163 research outputs found
Photoassociative Production and Trapping of Ultracold KRb Molecules
We have produced ultracold heteronuclear KRb molecules by the process of
photoassociation in a two-species magneto-optical trap. Following decay of the
photoassociated KRb*, the molecules are detected using two-photon ionization
and time-of-flight mass spectroscopy of KRb. A portion of the metastable
triplet molecules thus formed are magnetically trapped. Photoassociative
spectra down to 91 cm below the K(4) + Rb (5) asymptote have
been obtained. We have made assignments to all eight of the attractive Hund's
case (c) KRb* potential curves in this spectral region.Comment: 4 pages, 4 figure
Macrodimers: ultralong range Rydberg molecules
We study long range interactions between two Rydberg atoms and predict the
existence of ultralong range Rydberg dimers with equilibrium distances of many
thousand Bohr radii. We calculate the dispersion coefficients ,
and for two rubidium atoms in the same excited level , and find
that they scale like , and , respectively. We show that
for certain molecular symmetries, these coefficients lead to long range
potential wells that can support molecular bound levels. Such macrodimers would
be very sensitive to their environment, and could probe weak interactions. We
suggest experiments to detect these macrodimers.Comment: 4 pages, submitted to PR
Enhancement of the formation of ultracold Rb molecules due to resonant coupling
We have studied the effect of resonant electronic state coupling on the
formation of ultracold ground-state Rb. Ultracold Rb molecules
are formed by photoassociation (PA) to a coupled pair of states,
and , in the region below the
limit. Subsequent radiative decay produces high vibrational levels of the
ground state, . The population distribution of these state
vibrational levels is monitored by resonance-enhanced two-photon ionization
through the state. We find that the populations of vibrational
levels =112116 are far larger than can be accounted for by the
Franck-Condon factors for transitions with
the state treated as a single channel. Further, the
ground-state molecule population exhibits oscillatory behavior as the PA laser
is tuned through a succession of state vibrational levels. Both of
these effects are explained by a new calculation of transition amplitudes that
includes the resonant character of the spin-orbit coupling of the two
states. The resulting enhancement of more deeply bound ground-state molecule
formation will be useful for future experiments on ultracold molecules.Comment: 6 pages, 5 figures; corrected author lis
Scattering length of the ground state Mg+Mg collision
We have constructed the X 1SIGMAg+ potential for the collision between two
ground state Mg atoms and analyzed the effect of uncertainties in the shape of
the potential on scattering properties at ultra-cold temperatures. This
potential reproduces the experimental term values to 0.2 inverse cm and has a
scattering length of +1.4(5) nm where the error is prodominantly due to the
uncertainty in the dissociation energy and the C6 dispersion coefficient. A
positive sign of the scattering length suggests that a Bose-Einstein condensate
of ground state Mg atoms is stable.Comment: 15 pages, 3 figures, Submitted Phys. Rev.
Photoassociation spectroscopy of cold He(2(3)S) atoms
We observe vibrational states by photoassociation spectroscopy of cold He(2 3S) atoms. Photoassociation resonances are detected as peaks in the Penning ionization rate over a frequency range of 20 GHz below the atomic 2 3S1-2 3P2 transition frequency. We have observed three vibrational series, of which two can be identified. A possible mechanism to explain the observed increase of the Penning ionization rate is discussed
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