2,675 research outputs found
Interference stabilization of autoionizing states in molecular studied by time- and angular-resolved photoelectron spectroscopy
An autoionizing resonance in molecular N is excited by an ultrashort XUV
pulse and probed by a subsequent weak IR pulse, which ionizes the contributing
Rydberg states. Time- and angular-resolved photoelectron spectra recorded with
a velocity map imaging spectrometer reveal two electronic contributions with
different angular distributions. One of them has an exponential decay rate of
fs, while the other one is shorter than 10 fs. This observation is
interpreted as a manifestation of interference stabilization involving the two
overlapping discrete Rydberg states. A formalism of interference stabilization
for molecular ionization is developed and applied to describe the autoionizing
resonance. The results of calculations reveal, that the effect of the
interference stabilization is facilitated by rotationally-induced couplings of
electronic states with different symmetry.Comment: 8 pages, 6 figure
The New Heavy Mesons: A Status Report
A survey of the experimental, phenomenological, and theoretical status of the
new heavy mesons is presented. States discussed are the , ,
, , , X(3872), X(3940), Y(3940), Z(3930), and
Y(4260). Quark models for spectra, strong decays, and hadronic interactions are
reviewed and used to interpret the new states. New results for strong decay
models, bound state decays, mesonic molecules, properties of the X(3872), and
the chiral doublet model are also presented.Comment: 62 page, 40 figs, 16 tables. v3 corrects typos, adds references.
Version to appear in Physics Report
High-Resolution Photoelectron Spectroscopy of Molecules
Rotationally resolved photoelectron spectra can provide significant insight
into the underlying dynamics of molecular photoionization. Here, we
discuss and compare results of recent theoretical studies of rotationally
resolved photoelectron spectra with measurements for molecules such as
HBr, OH, NO, N_2, CO, H_2O, H_2CO, and CH_3. These studies reveal the
rich dynamics of quantum-state-specific studies of molecular photoionization
and provide a robust description of key spectral features resulting
from Cooper minima, autoionization, alignment, partial-wave mixing,
and interference in related experimental studies
Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
Molecular transitions recently discovered at redshift z_abs=2.059 toward the
bright background quasar J2123-0050 are analysed to limit cosmological
variation in the proton-to-electron mass ratio, mu=m_p/m_e. Observed with the
Keck telescope, the optical echelle spectrum has the highest resolving power
and largest number (86) of H_2 transitions in such analyses so far. Also,
(seven) HD transitions are used for the first time to constrain mu-variation.
These factors, and an analysis employing the fewest possible free parameters,
strongly constrain mu's relative deviation from the current laboratory value:
dmu/mu =(+5.6+/-5.5_stat+/-2.9_sys)x10^{-6}, indicating an insignificantly
larger mu in the absorber. This is the first Keck result to complement recent
null constraints from three systems at z_abs>2.5 observed with the Very Large
Telescope. The main possible systematic errors stem from wavelength calibration
uncertainties. In particular, distortions in the wavelength solution on echelle
order scales are estimated to contribute approximately half the total
systematic error component, but our estimate is model dependent and may
therefore under or overestimate the real effect, if present.
To assist future mu-variation analyses of this kind, and other astrophysical
studies of H_2 in general, we provide a compilation of the most precise
laboratory wavelengths and calculated parameters important for absorption-line
work with H_2 transitions redwards of the hydrogen Lyman limit.Comment: 15 pages, 8 figures (8 EPS files), 3 tables. Accepted by MNRAS. ArXiv
copy includes full version of Fig. 1 (additional 8 pages, 7 EPS files).
Complete version of Table 1 available at
http://astronomy.swin.edu.au/~mmurphy/pub.htm
Mechanics of Systems of Affine Bodies. Geometric Foundations and Applications in Dynamics of Structured Media
In the present paper we investigate the mechanics of systems of
affinely-rigid bodies, i.e., bodies rigid in the sense of affine geometry.
Certain physical applications are possible in modelling of molecular crystals,
granular media, and other physical objects. Particularly interesting are
dynamical models invariant under the group underlying geometry of degrees of
freedom. In contrary to the single body case there exist nontrivial potentials
invariant under this group (left and right acting). The concept of relative
(mutual) deformation tensors of pairs of affine bodies is discussed. Scalar
invariants built of such tensors are constructed. There is an essential novelty
in comparison to deformation scalars of single affine bodies, i.e., there exist
affinely-invariant scalars of mutual deformations. Hence, the hierarchy of
interaction models according to their invariance group, from Euclidean to
affine ones, can be considered.Comment: 50 pages, 4 figure
NONRADIATIVE-TRANSITIONS IN SEMICONDUCTORS
Non-radiative transitions affect many aspects of semiconductor performance. Normally they reduce device efficiency by suppressing luminescence, creating defects, reducing carrier lifetimes, or enhancing diffusion during operation. The present review surveys both the theoretical and practical understanding of non-radiative transitions. It includes general theoretical results and the associated ideas, with the emphasis on phonon-induced and defect Auger processes. Most of the purely formal aspects are omitted, but the points of principle where uncertainties remain are discussed. The review also covers the relation between basic theoretical studies and practical applied work on device degradation. This includes a description of the atomic processes involved in the more important mechanism of device deterioration and the theoretical understanding of the mechanism of these underlying processes. Finally, there is a survey of models proposed for 'killer' centres
- …