324 research outputs found
Anisotropy induced Feshbach resonances in a quantum dipolar gas of magnetic atoms
We explore the anisotropic nature of Feshbach resonances in the collision
between ultracold magnetic submerged-shell dysprosium atoms, which can only
occur due to couplings to rotating bound states. This is in contrast to
well-studied alkali-metal atom collisions, where most Feshbach resonances are
hyperfine induced and due to rotation-less bound states. Our novel
first-principle coupled-channel calculation of the collisions between
open-4f-shell spin-polarized bosonic dysprosium reveals a striking correlation
between the anisotropy due to magnetic dipole-dipole and electrostatic
interactions and the Feshbach spectrum as a function of an external magnetic
field. Over a 20 mT magnetic field range we predict about a dozen Feshbach
resonances and show that the resonance locations are exquisitely sensitive to
the dysprosium isotope.Comment: 5 pages, 4 figure
Electronic structure and spectroscopy of O2 and O2+
We carried out a comprehensive SCF MRD--CI ab initio study of the
electronic
structure of O and O. Potential energy curves (PECs) of
about 150
electronic states of O and
about
100 of O, as well as a number of
states of
O were computed. The cc--pVQZ basis set augmented with diffuse
functions was employed. Spectroscopic parameters
( , ,
IP, etc.) are reported.
A preliminary sample of the results will be presented. The electronic absorption
spectrum of O has proved difficult to analyze/interpret
due to the unusually large number of electronic states which arise
from
the peculiar open--shell structure of both the oxygen atomic fragments and the
O molecule. For instance, there are 62 valence molecular electronic
states which
correlate to the six lowest dissociation limits resulting from
the three valence O atom fragment states (P, D, S).
In addition, there are several Rydberg series
converging to the X ground ionic state and to the lowest
two excited states of the cation, a and A.
Furthermore, a number of interactions of various types among several electronic states result in rovibronic perturbations
which manifest themselves, e.g., as irregular vibronic structure,
hence severely complicating the
assignment of the absorption features and the analysis and
interpretation of the spectrum.
An overview of the electronic states and spectroscopy of O will be presented.
A chief motivation of this study of O was
to try to provide a theoretical insight on the nature,
energetic position, shape, and dissociation asymptotes,
of electronic states located in the 4 eV energy region
encompassed between the O ground state X (IP eV)
and the first excited state of the cation a
(IP eV).
This in order to aid in the interpretation of experimental data
related to the mechanism(s) of the neutral dissociation of the O
(Rydberg) superexcited states,
which competes with autoionization.
We are currently striving to compute PECs of relatively highly
excited states of O located in the 12--16 eV energy region which might
help to visualize possible pathways for the
neutral XUV photodissociation of the I, I and I
superexcited states of O leading to the O(P) + O(S, S) dissociation limits.Ope
Zero kinetic energy-pulsed field ionization and resonance enhanced multiphoton ionization photoelectron spectroscopy: Ionization dynamics of Rydberg states in HBr
The results of rotationally resolved resonance enhanced multiphoton ionization photoelectron spectroscopy and zero kinetic energy‐pulsed field ionization studies on HBr via various rotational levels of the F^ 1Δ_2 and f^ 3Δ_2 Rydberg states are reported. These studies lead to an accurate determination of the lowest ionization threshold as 94 098.9±1 cm^(−1). Observed rotational and spin–orbit branching ratios are compared to the results of ab initio calculations. The differences between theory and experiment highlight the dominant role of rotational and spin–orbit interactions for the dynamic properties of the high‐n Rydberg states involved in the pulsed field ionization process
Marked influence of the nature of chemical bond on CP-violating signature in molecular ions and
Heavy polar molecules offer a great sensitivity to the electron Electric
Dipole Moment(EDM). To guide emerging searches for EDMs with molecular ions, we
estimate the EDM-induced energy corrections for hydrogen halide ions
and in their respective ground states. We find that the energy corrections due to EDM for the two
ions differ by an unexpectedly large factor of fifteen. We demonstrate that a
major part of this enhancement is due to a dissimilarity in the nature of the
chemical bond for the two ions: the bond that is nearly of ionic character in
exhibits predominantly covalent nature in .
