1,549 research outputs found
Observation of near-quantum-limited velocity distributions of a levitated particle
We demonstrate time-of-flight measurements for an ultracold levitated
nanoparticle and reveal its translational velocity in the quantum regime. We
discover that the velocity distributions obtained with repeated measurements
are significantly broadened via librational motions of the nanoparticle. Under
feedback cooling on all the librational motions, we recover the velocity
distributions in reasonable agreement with an expectation from the occupation
number, with approximately twice the width of the quantum limit. The strong
impact of librational motions on the translational motions is understood as a
result of the deviation between the libration center and the center of mass,
induced by the asymmetry of the nanoparticle. Our results elucidate the
importance of the control over librational motions and establish the basis for
exploring quantum mechanical properties of levitated nanoparticles in terms of
their velocity.Comment: 7 pages, 7 file
Direct evaporative cooling of 41K into a Bose-Einstein condensate
We have investigated the collisional properties of 41K atoms at ultracold
temperature. To show the possibility to use 41K as a coolant, a Bose-Einstein
condensate of 41K atoms in the stretched state (F=2, m_F=2) was created for the
first time by direct evaporation in a magnetic trap. An upper bound of three
body loss coefficient for atoms in the condensate was determined to be 4(2)
10^{-29} cm -6 s-1. A Feshbach resonance in the F=1, m_F=-1 state was observed
at 51.42(5) G, which is in good agreement with theoretical prediction.Comment: 4 pages, 4 figure
Coherent transfer of photoassociated molecules into the rovibrational ground state
We report on the direct conversion of laser-cooled 41K and 87Rb atoms into
ultracold 41K87Rb molecules in the rovibrational ground state via
photoassociation followed by stimulated Raman adiabatic passage.
High-resolution spectroscopy based on the coherent transfer revealed the
hyperfine structure of weakly bound molecules in an unexplored region. Our
results show that a rovibrationally pure sample of ultracold ground-state
molecules is achieved via the all-optical association of laser-cooled atoms,
opening possibilities to coherently manipulate a wide variety of molecules.Comment: 4 pages, 4 figure
Predicting and verifying transition strengths from weakly bound molecules
We investigated transition strengths from ultracold weakly bound 41K87Rb
molecules produced via the photoassociation of laser-cooled atoms. An accurate
potential energy curve of the excited state (3)1Sigma+ was constructed by
carrying out direct potential fit analysis of rotational spectra obtained via
depletion spectroscopy. Vibrational energies and rotational constants extracted
from the depletion spectra of v'=41-50 levels were combined with the results of
the previous spectroscopic study, and they were used for modifying an ab initio
potential. An accuracy of 0.14% in vibrational level spacing and 0.3% in
rotational constants was sufficient to predict the large observed variation in
transition strengths among the vibrational levels. Our results show that
transition strengths from weakly bound molecules are a good measure of the
accuracy of an excited state potential.Comment: 7 pages, 7 figure
Bose-Einstein Condensation of Erbium
We report on the achievement of Bose-Einstein condensation of erbium atoms
and on the observation of magnetic Feshbach resonances at low magnetic field.
By means of evaporative cooling in an optical dipole trap, we produce pure
condensates of Er, containing up to atoms. Feshbach
spectroscopy reveals an extraordinary rich loss spectrum with six loss
resonances already in a narrow magnetic-field range up to 3 G. Finally, we
demonstrate the application of a low-field Feshbach resonance to produce a
tunable dipolar Bose-Einstein condensate and we observe its characteristic
d-wave collapse.Comment: 4 pages, 3 figure
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