Author name code: cooper
ADS astronomy entries on 2022-09-14
=author:"Cooper, J." year:1965-1995
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Title: The Space Physics Data System - Cosmic and Heliospheric Nodes
Authors: Garrard, T. L.; Cooper, J.; Cummings, A.; Gazis, P.; Guzik,
T. G.; Kurth, W.; Lazarus, A.; McNutt, R.; Pyle, R.; Smith, C. W.
Bibcode: 1995icrc...24...84G
Altcode:
No abstract at ADS
Title: Collisional Interference in the Rotational Spectrum of HD-He
Authors: Tabisz, G. C.; McQuarrie, B.; Gao, B.; Cooper, J.
Bibcode: 1995ASPC...81..312T
Altcode: 1995lahr.conf..312T
No abstract at ADS
Title: Rotational spectrum of HD perturbed by He or Ar gases: The
effects of rotationally inelastic collisions on the interference
between allowed and collisionally induced components
Authors: Gao, Bo; Cooper, J.; Tabisz, G. C.
Bibcode: 1992PhRvA..46.5781G
Altcode:
The spectral line shapes for the HD rotational spectra perturbed by He
and Ar gases, which show interference between allowed and collisionally
induced dipole transitions, are calculated including the effects of
inelastic rotational collisions. The general parametrization of the
line shape, including inelastic collisions, requires six independent
real parameters as opposed to four in the theory of Herman, Tipping,
and Poll [Phys. Rev. A 20, 2006 (1979)]. Semiclassical calculations
based on classical trajectories indicate the importance of the
inelastic effects and show qualitative agreement with the experimental
parameters. However, it is clear that a full explanation of experimental
data will eventually require a full quantum treatment.
Title: Spectral line shape arising from collisional interference
between electric-dipole-allowed and collision-induced transitions
Authors: Gao, B.; Tabisz, G. C.; Trippenbach, M.; Cooper, J.
Bibcode: 1991PhRvA..44.7379G
Altcode:
A theory is developed to describe the spectral line shape due to
interference between electric-dipole-allowed and collision-induced
transitions in pure rotational molecular spectra. Motivation was
provided by experimental data available for HD-inert gas systems. This
theory is based on a master-equation approach to induced spectra
employed by Alber and Cooper [Phys. Rev. A 33, 3084 (1986)]. The active
molecule is considered to be immersed in a bath of perturbers. An
expression for the absorption coefficient is obtained within the binary
collision approximation that contains terms due to allowed, induced,
and interference contributions. Effects due to m mixing, J mixing,
and successive collisions are included. Low-order approximations of
the theory eventually reduce to results of earlier efforts, namely, the
pioneering description of collisional interference by Herman, Tipping,
and Poll [Phys. Rev A 20, 2006 (1979)] and refinements to it through
consideration of rotational level mixing. The principal attribute
of this approach is the treatment of allowed and collision-induced
transitions in a consistent manner.
Title: Estimation of ion velocity and temperature from asymmetric
model incoherent scatter spectra
Authors: Cooper, J.; Kohl, H.
Bibcode: 1990JATP...52..483C
Altcode:
A simple relaxation collision model is used to obtain line-of-sight ion
velocity distributions and incoherent scatter spectra for ion-neutral
collision frequency of comparable order to the ion gyro-frequency and
crossed electric and magnetic fields. The deduced Doppler shift and
Maxwellian temperature estimates are compared with the line-of-sight
ion mean velocities and plasma temperatures in the model. The spectrum
parameter estimates arise from the fitting of a Maxwellian spectrum to
the relaxation model spectrum using standard procedures. The deviation
of these estimates from the given parameters of the ion velocity
distribution for different electric field strengths and directions of
observation are discussed. Spectrum estimates depart most from plasma
parameters for viewing directions across the electric field.
Title: An overview of the ion dynamic effect in line broadening,
and a generalization of the unified theory.
Authors: Kelleher, D. E.; Oza, D. H.; Cooper, J.; Greene, R. L.
