16 research outputs found
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
Photoionization spectroscopy of excited states of cold cesium dimers
Photoionization spectroscopy of cold cesium dimers obtained by
photoassociation of cold atoms in a magneto-optical trap is reported here. In
particular, we report on the observation and on the spectroscopic analysis of
all the excited states that have actually been used for efficient detection of
cold molecules stabilized in the triplet a^3Sigma_u^+ ground state. They are:
the (1)^3Sigma_g^+ state connected to the 6s+6p asymptote, the (2)^3Sigma_g^+
and (2)^3Pi_g states connected to the 6s+5d asymptote and finally the
(3)^3Sigma_g^+ state connected to the 6s + 7s asymptote. The detection through
these states spans a wide range of laser energies, from 8000 to 16500 cm-1,
obtained with different laser dyes and techniques. Information on the initial
distribution of cold molecules among the different vibrational levels of the
a^3Sigma_u^+ ground state is also provided. This spectroscopic knowledge is
important when conceiving schemes for quantum manipulation, population transfer
and optical detection of cold cesium molecules.Comment: 24 pages, 11 figures. Note: tables are available separately. Accepted
in Molecular Physic
Light-assisted ion-neutral reactive processes in the cold regime: radiative molecule formation vs. charge exchange
We present a combined experimental and theoretical study of cold reactive
collisions between laser-cooled Ca+ ions and Rb atoms in an ion-atom hybrid
trap. We observe rich chemical dynamics which are interpreted in terms of
non-adiabatic and radiative charge exchange as well as radiative molecule
formation using high-level electronic structure calculations. We study the role
of light-assisted processes and show that the efficiency of the dominant
chemical pathways is considerably enhanced in excited reaction channels. Our
results illustrate the importance of radiative and non-radiative processes for
the cold chemistry occurring in ion-atom hybrid traps.Comment: 5 pages, 4 figure
Systematic trends in electronic properties of alkali hydrides
Accepted for publication in Can. J. Phys. (special issue on molecular spectroscopy)Obtaining ultracold samples of dipolar molecules is a current challenge which requires an accurate knowledge of their electronic properties to guide the ongoing experiments. Alkali hydride molecules have permanent dipole significantly larger than those of mixed alkali species and, as pointed out by Taylor-Juarros et al. [Eur. Phys. J. D 31, 213 (2004)] and by Juarros et al. [Phys. Rev. A 73, 041403 (2006)], are thus good candidates for molecule formation. In this paper, using a standard quantum chemistry approach based on pseudopotentials for atomic core representation, large Gaussian basis sets, and effective core polarization potential, we systematically investigate the electronic properties of the alkali hydrides LiH to CsH, in order to discuss general trends of their behavior. We computed (for the first time for NaH, KH, RbH, and CsH) the variation of their static polarizability with the internuclear distance. Moreover, in addition to potential curves, we determine accurate values of permanent and transition dipole moments for ground and excited states depending on the internuclear distance. The behavior of electronic properties of all alkali hydrides is compared to each other, in the light of the numerous other data available in the literature. Finally, the influence of the quality of the representation of the hydrogen electronic affinity in the approach on the results is discussed