We conclude that because of this enhancement the HI ion may be a
potentially competitive candidate for the EDM search.Comment: This manuscript has been accepted for publication in Physical Review
Letters. The paper is now being prepared for publicatio
Laser-induced fluorescence studies of HfF+ produced by autoionization
Autoionization of Rydberg states of HfF, prepared using the optical-optical
double resonance (OODR) technique, holds promise to create HfF+ in a particular
Zeeman level of a rovibronic state for an electron electric dipole moment
(eEDM) search. We characterize a vibronic band of Rydberg HfF at 54 cm-1 above
the lowest ionization threshold and directly probe the state of the ions formed
from this vibronic band by performing laser-induced fluorescence (LIF) on the
ions. The Rydberg HfF molecules show a propensity to decay into only a few ion
rotational states of a given parity and are found to preserve their orientation
qualitatively upon autoionization. We show empirically that we can create 30%
of the total ion yield in a particular |J+,M+> state and present a simplified
model describing autoionization from a given Rydberg state that assumes no
angular dynamics.Comment: 8 pages, 5 figure
Relations between Rydberg-valence interactions in the O₂ molecule
Using a single-configuration formulation, analytical expressions are derived for the (X²Πg) nsσg, npπu, and npσu Rydberg-valence interaction matrix elements in O₂. In addition, new results from diabatic, coupled-channel deperturbations of experimental data dependent on these interactions are reported for n=3 and 4. Using these results, the large differences in magnitude between the Rydberg-valence couplings for the constituent states of the npπuRydberg complex that are predicted by the analytical expressions are verified experimentally. Effective values for several two-electron integrals are obtained semiempirically through comparison between analytical expressions and deperturbed experimental values for the Rydberg-state energies and Rydberg-valence couplings, allowing predictions to be made for the spectroscopy of the npπu ¹Σ−uRydberg states which have yet to be observed
Hyperfine, rotational and Zeeman structure of the lowest vibrational levels of the Rb \tripletex state
We present the results of an experimental and theoretical study of the
electronically excited \tripletex state of Rb molecules. The
vibrational energies are measured for deeply bound states from the bottom up to
using laser spectroscopy of ultracold Rb Feshbach molecules. The
spectrum of each vibrational state is dominated by a 47\,GHz splitting into a
\cog and \clg component caused mainly by a strong second order spin-orbit
interaction. Our spectroscopy fully resolves the rotational, hyperfine, and
Zeeman structure of the spectrum. We are able to describe to first order this
structure using a simplified effective Hamiltonian.Comment: 10 pages, 7 figures, 2 table
Observation of Feshbach resonances in an ultracold gas of Cr
We have observed Feshbach resonances in elastic collisions between ultracold
Cr atoms. This is the first observation of collisional Feshbach
resonances in an atomic species with more than one valence electron. The zero
nuclear spin of Cr and thus the absence of a Fermi-contact interaction
leads to regularly-spaced resonance sequences. By comparing resonance positions
with multi-channel scattering calculations we determine the s-wave scattering
length of the lowest potentials to be
\unit[112(14)]{a_0}, \unit[58(6)]{a_0} and -\unit[7(20)]{a_0} for S=6, 4,
and 2, respectively, where a_{0}=\unit[0.0529]{nm}.Comment: 4 pages, 2 figures, 1 tabl
Validity of adiabaticity in Cavity QED
This paper deals with the concept of adiabaticity for fully quantum
mechanically cavity QED models. The physically interesting cases of Gaussian
and standing wave shapes of the cavity mode are considered. An analytical
approximate measure for adiabaticity is given and compared with numerical wave
packet simulations. Good agreement is obtained where the approximations are
expected to be valid. Usually for cavity QED systems, the large atom-field
detuning case is considered as the adiabatic limit. We, however, show that
adiabaticity is also valid, for the Gaussian mode shape, in the opposite limit.
Effective semiclassical time dependent models, which do not take into account
the shape of the wave packet, are derived. Corrections to such an effective
theory, which are purely quantum mechanical, are discussed. It is shown that
many of the results presented can be applied to time dependent two-level
systems.Comment: 10 pages, 9 figure
- …