1,460 research outputs found
Observation of Interactions between Trapped Ions and Ultracold Rydberg Atoms
We report on the observation of interactions between ultracold Rydberg atoms
and ions in a Paul trap. The rate of observed inelastic collisions, which
manifest themselves as charge transfer between the Rydberg atoms and ions,
exceeds that of Langevin collisions for ground state atoms by about three
orders of magnitude. This indicates a huge increase in interaction strength. We
study the effect of the vacant Paul trap's electric fields on the Rydberg
excitation spectra. To quantitatively describe the exhibited shape of the ion
loss spectra, we need to include the ion-induced Stark shift on the Rydberg
atoms. Furthermore, we demonstrate Rydberg excitation on a dipole-forbidden
transition with the aid of the electric field of a single trapped ion. Our
results confirm that interactions between ultracold atoms and trapped ions can
be controlled by laser coupling to Rydberg states. Adding dynamic Rydberg
dressing may allow for the creation of spin-spin interactions between atoms and
ions, and the elimination of collisional heating due to ionic micromotion in
atom-ion mixtures.Comment: 7 pages, 5 figures, including appendices. Note that the title has
been changed in version
Trapped ions in Rydberg-dressed atomic gases
We theoretically study trapped ions that are immersed in an ultracold gas of
Rydberg-dressed atoms. By off-resonant coupling on a dipole-forbidden
transition, the adiabatic atom-ion potential can be made repulsive. We study
the energy exchange between the atoms and a single trapped ion and find that
Langevin collisions are inhibited in the ultracold regime for these repulsive
interactions. Therefore, the proposed system avoids recently observed ion
heating in hybrid atom-ion systems caused by coupling to the ion's radio
frequency trapping field and retains ultracold temperatures even in the
presence of excess micromotion.Comment: 9 pages, 5 figures including appendice
Observation of collisions between cold Li atoms and Yb ions
We report on the observation of cold collisions between Li atoms and
Yb ions. This combination of species has recently been proposed as the most
suitable for reaching the quantum limit in hybrid atom-ion systems, due to its
large mass ratio. For atoms and ions prepared in the ground state,
the charge transfer and association rate is found to be at least~10 times
smaller than the Langevin collision rate. These results confirm the excellent
prospects of Li--Yb for sympathetic cooling and quantum information
applications. For ions prepared in the excited electronic states ,
and , we find that the reaction rate is dominated by
charge transfer and does not depend on the ionic isotope nor the collision
energy in the range ~1--120~mK. The low charge transfer rate for ground
state collisions is corroborated by theory, but the shell in the Yb
ion prevents an accurate prediction for the charge transfer rate of the
, and states. Using \textit{ab initio}
methods of quantum chemistry we calculate the atom-ion interaction potentials
up to energies of 30~cm, and use these to give qualitative
explanations of the observed rates.Comment: 8 pages, 7 figures (including appendices
Searching for the pulsar in G18.95-1.1: Discovery of an X-ray point source and associated synchrotron nebula with Chandra
Using the Chandra X-ray Observatory, we have pinpointed the location of a
faint X-ray point source (CXOUJ182913.1-125113) and an associated diffuse
nebula in the composite supernova remnant G18.95-1.1. These objects appear to
be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point
source is best described by an absorbed powerlaw model with Gamma=1.6 and an
N_H of ~1x10^(22) cm^(-2). This model predicts a relatively low unabsorbed
X-ray luminosity of about L_X (0.5-8.0keV) = 4.1x10^(31)D_2^2 erg s^(-1), where
D_2 is the distance in units of 2kpc. The best-fitted model of the diffuse
nebula is a combination of thermal (kT = 0.48keV) and non-thermal (1.4 < Gamma
< 1.9) emission. The unabsorbed X-ray luminosity of L_X = 5.4x10^(33)D_2^2 erg
s^(-1) in the 0.5-8keV energy band seems to be largely dominated by the thermal
component from the SNR, providing 87% of L_X in this band. No radio or X-ray
pulsations have been reported for CXOUJ182913.1-125113. If we assume an age of
~5300yr for G18.95-1.1 and use the X-ray luminosity for the pulsar and the wind
nebula together with the relationship between spin-down luminosity (via
magnetic dipole radiation) and period, we estimate the pulsar's period to be P
= 0.4s. Compared to other rotation-powered pulsars, a magnetic field of
2.2x10^(13)G is implied by its location in the P-Pdot diagram, a value which is
close to that of the quantum critical field.Comment: 8 pages, 3 Figures, accepted for publication in Ap
Repetitive titin epitopes with a 42 nm spacing coincide in relative position with known A band striations also identified by major myosin-associated proteins. An immunoelectron-microscopical study on myofibrils.
A direct titin-thick filament interaction in certain regions of the A band is suggested by results using four new monoclonal antibodies specific for titin in immunoelectron microscopy. Antibodies T30, T31 and T32 identify quasi-repeats in the titin molecule characterized by a 42–43 nm repeat spacing. These stripes seem to coincide with striations established by others on negatively stained cryosections of the A band. Antibodies T30 and T32 recognize epitopes matching five or two of the seven striations per half sacromere known to harbor both the myosin-associated C-protein and an 86K (K = 10(3) Mr) protein. Antibody T31 labels two stripes in the P zone, which correspond to the two positions where decoration is seen with 86K protein, but not with C-protein. The single titin epitope defined by antibody T33 is located 55 nm prior to the center of the M band. This position seems to coincide with the M7 striation defined by others on negatively stained A bands. The T33 epitope position proves that the titin molecule, which is known to be anchored at the Z line, also penetrates into the complex architecture of the M band. The titin epitopes described here enable us to begin to correlate known ultrastructural aspects of the interior part of the A band with the disposition of the titin molecule in the sarcomere. They raise the question of whether there is a regular interaction pattern between titin and the thick filaments
Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR
We present spectral analysis of NuSTAR and Swift observations of Cep X-4
during its outburst in 2014. We observed the source once during the peak of the
outburst and once during the decay, finding good agreement in the spectral
shape between the observations. We describe the continuum using a powerlaw with
a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron
resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line
with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to
describe the shape of the CRSF accurately, leaving significant deviations at
the red side of the line. We characterize this asymmetry with a second
absorption feature around 19 keV. The line energy of the CRSF, which is not
influenced by the addition of this feature, shows a small but significant
positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep
X-4 is below the theoretical limit where such a correlation is expected. This
behavior is similar to Vela X-1 and we discuss parallels between the two
systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter
Моделирование реакционно-ректификационной колонны синтеза этил-трет-бутилового эфира (ЭТБЭ)
Die vorliegende fünfteilige Artikelserie beschreibt Konzepte und Anwendungen der Lasertechnik in der Fertigung. Aufbauend auf einer Erhebung des Anwendungspotentials werden Aspekte der Anlagen- und Prozessplanung sowie zugeschnittene Fertigungskonzepte diskutiert. Hieraus wird eine integrierte Vorgehensweise zur Einbindung in Systeme für die Qualitätssicherung und der Arbeitssicherheit abgeleitet
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