Bibcode: 1990JQSRT..44..101K
Altcode:
The authors present a brief overview of the collisional broadening
of hydrogenic radiators in thermal plasmas. Their focus is on
lines with unshifted central components, particularly the alpha
lines (Δn = 1), for which ion motion effects can be very large. The
calculations span a wide range of electron densities, temperatures, and
radiator-ion perturber reduced masses μ. The computations were made
using a numerical simulation approach. Numerical methods have proven
nesessary to deal with the overlapping strong collisions of different
ion perturbers. Most current analytical methods, such as the unified
theory, are not valid when strong collisions overlap, as is often the
case with ion perturbers. The authors are developing a generalization
of the unified theory which endeavors to overcome this limitation.
Title: Asymmetric incoherent scatter spectra from a relaxation
collision model
Authors: Cooper, J.; Kohl, H.
Bibcode: 1990JATP...52..133C
Altcode:
A relaxation collision model for ion flow through a stationary
neutral gas has been used to obtain ion velocity distributions and
line-of-sight incoherent scatter spectra for a range of values of
collision frequency and electric field. The mean velocity of the
line-of-sight ion velocity distribution has been compared with the
Doppler shift of the corresponding spectra. The latter is not always
a good estimate of the former, because the ion velocity distribution
in the plane perpendicular to the magnetic field direction is highly
distorted. For ion-neutral collision frequency to ion gyrofrequency
ratios (IGRs) 0.1-0.5, the greatest inaccuracies in mean velocity
estimation take place along the electric field direction, while for
IGRs = 0.5-1.0 the greatest inaccuracies occur across the electric field
direction. These inaccuracies would be reduced but not eliminated in a
more realistic model. At F-region altitudes, other processes must be
invoked to explain observed asymmetrical spectra, but the comparison
of mean line-of-sight ion velocity and spectrum Doppler shift may
still have relevance.
Title: Approximate Formulation of Redistribution in the LY alpha ,
LY beta , H alpha System
Authors: Cooper, J.; Ballagh, R. J.; Hubeny, I.
Bibcode: 1989ApJ...344..949C
Altcode:
Simple approximate formulas are given for the coupled redistribution of
Ly-alpha, Ly-beta, and H-alpha, by using well-defined approximations to
an essentially exact formulation. These formulas incorporate all the
essential physics including Raman scattering, lower state radiative
decay, and correlated terms representing emission during a collision
which must be retained in order that the emission coefficients are
properly behaved in the line wings. Approximate expressions for
the appropriate line broadening parameters are collected. Finally,
practical expressions for the source functions are given. These are
formulated through newly introduced nonimpact redistribution functions,
which are shown to be reasonably approximated by existing (ordinary
and generalized) redistribution functions.
Title: Redistribution in astrophysically important hydrogen lines
Authors: Cooper, J.; Ballagh, R. J.; Hubeny, I.
Bibcode: 1989STIN...8924251C
Altcode:
Under typical solar chromospheric conditions for hydrogen radiators,
strong collisions due to both electrons and ions are well separated in
time, so that a binary collision theory for collisional redistribution
is applicable. However, a simple impact approximation may not be
used, but rather a unified type theory is required in which frequency
dependent line shape parameters are used to describe both impact and
quasi-static regions of the spectrum. In addition, correlated terms
which describe absorption and emission during a collision are important,
and, in fact, without correlated terms describing both transfer of
excitation and emission during the same collision unphysical predictions
(such as negative intensities) would be obtained. In this paper theory
is specifically developed for the coupled Lyman-alpha, Lyman-beta,
Hydrogen-alpha system, and equations of statistical equilibrium and
absorption and emission coefficients are given. All correlated events
are examined and emission during a collision is found to be important
in the line wings. Stimulated emission and absorption is also included
within a broadband approximation. The major approximation is to ignore
lower state interaction. It is found that for Lyman-beta Raman-coupling
with Hydrogen-alpha occurs and the overall scattering of radiation in
the line wings is mostly coherent. In contrast, for Hydrogen-alpha,
incoherent redistribution due to lower state radiative decay (which
occurs even in the absence of collisions) is found to dominate
the coherent scattering. Finally, in the Lyman series the dominant
incoherent contribution is associated with cascade transitions and
inelastic collisions between different principal quantum states.
Title: Transfer and Redistribution of Polarized Light in Resonance
Lines. I. Quantum Formulation with Collisions
Authors: Streater, A.; Cooper, J.; Rees, D. E.
