16 research outputs found
Observation of Interactions between Trapped Ions and Ultracold Rydberg Atoms
We report on the observation of interactions between ultracold Rydberg atoms
and ions in a Paul trap. The rate of observed inelastic collisions, which
manifest themselves as charge transfer between the Rydberg atoms and ions,
exceeds that of Langevin collisions for ground state atoms by about three
orders of magnitude. This indicates a huge increase in interaction strength. We
study the effect of the vacant Paul trap's electric fields on the Rydberg
excitation spectra. To quantitatively describe the exhibited shape of the ion
loss spectra, we need to include the ion-induced Stark shift on the Rydberg
atoms. Furthermore, we demonstrate Rydberg excitation on a dipole-forbidden
transition with the aid of the electric field of a single trapped ion. Our
results confirm that interactions between ultracold atoms and trapped ions can
be controlled by laser coupling to Rydberg states. Adding dynamic Rydberg
dressing may allow for the creation of spin-spin interactions between atoms and
ions, and the elimination of collisional heating due to ionic micromotion in
atom-ion mixtures.Comment: 7 pages, 5 figures, including appendices. Note that the title has
been changed in version
Rydberg atom-ion collisions in cold environments
Low-energy collisions of Rydberg atom-ion systems are investigated theoretically. We present the parameter space associated with suitable approaches for the dynamics of Rydberg atom-ion collisions, i.e., quantum, Langevin, and classical exchange regimes, showing that for the lowest reachable temperatures a classical treatment is appropriate. A quasiclassical trajectory method is used to study charge exchange cross sections for Li∗−Li+ and Li∗−Cs+ at collision energies down to 1K. For cold collisions we find the charge exchange cross section deviating from the n4 geometric scaling. Furthermore, for low-energy collisions, we find both an influence of the ionic core repulsion as well as variations for two different models used for describing the electron-core potential
Trap-assisted complexes in cold atom-ion collisions
We theoretically investigate the trap-assisted formation of complexes in
atom-ion collisions and their impact on the stability of the trapped ion. The
time-dependent potential of the Paul trap facilitates the formation of
temporary complexes by reducing the energy of the atom, which gets temporarily
stuck in the atom-ion potential. As a result, those complexes significantly
impact termolecular reactions leading to molecular ion formation via three-body
recombination. We find that complex formation is more pronounced in systems
with heavy atoms, but the mass has no influence on the lifetime of the
transient state. Instead, the complex formation rate strongly depends on the
amplitude of the ion's micromotion. We also show that complex formation
persists even in the case of a time-independent harmonic trap. In this case, we
find higher formation rates and longer lifetimes than the Paul trap, indicating
that the atom-ion complex plays an essential role in atom-ion mixtures in
optical traps.Comment: 6 pages, 4 figure
Observation of Chemical Reactions between a Trapped Ion and Ultracold Feshbach Dimers
We measure chemical reactions between a single trapped 174Yb+ ion and ultracold Li2 dimers. This produces LiYb+molecular ions that we detect via mass spectrometry. We explain the reaction rates by modeling the dimer density as a function of the magnetic field and obtain excellent agreement when we assume the reaction to follow the Langevin rate. Our results present a novel approach towards the creation of cold molecular ions and point to the exploration of ultracold chemistry in ion molecule collisions. What is more, with a detection sensitivity below molecule densities of 1014  m-3we provide a new method to detect low-density molecular gases
Buffer gas cooling of a trapped ion to the quantum regime
Great advances in precision quantum measurement have been achieved with
trapped ions and atomic gases at the lowest possible temperatures. These
successes have inspired ideas to merge the two systems. In this way one can
study the unique properties of ionic impurities inside a quantum fluid or
explore buffer gas cooling of the trapped ion quantum computer. Remarkably, in
spite of its importance, experiments with atom-ion mixtures remained firmly
confined to the classical collision regime. We report a collision energy of
1.15(0.23) times the -wave energy (or 9.9(2.0)~K) for a trapped
ytterbium ion in an ultracold lithium gas. We observed a deviation from
classical Langevin theory by studying the spin-exchange dynamics, indicating
quantum behavior in the atom-ion collisions. Our results open up numerous
opportunities, such as the exploration of atom-ion Feshbach resonances, in
analogy to neutral systems.Comment: 8 pages, 6 figures including appendice