovibronic levels (denoted X(0,0)) are
examined using high quality ab initio calculations of potential energy curves
currently available. A promising pathway for KRb, involving the resonant
coupling of the and states just below the lowest excited
asymptote (K()+Rb()), is found to occur also for RbCs and less
promisingly for KCs as well. The resonant coupling of the and
states, also just below the lowest excited asymptote, is found to be
promising for LiNa, LiK, LiRb, and less promising for LiCs and KCs. Direct
photoassociation to the state near dissociation appears promising in
the final dimers, NaK, NaRb, and NaCs, although detuning more than 100
cm below the lowest excited asymptote may be required.Comment: 20 pages, 12 figures, Submitted to Journal of Physical Chemistry
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