3,176 research outputs found
Efficient channeling of fluorescence photons from single quantum dots into guided modes of optical nanofiber
We experimentally demonstrate the efficient channeling of fluorescence
photons from single q-dots on optical nanofiber into the guided modes, by
measuring the photon-count rates through the guided and radiation modes
simultaneously. We obtain the maximum channeling efficiency to be 22.0
(\pm4.8)% at fiber diameter of 350 nm for the emission wavelength of 780 nm.
The results may open new possibilities in quantum information technologies for
generating single photons into single-mode optical-fibers.Comment: 5 pages, 4 figure
Analysis of previous microscopic calculations for second state in C in terms of 3-alpha particle Bose-condensed state
The wave function of the second state of C which was obtained
long time ago by solving the microscopic 3 problem is shown to be
almost completely equivalent to the wave function of the 3 condensed
state which has been proposed recently by the present authors. This equivalence
of the wave functions is shown to hold in two cases where different effective
two-nucleon forces are adopted. This finding gives strong support for
interpreting the second state of C which is the key state for the
synthesis of C in stars ('Hoyle' state), and which is one of the typical
mysterious states in light nuclei, as a gas-like structure of three
particles, Bose-condensed into an identical s-wave function.Comment: revtex, 5 pages, 2 figures, submitted to Phys. Rev.
Trapping of Neutral Rubidium with a Macroscopic Three-Phase Electric Trap
We trap neutral ground-state rubidium atoms in a macroscopic trap based on
purely electric fields. For this, three electrostatic field configurations are
alternated in a periodic manner. The rubidium is precooled in a magneto-optical
trap, transferred into a magnetic trap and then translated into the electric
trap. The electric trap consists of six rod-shaped electrodes in cubic
arrangement, giving ample optical access. Up to 10^5 atoms have been trapped
with an initial temperature of around 20 microkelvin in the three-phase
electric trap. The observations are in good agreement with detailed numerical
simulations.Comment: 4 pages, 4 figure
Alpha cluster condensation in 12C and 16O
A new -cluster wave function is proposed which is of the
-particle condensate type. Applications to C and O show
that states of low density close to the 3 resp. 4 -particle threshold
in both nuclei are possibly of this kind. It is conjectured that all
self-conjugate 4 nuclei may show similar features.Comment: 4 pages, 2 tables, 2 figure
Atom trapping and guiding with a subwavelength-diameter optical fiber
We suggest using an evanescent wave around a thin fiber to trap atoms. We
show that the gradient force of a red-detuned evanescent-wave field in the
fundamental mode of a silica fiber can balance the centrifugal force when the
fiber diameter is about two times smaller than the wavelength of the light and
the component of the angular momentum of the atoms along the fiber axis is in
an appropriate range. As an example, the system should be realizable for Cesium
atoms at a temperature of less than 0.29 mK using a silica fiber with a radius
of 0.2 m and a 1.3-m-wavelength light with a power of about 27 mW.Comment: 5 pages, 5 figure
Accuracy of B(E2; 0+ -> 2+) transition rates from intermediate-energy Coulomb excitation experiments
The method of intermediate-energy Coulomb excitation has been widely used to
determine absolute B(E2; 0+ -> 2+) quadrupole excitation strengths in exotic
nuclei with even numbers of protons and neutrons. Transition rates measured
with intermediate-energy Coulomb excitation are compared to their respective
adopted values and for the example of 26Mg to the B(E2; 0+ -> 2+) values
obtained with a variety of standard methods. Intermediate-energy Coulomb
excitation is found to have an accuracy comparable to those of long-established
experimental techniques.Comment: to be published in Phys. Rev.
Doping Dependence of Spin Dynamics in Electron-Doped Ba(Fe1-xCox)2As2
The spin dynamics in single crystal, electron-doped Ba(Fe1-xCox)2As2 has been
investigated by inelastic neutron scattering over the full range from undoped
to the overdoped regime. We observe damped magnetic fluctuations in the normal
state of the optimally doped compound (x=0.06) that share a remarkable
similarity with those in the paramagnetic state of the parent compound (x=0).
In the overdoped superconducting compound (x=0.14), magnetic excitations show a
gap-like behavior, possibly related to a topological change in the hole Fermi
surface (Lifshitz transition), while the imaginary part of the spin
susceptibility prominently resembles that of the overdoped cuprates. For the
heavily overdoped, non-superconducting compound (x=0.24) the magnetic
scattering disappears, which could be attributed to the absence of a hole
Fermi-surface pocket observed by photoemission.Comment: 6 pages, 5 figures, published versio
Neutron scattering study of magnetic ordering and excitations in the ternary rare-earth diborocarbide Ce^{11}B_2C_2
Neutron scattering experiments have been performed on the ternary rare-earth
diborocarbide CeBC. The powder diffraction experiment confirms
formation of a long-range magnetic order at K, where a
sinusoidally modulated structure is realized with the modulation vector . Inelastic excitation spectra in the
paramagnetic phase comprise significantly broad quasielastic and inelastic
peaks centered at and 65 meV.
Crystalline-electric-field (CEF) analysis satisfactorily reproduces the
observed spectra, confirming their CEF origin. The broadness of the
quasielastic peak indicates strong spin fluctuations due to coupling between
localized spins and conduction electrons in the paramagnetic phase. A
prominent feature is suppression of the quasielastic fluctuations, and
concomitant growth of a sharp inelastic peak in a low energy region below
. This suggests dissociation of the conduction and localized
electrons on ordering, and contrasts the presently observed incommensurate
phase with spin-density-wave order frequently seen in heavy fermion compounds,
such as Ce(RuLa)Si.Comment: accepted for publication in Phys. Rev.
Reconstructing the solar integrated radial velocity using MDI/SOHO
Searches for exoplanets with radial velocity techniques are increasingly
sensitive to stellar activity. It is therefore crucial to characterize how this
activity influences radial velocity measurements in their study of the
detectability of planets in these conditions. In a previous work we simulated
the impact of spots and plages on the radial velocity of the Sun. Our objective
is to compare this simulation with the observed radial velocity of the Sun for
the same period. We use Dopplergrams and magnetograms obtained by MDI/SOHO over
one solar cycle to reconstruct the solar integrated radial velocity in the Ni
line 6768 \AA. We also characterize the relation between the velocity and the
local magnetic field to interpret our results. We obtain a stronger redshift in
places where the local magnetic field is larger (and as a consequence for
larger magnetic structures): hence we find a higher attenuation of the
convective blueshift in plages than in the network. Our results are compatible
with an attenuation of this blueshift by about 50% when averaged over plages
and network. We obtain an integrated radial velocity with an amplitude over the
solar cycle of about 8 m/s, with small-scale variations similar to the results
of the simulation, once they are scaled to the Ni line. The observed solar
integrated radial velocity agrees with the result of the simulation made in our
previous work within 30%, which validates this simulation. The observed
amplitude confirms that the impact of the convective blueshift attenuation in
magnetic regions will be critical to detect Earth-mass planets in the habitable
zone around solar-like stars.Comment: 17 pages, 11 figures, accepted in Astronomy and Astrophysic
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