42 research outputs found
Mass scaling and non-adiabatic effects in photoassociation spectroscopy of ultracold strontium atoms
We report photoassociation spectroscopy of ultracold Sr atoms near the
intercombination line and provide theoretical models to describe the obtained
bound state energies. We show that using only the molecular states correlating
with the asymptote is insufficient to provide a mass scaled
theoretical model that would reproduce the bound state energies for all
isotopes investigated to date: Sr, Sr and Sr. We attribute
that to the recently discovered avoided crossing between the
() and () potential
curves at short range and we build a mass scaled interaction model that
quantitatively reproduces the available and bound state energies
for the three stable bosonic isotopes. We also provide isotope-specific
two-channel models that incorporate the rotational (Coriolis) mixing between
the and curves which, while not mass scaled, are capable of
quantitatively describing the vibrational splittings observed in experiment. We
find that the use of state-of-the-art ab initio potential curves significantly
improves the quantitative description of the Coriolis mixing between the two -8
GHz bound states in Sr over the previously used model potentials. We
show that one of the recently reported energy levels in Sr does not
follow the long range bound state series and theorize on the possible causes.
Finally, we give the Coriolis mixing angles and linear Zeeman coefficients for
all of the photoassociation lines. The long range van der Waals coefficients
~a.u. and ~a.u. are reported.Comment: 14 pages, 7 tables, 5 figures. Submitted to Phys. Rev.
Controlled Production of Sub-Radiant States of a Diatomic Molecule in an Optical Lattice
We report successful production of sub-radiant states of a two-atom system in
a three-dimensional optical lattice starting from doubly occupied sites in a
Mott insulator phase of a quantum gas of atomic ytterbium. We can selectively
produce either sub-radiant 1g state or super-radiant 0u state by choosing the
excitation laser frequency. The inherent weak excitation rate for the
sub-radiant 1g state is overcome by the increased atomic density due to the
tight-confinement in a three-dimensional optical lattice. Our experimental
measurements of binding energies, linewidth, and Zeeman shift confirm
observation of sub-radiant levels of the 1g state of the Yb_2 molecule.Comment: To be published in Phys. Rev. Let
Line-shape study of CO perturbed by N with mid-infrared frequency comb-based Fourier-transform spectroscopy
We developed a mid-infrared optical frequency comb-based Fourier-transform
spectrometer and performed a line-shape study of the fundamental vibrational
band of CO perturbed by N, which is crucial for atmospheric science and
astronomical observations. The comb-based FTS enabled us to measure the whole
vibrational band with high resolution and precision at several pressures
between 10 and 400 Torr. Observed absorption profiles were fitted with the
speed-dependent Voigt profile. Collisional broadening, speed-dependent
collisional width and shift coefficients are derived. The reliability of our
results is established from considerations of systematic errors and comparison
with previous studies.Comment: 14 pages, 8 figure
Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths
By performing high-resolution two-color photoassociation spectroscopy, we
have successfully determined the binding energies of several of the last bound
states of the homonuclear dimers of six different isotopes of ytterbium. These
spectroscopic data are in excellent agreement with theoretical calculations
based on a simple model potential, which very precisely predicts the s-wave
scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave
scattering lengths for collision of two atoms of the same isotopic species are
13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb,
-31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb,
and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the
long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic
units J nm^6).Comment: 9 pages, 7 figure
Buffer gas induced collision shift for the Sr clock transition
Precision saturation spectroscopy of the is
performed in a vapor cell filled with various rare gas including He, Ne, Ar,
and Xe. By continuously calibrating the absolute frequency of the probe laser,
buffer gas induced collision shifts of kHz are detected with gas
pressure of 1-20 mTorr. Helium gave the largest fractional shift of . Comparing with a simple impact calculation and a
Doppler-limited experiment of Holtgrave and Wolf [Phys. Rev. A {\bf 72}, 012711
(2005)], our results show larger broadening and smaller shifting coefficient,
indicating effective atomic loss due to velocity changing collisions. The
applicability of the result to the optical lattice clock
transition is also discussed
Weakly bound molecules as sensors of new gravitylike forces
Several extensions to the Standard Model of particle physics, including light dark matter candidates and unification theories predict deviations from Newtonâs law of gravitation. For macroscopic distances, the inverse-square law of gravitation is well confirmed by astrophysical observations and laboratory experiments. At micrometer and shorter length scales, however, even the state-of-the-art constraints on deviations from gravitational interaction, whether provided by neutron scattering or precise measurements of forces between macroscopic bodies, are currently many orders of magnitude larger than gravity itself. Here we show that precision spectroscopy of weakly bound molecules can be used to constrain non-Newtonian interactions between atoms. A proof-of-principle demonstration using recent data from photoassociation spectroscopy of weakly bound Yb2 molecules yields constraints on these new interactions that are already close to state-of-the-art neutron scattering experiments. At the same time, with the development of the recently proposed optical molecular clocks, the neutron scattering constraints could be surpassed by at least two orders of magnitude
Measurement and calculation of CO (7-0) overtone line intensities
Intensities of 14 lines in the sixth overtone (7-0) band of carbon monoxide (12C16O) are measured in the visible range between 14 300 and 14 500 cm-1 using a frequency-stabilized cavity ring-down spectrometer. This is the first observation of such a high and weak overtone spectrum of the CO molecule. A theoretical model is constructed and tested based on the use of a high accuracy ab initio dipole moment curve and a semi-empirical potential energy curve. Accurate studies of high overtone transitions provide a challenge to both experiment and theory as the lines are very weak: below 2 à 10-29 cm molecule-1 at 296 K. Agreement between theory and experiment within the experimental uncertainty of a few percent is obtained. However, this agreement is only achieved after issues with the stability of the Davidson correction to the multi-reference configuration interaction calculations are addressed
Absolute measurement of the ^{1}S_{0}âââ^{3}P_{0} clock transition in neutral ^{88}Sr over the 330 km-long stabilized fibre optic link
We report a stability below of two independent optical
lattice clocks operating with bosonic Sr isotope. The value
(429228066418008.3(1.9)(0.9)~Hz) of the absolute
frequency of the - transition was measured with an
optical frequency comb referenced to the local representation of the UTC by the
330 km-long stabilized fibre optical link. The result was verified by series of
measurements on two independent optical lattice clocks and agrees with
recommendation of Bureau International des Poids et Mesures