3,931 research outputs found
Ultracold Dipolar Gas of Fermionic NaK Molecules in their Absolute Ground State
We report on the creation of an ultracold dipolar gas of fermionic
NaK molecules in their absolute rovibrational and hyperfine
ground state. Starting from weakly bound Feshbach molecules, we demonstrate
hyperfine resolved two-photon transfer into the singlet ground state, coherently bridging a binding energy
difference of 0.65 eV via stimulated rapid adiabatic passage. The
spin-polarized, nearly quantum degenerate molecular gas displays a lifetime
longer than 2.5 s, highlighting NaK's stability against two-body chemical
reactions. A homogeneous electric field is applied to induce a dipole moment of
up to 0.8 Debye. With these advances, the exploration of many-body physics with
strongly dipolar Fermi gases of NaK molecules is in experimental
reach.Comment: 5 pages, 5 figure
Two-Photon Pathway to Ultracold Ground State Molecules of NaK
We report on high-resolution spectroscopy of ultracold fermionic
\nak~Feshbach molecules, and identify a two-photon pathway to the rovibrational
singlet ground state via a resonantly mixed \Bcres intermediate state.
Photoassociation in a Na-K atomic mixture and one-photon
spectroscopy on \nak~Feshbach molecules reveal about 20 vibrational levels of
the electronically excited \ctrip state. Two of these levels are found to be
strongly perturbed by nearby \Bsing states via spin-orbit coupling, resulting
in additional lines of dominant singlet character in the perturbed complex
{}, or of
resonantly mixed character in {}. The dominantly singlet level is used to locate
the absolute rovibrational singlet ground state via Autler-Townes spectroscopy. We demonstrate coherent
two-photon coupling via dark state spectroscopy between the predominantly
triplet Feshbach molecular state and the singlet ground state. Its binding
energy is measured to be 5212.0447(1) \cm, a thousand-fold improvement in
accuracy compared to previous determinations. In their absolute singlet ground
state, \nak~molecules are chemically stable under binary collisions and possess
a large electric dipole moment of Debye. Our work thus paves the way
towards the creation of strongly dipolar Fermi gases of NaK molecules.Comment: 23 pages, 8 figure
Regulation of Leukocyte-Derived Matrix Metalloproteinases and Azurophilic Enzymes in Human Diabetic Ketoacidosis
Diabetic Ketoacidosis (DKA) is associated with pediatric cerebrovascular-related complications. DKA-associated inflammation instigates leukocyte adherence to the brain microvascular endothelium. As adhered leukocytes release enzymes that compromise vascular integrity, we questioned a role for leukocyte-derived matrix metalloproteinases (MMPs) and azurophilic enzymes (elastase, proteinase-3, myeloperoxidase). Our aims were to measure leukocyte-derived enzymes in DKA plasma, determine associations with DKA severity and investigate their effect on the cerebrovascular endothelium.
Plasma was obtained from children with type-1 diabetes, either in acute DKA or insulin-controlled. DKA was associated with altered plasma levels of ↓MMP-2, ↑MMP-8, ↑MMP-9 and ↑TIMP-4, which are largely leukocyte in origin. DKA was also associated with elevated plasma leukocyte elastase, proteinase-3 and myeloperoxidase. MMP-8, MMP-9 and proteinase-3 were positively correlated with DKA severity. Azurophilic enzymes decreased ZO-1 and degraded β-catenin in cerebrovascular endothelium.
In summary, DKA is associated with dynamic regulation of leukocyte proteolytic enzymes that can impair blood brain barrier integrity
Coherent Microwave Control of Ultracold NaK Molecules
We demonstrate coherent microwave control of rotational and hyperfine states
of trapped, ultracold, and chemically stable NaK molecules.
Starting with all molecules in the absolute rovibrational and hyperfine ground
state, we study rotational transitions in combined magnetic and electric fields
and explain the rich hyperfine structure. Following the transfer of the entire
molecular ensemble into a single hyperfine level of the first rotationally
excited state, , we observe collisional lifetimes of more than , comparable to those in the rovibrational ground state, . Long-lived
ensembles and full quantum state control are prerequisites for the use of
ultracold molecules in quantum simulation, precision measurements and quantum
information processing.Comment: 5 pages, 4 figure
Ultracold Fermionic Feshbach Molecules of NaK
We report on the formation of ultracold fermionic Feshbach molecules of
NaK, the first fermionic molecule that is chemically stable in
its ground state. The lifetime of the nearly degenerate molecular gas exceeds
100 ms in the vicinity of the Feshbach resonance. The measured dependence of
the molecular binding energy on the magnetic field demonstrates the
open-channel character of the molecules over a wide field range and implies
significant singlet admixture. This will enable efficient transfer into the
singlet vibrational ground state, resulting in a stable molecular Fermi gas
with strong dipolar interactions.Comment: 5 pages, 4 figure
Correlated photon-pair generation in reverse-proton-exchange PPLN waveguides with integrated mode demultiplexer at 10 GHz clock
We report 10-ps correlated photon pair generation in periodically-poled
reverse-proton-exchange lithium niobate waveguides with integrated mode
demultiplexer at a wavelength of 1.5-um and a clock of 10 GHz. Using
superconducting single photon detectors, we observed a coincidence to
accidental count ratio (CAR) as high as 4000. The developed photon-pair source
may find broad application in quantum information systems as well as quantum
entanglement experiments.Comment: 6 pages, 4 figures, presented at 2007 CLEO conferenc
Single-photon detection timing jitter in a visible light photon counter
Visible light photon counters (VLPCs) offer many attractive features as
photon detectors, such as high quantum efficiency and photon number resolution.
We report measurements of the single-photon timing jitter in a VLPC, a critical
performance factor in a time-correlated single-photon counting measurement, in
a fiber-coupled closed-cycle cryocooler. The measured timing jitter is 240 ps
full-width-at-half-maximum at a wavelength of 550 nm, with a dark count rate of
25 000 counts per second. The timing jitter increases modestly at longer
wavelengths to 300 ps at 1000 nm, and increases substantially at lower bias
voltages as the quantum efficiency is reduced
The extended narrow-line region of two type-I quasi-stellar objects
We investigate the narrow-line region (NLR) of two radio-quiet QSOs,
PG1012+008 and PG1307+085, using high signal-to-noise spatially resolved
long-slit spectra obtained with FORS1 at the Very Large Telescope. Although the
emission is dominated by the point-spread function of the nuclear source, we
are able to detect extended NLR emission out to several kpc scales in both QSOs
by subtracting the scaled central spectrum from outer spectra. In contrast to
the nuclear spectrum, which shows a prominent blue wing and a broad line
profile of the [O III] line, the extended emission reveals no clear signs of
large scale outflows. Exploiting the wide wavelength range, we determine the
radial change of the gas properties in the NLR, i.e., gas temperature, density,
and ionization parameter, and compare them with those of Seyfert galaxies and
type-II QSOs. The QSOs have higher nuclear temperature and lower electron
density than Seyferts, but show no significant difference compared to type-II
QSOs, while the ionization parameter decreases with radial distance, similar to
the case of Seyfert galaxies. For PG1012+008, we determine the stellar velocity
dispersion of the host galaxy. Combined with the black hole mass, we find that
the luminous radio-quiet QSO follows the local M_BH-sigma* relation of active
galactic nuclei.Comment: 7 pages, 5 figures, accepted for publication in Ap
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