17,872 research outputs found
New broad 8Be nuclear resonances
Energies, total and partial widths, and reduced width amplitudes of 8Be
resonances up to an excitation energy of 26 MeV are extracted from a coupled
channel analysis of experimental data. The presence of an extremely broad J^pi
= 2^+ ``intruder'' resonance is confirmed, while a new 1^+ and very broad 4^+
resonance are discovered. A previously known 22 MeV 2^+ resonance is likely
resolved into two resonances. The experimental J^pi T = 3^(+)? resonance at 22
MeV is determined to be 3^-0, and the experimental 1^-? (at 19 MeV) and 4^-?
resonances to be isospin 0.Comment: 16 pages, LaTe
An Alternative Parameterization of R-matrix Theory
An alternative parameterization of R-matrix theory is presented which is
mathematically equivalent to the standard approach, but possesses features
which simplify the fitting of experimental data. In particular there are no
level shifts and no boundary-condition constants which allows the positions and
partial widths of an arbitrary number levels to be easily fixed in an analysis.
These alternative parameters can be converted to standard R-matrix parameters
by a straightforward matrix diagonalization procedure. In addition it is
possible to express the collision matrix directly in terms of the alternative
parameters.Comment: 8 pages; accepted for publication in Phys. Rev. C; expanded Sec. IV,
added Sec. VI, added Appendix, corrected typo
Shaking a Box of Sand
We present a simple model of a vibrated box of sand, and discuss its dynamics
in terms of two parameters reflecting static and dynamic disorder respectively.
The fluidised, intermediate and frozen (`glassy') dynamical regimes are
extensively probed by analysing the response of the packing fraction to steady,
as well as cyclic, shaking, and indicators of the onset of a `glass transition'
are analysed. In the `glassy' regime, our model is exactly solvable, and allows
for the qualitative description of ageing phenomena in terms of two
characteristic lengths; predictions are also made about the influence of grain
shape anisotropy on ageing behaviour.Comment: Revised version. To appear in Europhysics Letter
Quantum cooling and squeezing of a levitating nanosphere via time-continuous measurements
With the purpose of controlling the steady state of a dielectric nanosphere
levitated within an optical cavity, we study its conditional dynamics under
simultaneous sideband cooling and additional time-continuous measurement of
either the output cavity mode or the nanosphere's position. We find that the
average phonon number, purity and quantum squeezing of the steady-states can
all be made more non-classical through the addition of time-continuous
measurement. We predict that the continuous monitoring of the system, together
with Markovian feedback, allows one to stabilize the dynamics for any value of
the laser frequency driving the cavity. By considering state-of-the-art values
of the experimental parameters, we prove that one can in principle obtain a
non-classical (squeezed) steady-state with an average phonon number .Comment: 10 pages, 9 figures; v2: close to published versio
Split-sideband spectroscopy in slowly modulated optomechanics
Optomechanical coupling between the motion of a mechanical oscillator and a
cavity represents a new arena for experimental investigation of quantum effects
on the mesoscopic and macroscopic scale.The motional sidebands of the output of
a cavity offer ultra-sensitive probes of the dynamics. We introduce a scheme
whereby these sidebands split asymmetrically and show how they may be used as
experimental diagnostics and signatures of quantum noise limited dynamics. We
show split-sidebands with controllable asymmetry occur by simultaneously
modulating the light-mechanical coupling and - slowly and out
of-phase. Such modulations are generic but already occur in optically trapped
set-ups where the equilibrium point of the oscillator is varied cyclically. We
analyse recently observed, but overlooked, experimental split-sideband
asymmetries; although not yet in the quantum regime, the data suggests that
split sideband structures are easily accessible to future experiments
The InfraâRed Absorption Spectra of CH3OD and CH2DOD
The infraâred absorption spectra of CH3OD and CH2DOD between 2.5ÎŒ and 24ÎŒ have been examined with a KBr prism spectrometer, and with appropriate gratings. The observed bands represent all of the fundamental vibrations except the one of lowest frequency which is associated with torsional vibrations about the CâO bond. Since these molecules depart only slightly from axial symmetry, the bands, with the exception of three due to the hydroxyl radical, correspond in position and appearance to those of the methyl halides. The rotational structure for the 10ÎŒ band (v5) of CH3OD has been resolved, and partial resolution is obtained in some other bands. The band v5 in CH2DOD has two components arising probably from two forms of the molecule in which the hydroxyl D atom occupies different valleys of the threefold potential. The deformation vibration (v7) is single for CH3OD but has four components in CH2DOD, indicating a separation of levels which for the former molecule are degenerate. A comparison of the frequencies obtained with gaseous and liquid samples indicates large displacements of the bands arising from the hydroxyl valence and deformation vibrations, the former toward greater waveâlengths in the liquid, and the latter toward smaller waveâlengths.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70499/2/JCPSA6-6-9-563-1.pd
Cavity cooling a single charged nanoparticle
The development of laser cooling coupled with the ability to trap atoms and
ions in electromagnetic fields, has revolutionised atomic and optical physics,
leading to the development of atomic clocks, high-resolution spectroscopy and
applications in quantum simulation and processing. However, complex systems,
such as large molecules and nanoparticles, lack the simple internal resonances
required for laser cooling. Here we report on a hybrid scheme that uses the
external resonance of an optical cavity, combined with radio frequency (RF)
fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows
confinement in vacuum, avoiding instabilities that arise from optical fields
alone, and crucially actively participates in the cooling process. This system
offers great promise for cooling and trapping a wide range of complex charged
particles with applications in precision force sensing, mass spectrometry,
exploration of quantum mechanics at large mass scales and the possibility of
creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references,
new title, and supplementary information include
Glassy dynamics in granular compaction
Two models are presented to study the influence of slow dynamics on granular
compaction. It is found in both cases that high values of packing fraction are
achieved only by the slow relaxation of cooperative structures. Ongoing work to
study the full implications of these results is discussed.Comment: 12 pages, 9 figures; accepted in J. Phys: Condensed Matter,
proceedings of the Trieste workshop on 'Unifying concepts in glass physics
The Low Frequency Fundamental Band of Ethane at 12Ό
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70313/2/JCPSA6-10-2-146-1.pd
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