192 research outputs found
Quantum interference with molecules: The role of internal states
Recent experiments have shown that fullerene and fluorofullerene molecules
can produce interference patterns. These molecules have both rotational and
vibrational degrees of freedom. This leads one to ask whether these internal
motions can play a role in degrading the interference pattern. We study this by
means of a simple model. Our molecule consists of two masses a fixed distance
apart. It scatters from a potential with two or several peaks, thereby
mimicking two or several slit interference. We find that in some parameter
regimes the entanglement between the internal states and the translational
degrees of freedom produced by the potential can decrease the visibility of the
interference pattern. In particular, different internal states correspond to
different outgoing wave vectors, so that if several internal states are
excited, the total interference pattern will be the sum of a number of
patterns, each with a different periodicity. The overall pattern is
consequently smeared out. In the case of two different peaks, the scattering
from the different peaks will excite different internal states so that the path
the molecule takes become entangled with its internal state. This will also
lead to degradation of the interference pattern. How these mechanisms might
lead to the emergence of classical behavior is discussed.Comment: 12 pages, 4 eps figures, quality of figures reduced because of size
restriction
A scalable optical detection scheme for matter wave interferometry
Imaging of surface adsorbed molecules is investigated as a novel detection
method for matter wave interferometry with fluorescent particles. Mechanically
magnified fluorescence imaging turns out to be an excellent tool for recording
quantum interference patterns. It has a good sensitivity and yields patterns of
high visibility. The spatial resolution of this technique is only determined by
the Talbot gratings and can exceed the optical resolution limit by an order of
magnitude. A unique advantage of this approach is its scalability: for certain
classes of nano-sized objects, the detection sensitivity will even increase
significantly with increasing size of the particle.Comment: 10 pages, 4 figure
Thermal limitation of far-field matter-wave interference
We assess the effect of the heat radiation emitted by mesoscopic particles on
their ability to show interference in a double slit arrangement. The analysis
is based on a stationary, phase-space based description of matter wave
interference in the presence of momentum-exchange mediated decoherence.Comment: 8 pages, 2 figures; published versio
Integrated Atom Detector Based on Field Ionization near Carbon Nanotubes
We demonstrate an atom detector based on field ionization and subsequent ion
counting. We make use of field enhancement near tips of carbon nanotubes to
reach extreme electrostatic field values of up to 9x10^9 V/m, which ionize
ground state rubidium atoms. The detector is based on a carpet of multiwall
carbon nanotubes grown on a substrate and used for field ionization, and a
channel electron multiplier used for ion counting. We measure the field
enhancement at the tips of carbon nanotubes by field emission of electrons. We
demonstrate the operation of the field ionization detector by counting atoms
from a thermal beam of a rubidium dispenser source. By measuring the ionization
rate of rubidium as a function of the applied detector voltage we identify the
field ionization distance, which is below a few tens of nanometers in front of
nanotube tips. We deduce from the experimental data that field ionization of
rubidium near nanotube tips takes place on a time scale faster than 10^(-10)s.
This property is particularly interesting for the development of fast atom
detectors suitable for measuring correlations in ultracold quantum gases. We
also describe an application of the detector as partial pressure gauge.Comment: 7 pages, 8 figure
Calibration of a single atom detector for atomic micro chips
We experimentally investigate a scheme for detecting single atoms
magnetically trapped on an atom chip. The detector is based on the
photoionization of atoms and the subsequent detection of the generated ions. We
describe the characterization of the ion detector with emphasis on its
calibration via the correlation of ions with simultaneously generated
electrons. A detection efficiency of 47.8% (+-2.6%) is measured, which is
useful for single atom detection, and close to the limit allowing atom counting
with sub-Poissonian uncertainty
Colloquium: Quantum interference of clusters and molecules
We review recent progress and future prospects of matter wave interferometry
with complex organic molecules and inorganic clusters. Three variants of a
near-field interference effect, based on diffraction by material
nanostructures, at optical phase gratings, and at ionizing laser fields are
considered. We discuss the theoretical concepts underlying these experiments
and the experimental challenges. This includes optimizing interferometer
designs as well as understanding the role of decoherence. The high sensitivity
of matter wave interference experiments to external perturbations is
demonstrated to be useful for accurately measuring internal properties of
delocalized nanoparticles. We conclude by investigating the prospects for
probing the quantum superposition principle in the limit of high particle mass
and complexity.Comment: 19 pages, 13 figures; v2: corresponds to published versio
Calix[4]arene based α-aminophosphonates: Novel carriers for Zwitterionic amino acids transport
A series of calix[4]arene based α-aminophosphonates were synthesized by the Kabachnik-Fields reaction of the calixarene-diamine (either at lower or upper rim), diethyl phosphite and a carbonyl compound (acetone or cyclohexanone). These compounds exhibited remarkable selectivity as carriers for the membrane transport of the zwitterionic form of aromatic amino acids
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