264 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
Study of coupled states for the (4s^{2})^{1}S + (4s4p)^{3}P asymptote of Ca_{2}
The coupled states A^{1}\Sigma_{u}^{+} (^{1}D +}1}S), c^{3}\Pi_{u} (^{3}P +
^{1}S) and a^{3}\Sigma_{u}^{+} (^{3}P +}1}S) of the calcium dimer are
investigated in a laser induced fluorescence experiment combined with
high-resolution Fourier-transform spectroscopy. A global deperturbation
analysis of the observed levels, considering a model, which is complete within
the subspace of relevant neighboring states, is performed using the Fourier
Grid Hamiltonian method. We determine the potential energy curve of the
A^{1}\Sigma_{u}^{+} and c^{3}\Pi_{u} states and the strengths of the couplings
between them. The c^{3}\Pi_{u} and \as states are of particular importance for
the description of collisional processes between calcium atoms in the ground
state ^{1}S_{0} and excited state ^{3}P_{1} applied in studies for establishing
an optical frequency standard with Ca.Comment: 15 pages, 12 figure
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
Photoassociative creation of ultracold heteronuclear 6Li40K* molecules
We investigate the formation of weakly bound, electronically excited,
heteronuclear 6Li40K* molecules by single-photon photoassociation in a
magneto-optical trap. We performed trap loss spectroscopy within a range of 325
GHz below the Li(2S_(1/2))+K(4P_(3/2)) and Li(2S_(1/2))+K(4P_(1/2)) asymptotic
states and observed more than 60 resonances, which we identify as rovibrational
levels of 7 of 8 attractive long-range molecular potentials. The long-range
dispersion coefficients and rotational constants are derived. We find large
molecule formation rates of up to ~3.5x10^7s^(-1), which are shown to be
comparable to those for homonuclear 40K_2*. Using a theoretical model we infer
decay rates to the deeply bound electronic ground-state vibrational level
X^1\Sigma^+(v'=3) of ~5x10^4s^(-1). Our results pave the way for the production
of ultracold bosonic ground-state 6Li40K molecules which exhibit a large
intrinsic permanent electric dipole moment.Comment: 6 pages, 4 figures, submitted to EP
Creating Ground State Molecules with Optical Feshbach Resonances in Tight Traps
We propose to create ultracold ground state molecules in an atomic
Bose-Einstein condensate by adiabatic crossing of an optical Feshbach
resonance. We envision a scheme where the laser intensity and possibly also
frequency are linearly ramped over the resonance. Our calculations for
Rb show that for sufficiently tight traps it is possible to avoid
spontaneous emission while retaining adiabaticity, and conversion efficiencies
of up to 50% can be expected
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
KRb Feshbach Resonances: Modeling the interatomic potential
We have observed 28 heteronuclear Feshbach resonances in 10 spin combinations
of the hyperfine ground states of a 40K 87Rb mixture. The measurements were
performed by observing the loss rates from an atomic mixture at magnetic fields
between 0 and 700 G. This data was used to significantly refine an interatomic
potential derived from molecular spectroscopy, yielding a highly consistent
model of the KRb interaction. Thus, the measured resonances can be assigned to
the corresponding molecular states. In addition, this potential allows for an
accurate calculation of the energy differences between highly excited levels
and the rovibrational ground level. This information is of particular relevance
for the formation of deeply bound heteronuclear molecules. Finally, the model
is used to predict Feshbach resonances in mixtures of 87Rb combined with 39K or
41K.Comment: 4 pages, 3 figure
Calculation of accurate permanent dipole moments of the lowest states of heteronuclear alkali dimers using extended basis sets
The obtention of ultracold samples of dipolar molecules is a current
challenge which requires an accurate knowledge of their electronic properties
to guide the ongoing experiments. In this paper, we systematically investigate
the ground state and the lowest triplet state of mixed alkali dimers (involving
Li, Na, K, Rb, Cs) using a standard quantum chemistry approach based on
pseudopotentials for atomic core representation, gaussian basis sets, and
effective terms for core polarization effects. We emphasize on the convergence
of the results for permanent dipole moments regarding the size of the gaussian
basis set, and we discuss their predicted accuracy by comparing to other
theoretical calculations or available experimental values. We also revisit the
difficulty to compare computed potential curves among published papers, due to
the differences in the modelization of core-core interaction.Comment: accepted to J. Chem. Phy
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