5,491 research outputs found
Spontaneous Dissociation of 85Rb Feshbach Molecules
The spontaneous dissociation of 85Rb dimers in the highest lying vibrational
level has been observed in the vicinity of the Feshbach resonance which was
used to produce them. The molecular lifetime shows a strong dependence on
magnetic field, varying by three orders of magnitude between 155.5 G and 162.2
G. Our measurements are in good agreement with theoretical predictions in which
molecular dissociation is driven by inelastic spin relaxation. Molecule
lifetimes of tens of milliseconds can be achieved close to resonance.Comment: 4 pages, 3 figure
A search for double beta decays of tin isotopes with enhanced sensitivity
A search for the various double beta decay modes of 124Sn and 112Sn has been
performed on 75 kg.days of data. New half-life limits for excited states in
124Sn have been obtained including a lower limit for the decay into the first
excited 2+ state of 124Te of T_half > 0.87e20 yrs (90% CL) and into the first
excited 0+ state of T_half > 1.08e20 yrs (90% CL). Ground state and excited
state transitions of 112Sn have also been experimentally explored. A limit for
the 2 neutrino double electron capture of T_half > 1.8e19 yrs (90% CL) is
obtained. The non-observation of de-excitation gammas from the 0+ at 1888.5keV
results in a lower half-life limit on the 0 neutrino double electron capture
decay of 112Sn of T_half > 0.8e19 yrs (90% CL), despite a possible resonant
enhancement of the decay rate due to degenerated states.Comment: 6 pages, 7 figures, updated analysis and tex
Microscopic theory of atom-molecule oscillations in a Bose-Einstein condensate
In a recent experiment at JILA [E.A. Donley et al., Nature (London) 417, 529
(2002)] an initially pure condensate of Rb-85 atoms was exposed to a specially
designed time dependent magnetic field pulse in the vicinity of a Feshbach
resonance. The production of new components of the gas as well as their
oscillatory behavior have been reported. We apply a microscopic theory of the
gas to identify these components and determine their physical properties. Our
time dependent studies allow us to explain the observed dynamic evolution of
all fractions, and to identify the physical relevance of the pulse shape. Based
on ab initio predictions, our theory strongly supports the view that the
experiments have produced a molecular condensate.Comment: 18 pages, 20 figure
Binaries in star clusters and the origin of the field stellar population
Many, possibly most, stars form in binary and higher-order multiple systems.
Therefore, the properties and frequency of binary systems provide strong clues
to the star-formation process, and constraints on star-formation models.
However, the majority of stars also form in star clusters in which the birth
binary properties and frequency can be altered rapidly by dynamical processing.
Thus, we almost never see the birth population, which makes it very difficult
to know if star formation (as traced by binaries, at least) is universal, or if
it depends on environment. In addition, the field population consists of a
mixture of systems from different clusters which have all been processed in
different ways.Comment: 16 pages, no figures. To appear as invited review article in a
special issue of the Phil. Trans. Royal Soc. A: Ch. 8 "Star clusters as
tracers of galactic star-formation histories" (ed. R. de Grijs). Fully peer
reviewed. LaTeX, requires rspublic.cls style fil
The EMF Model Transformation Framework
We present the EMF Model Transformation framework (EMT), which supports the rule-based modification of EMF models.
Model transformation rules are defined graphically and compiled into Java code to be used in model transformation applications
Mid-infrared quantum cascade detectors for applications inspectroscopy and pyrometry
In this paper, we give an overview of quantum cascade detector technology for the near- and mid-infrared wavelength range. Thanks to their photovoltaic operating principle, the most advanced quantum cascade detectors offer great opportunities in terms of high detection speed, reliable room temperature operation, and excellent Johnson noise limited detectivity. Besides some important features dealing with their fabrication and their general characteristics, we will also briefly present some possibilities for performance improvement. Elementary theoretical considerations adopted from photoconductive detectors confirm that optimization of such devices always involves various trade-off
A microscopic quantum dynamics approach to the dilute condensed Bose gas
We derive quantum evolution equations for the dynamics of dilute condensed
Bose gases. The approach contains, at different orders of approximation, for
cases close to equilibrium, the Gross Pitaevskii equation and the first order
Hartree Fock Bogoliubov theory. The proposed approach is also suited for the
description of the dynamics of condensed gases which are far away from
equilibrium. As an example the scattering of two Bose condensates is discussed.Comment: 8 pages, submitted to Phys. Rev.
An absolute quantum energy inequality for the Dirac field in curved spacetime
Quantum Weak Energy Inequalities (QWEIs) are results which limit the extent
to which the smeared renormalised energy density of a quantum field can be
negative. On globally hyperbolic spacetimes the massive quantum Dirac field is
known to obey a QWEI in terms of a reference state chosen arbitrarily from the
class of Hadamard states; however, there exist spacetimes of interest on which
state-dependent bounds cannot be evaluated. In this paper we prove the first
QWEI for the massive quantum Dirac field on four dimensional globally
hyperbolic spacetime in which the bound depends only on the local geometry;
such a QWEI is known as an absolute QWEI
A RESPONSE TO COMMUNITY QUESTIONS ON THE MARINE20 RADIOCARBON AGE CALIBRATION CURVE: MARINE RESERVOIR AGES AND THE CALIBRATION OF 14C SAMPLES FROM THE OCEANS
ABSTRACT
Radiocarbon (14C) concentrations in the oceans are different from those in the atmosphere. Understanding these ocean-atmospheric 14C differences is important both to estimate the calendar ages of samples which obtained their 14C in the marine environment, and to investigate the carbon cycle. The Marine20 radiocarbon age calibration curve is created to address these dual aims by providing a global-scale surface ocean record of radiocarbon from 55,000–0 cal yr BP that accounts for the smoothed response of the ocean to variations in atmospheric 14C production rates and factors out the effect of known changes in global-scale palaeoclimatic variables. The curve also serves as a baseline to study regional oceanic 14C variation. Marine20 offers substantial improvements over the previous Marine13 curve. In response to community questions, we provide a short intuitive guide, intended for the lay-reader, on the construction and use of the Marine20 calibration curve. We describe the choices behind the making of Marine20, as well as the similarities and differences compared with the earlier Marine calibration curves. We also describe how to use the Marine20 curve for calibration and how to estimate ΔR—the localized variation in the oceanic 14C levels due to regional factors which are not incorporated in the global-scale Marine20 curve. To aid understanding, illustrative worked examples are provided.</jats:p
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