Bibcode: 1988ApJ...335..503S
Altcode:
Equations are derived quantum mechanically for the radiative transfer
of polarized light and statistical equilibrium governing the formation
of resonance lines in nonhydrogenic species. Redistribution due
to collisions is specifically included, but magnetic fields are
neglected. The formulation accounts for excited level interference
and optical pumping and is applicable to solar resonance lines such
as Ca II H and K and Mg II h and k.
Title: Experiments on time-dependent radiative transfer in a
spectral line.
Authors: Streater, A.; Molander, W.; Cooper, J.
Bibcode: 1988JQSRT..40..101S
Altcode:
The spatial and temporal evolution of excited atoms in an optically
thick magnesium vapor after an initial pulsed laser excitation
is measured using a delayed pulsed probe laser. The collisional
environment of the magnesium atoms in the vapor is modified by an
argon buffer gas. Angle-averaged partial and complete redistribution
calculations are presented and compared with the data. Other aspects
of the radiative transfer process are discussed.
Title: Direct probing of the radiation field in optically thick
environments.
Authors: Streater, A.; Cooper, J.
Bibcode: 1988JQSRT..39...49S
Altcode:
The directional dependence of escaping resonance radiation after an
initial excitation in an optically thick atomic magnesium vapor is
measured using a small sapphire rod as a probe. The rod acts as a
light pipe to bring the radiation directly out from deep within the
vapor. The time-dependent signal is observed in various directions
relative to the initial excitation and a significant anisotropy is
observed, especially at early times. The anisotropy is not strongly
dependent on the argon buffer gas pressure, and is greater further
from the initial excitation. The signal is compared with a calculated
signal under the assumption of complete redistribution.
Title: Unified description of radiative and dielectronic
recombination, including the coupling between autoionization and
radiation continua
Authors: Jacobs, V. L.; Cooper, J.; Haan, S. L.
Bibcode: 1987PhRvA..36.1093J
Altcode:
A unified description of radiative and dielectronic recombination
is presented that incorporates a nonperturbative treatment of the
electromagnetic coupling between the autoionization and radiative
decay continua. Particular attention is given to the angular
momentum degeneracy of the atomic levels and to the multiplicity of
angular momentum components in the partial-wave expansion for the
electron-continuum state. Through the introduction of vertex functions
and of a modified propagator, the S matrix describing the combined
electron-ion photorecombination process is expressed as the sum of
a resonant and a nonresonant transition amplitude. Future extensions
to incorporate multicontinuum-channel recombination, the effects of
overlapping autoionizing resonances, renormalization, and the effects
of collisional dephasing processes and plasma electric microfields
are discussed.
Title: Solar Neutron Emissivity during the Large Flare on 1982 June 3
Authors: Chupp, E. L.; Debrunner, H.; Flueckiger, E.; Forrest, D. J.;
Golliez, F.; Kanbach, G.; Vestrand, W. T.; Cooper, J.; Share, G.
Bibcode: 1987ApJ...318..913C
Altcode:
For the solar neutron event on June 3, 1982, it is shown here that
the combined SMM Gamma Ray Spectrometer and Jungfraujoch neutron
monitor data require a time-extended emission of neutrons at the sun
with energies of 100 MeV to about 2 GeV. The solar neutron emissivity
spectrum is shown to have a strong downward curvature or truncation
between 2 and 4 GeV. A Bessel function and truncated power law give
acceptable fits to the observational data, but only the power law can
explain the rapid rise of the neutron monitor count rate. The integrated
emissivity of neutrons above E(n) of 100 MeV is strongly constrained
at 8 x 10 to the 28th neutrons/sr and is essentially independent
of neutron spectral shape. At neutron energies of about 100 MeV,
good agreement is found for both spectral forms with observations of
neutron decay protons.
Title: On time-dependent radiative transfer.
Authors: Streater, A.; Cooper, J.; Sandle, W.
Bibcode: 1987JQSRT..37..151S
Altcode:
An integral equation is developed for application to time-dependent
laboratory experiments in which partial redistribution effects
are important. The equation of transport with the Heasley-Kneer
emission coefficient and the equation of statistical equilibrium
lead to a time-dependent redistribution function containing an
absorption-re-emission term which decays exponentially in time and a
scattering term which is instantaneous. This integral equation does
not agree with an equation written by Payne et al. that has been used
to compare theory with experiments.
