17,633 research outputs found
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
Vibrational Assignments in Ethane
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70687/2/JCPSA6-7-4-277-1.pd
The B Neutrino Spectrum
Knowledge of the energy spectrum of B neutrinos is an important
ingredient for interpreting experiments that detect energetic neutrinos from
the Sun. The neutrino spectrum deviates from the allowed approximation because
of the broad alpha-unstable Be final state and recoil order corrections to
the beta decay. We have measured the total energy of the alpha particles
emitted following the beta decay of B. The measured spectrum is
inconsistent with some previous measurements, in particular with a recent
experiment of comparable precision. The beta decay strength function for the
transition from B to the accessible excitation energies in Be is fit to
the alpha energy spectrum using the R-matrix approach. Both the positron and
neutrino energy spectra, corrected for recoil order effects, are constructed
from the strength function. The positron spectrum is in good agreement with a
previous direct measurement. The neutrino spectrum disagrees with previous
experiments, particularly for neutrino energies above 12 MeV.Comment: 15 pages, 13 figures, 4 tables, submitted to Phys. Rev. C, typos
correcte
The InfraâRed Absorption Spectrum of Diborane
The infraâred absorption spectrum of diborane has been examined under high resolution from 3.7ÎŒ to 30ÎŒ with automatic recording grating spectrometers. The rotational fine structure in two bands of each of the three types characteristic of asymmetric top molecules has been measured. All results and observations are consistent with the conclusion that diborane has the bridge structure, and belongs to the same symmetry point group, Vh, as ethylene. The observation and structure of the band with center at 368.7 cmâ1 provides spectroscopic evidence that the molecule is nonâplanar, and makes more definite the assignment of fundamental frequencies. Data on all bands fit quite well the symmetric top approximation, since accidentally two principal moments of inertia are approximately the same, and calculations yield accurate values for certain rotational constants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70903/2/JCPSA6-18-5-698-1.pd
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
The InfraâRed Absorption Spectrum of Boron Trifluoride
The infraâred absorption spectrum of BF3 has been studied under high resolution from 400 cmâ1 to 3000 cmâ1. The active fundamentals v2, v3 and v4 and the overtone 2v3 have been observed. The parallel fundamental v2 has been partially resolved and the value of the moment of inertia A found to be 79Ă10â40 g cm2. The BâF distance is 1.29Ă10â8 cm. The isotope effect due to the two isotopes of boron was observed in all bands. The appearance of the unresolved bands v4 and 2v3 is shown to be greatly influenced by the interaction between vibration and rotation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70698/2/JCPSA6-7-7-455-1.pd
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