Title: Observation of radiative transfer of polarized light.
Authors: Belsley, M.; Streater, A.; Burnett, K.; Ewart, P.; Cooper, J.
Bibcode: 1986JQSRT..36..163B
Altcode:
The results of an experiment sensitive to polarization and
angle-dependent effects of resonance line radiation transport
in a collisional environment are presented. Having measured both
the excited atomic state population and alignment as a function of
distance from the initial excitation, considerable anisotropy in the
alignment is found. Included in the discussion are the results of an
angle-average model calculation, which allows the authors to point out,
in a qualitatively way, some of the important physics of the problem.
Title: Redistribution of Radiation in the Presence of
Velocity-changing Collisions
Authors: Hubeny, I.; Cooper, J.
Bibcode: 1986ApJ...305..852H
Altcode:
Starting with the recent work of Cooper et al., a suitable form
of the normalized redistribution function relevant for a treatment
of redistribution in the presence of velocity-changing collisions
is presented. Attention is devoted to provide practical estimates
of the ratio between the usual line-broadening parameters and the
velocity-changing rate. It is shown that for virtually all cases of
astrophysical interest the effect of velocity-changing collisions is
quite negligible.
Title: Very energetic gamma-rays from the 3 June 1982 solar flare
Authors: Forrest, D. J.; Vestrand, W. T.; Chupp, E. L.; Rieger, E.;
Cooper, J.; Share, G. H.
Bibcode: 1986AdSpR...6f.115F
Altcode: 1986AdSpR...6..115F
The Gamma-Ray Spectrometer on the Solar Maximum Mission satellite has
recorded high energy gamma-ray and neutron emission from the flare on
3 June 1982. During the 65 sec. impulsive phase the gamma rays >
10 MeV contains emissions from both primary electron bremsstrahlung
and nuclear pion decay. Hence the impulsive phase acceleration process
must produce both primary electrons with energies > 60 MeV and ions
>500 MeV. This flare also has a extended emission phase lasting more
than 1000 sec which is most easily observed at gamma-ray energies >
10 MeV. After removing the counting rates from the more slowly moving
neutrons produced at earlier times, the resulting gamma ray spectrum can
be entirely explained by nuclear pion production. We find that >70 %
of the pions were produced in the extended emission phase. In contrast,
more than 70 % of the high energy primary electron bremsstrahlung
and the < 30 MeV ion produced nuclear line emission occured in the
65 sec impulsive phase. This represents the first clear observation
of a new acceleration process which produces a electron deficient,
very hard ion spectrum extending beyond 1000 MeV.
Title: The classification of distorted-mirror reflections and its
ionospheric modification due to the underlying ionization
Authors: Cummack, C. H.; Cooper, J.
Bibcode: 1986JATP...48...51C
Altcode:
A systematic classification of reflections from a sinusoidally
distorted-mirror has led to the identification of three classes of rays;
direct simple rays which hit the mirror once on reflection; direct
complex rays which hit the mirror several times before reflection;
indirect rays which leave from and return to the source at different
angles. The conditions on the distortion amplitude, wavelength and
height for the different classes to exist are obtained. A comparison of
results is made with those from a Chapman layer with a sinusoidally
varying height of peak density, in the absence of any magnetic
field. The broad classification of solutions is preserved, but direct
and indirect rays are no longer independent and at large scale heights
the presence of underlying ionization removes some solutions. The
construction of ionograms of these profiles shows that indirect and
complex direct rays contribute significantly to the traces observed.
Title: Effect of quasi-bound states on collisional redistribution.
Authors: Belsley, M.; Alford, W. J.; Burnett, K.; Cooper, J.
Bibcode: 1986JQSRT..35...53B
Altcode:
The authors derive an expression for the collisional redistribution of
radiation due to states trapped by an excited state potential barrier
in the limit of no subsequent collisions during the excited state
lifetime. By considering two simple models, the authors suggest three
possible methods of qualitatively determining excited state well depths
when no detailed knowledge of the ground or excited state interaction
potentials exists a priori.
Title: The analysis of a travelling ionospheric disturbance with
non-linear ionization response
Authors: Cooper, J.; Cummack, C. H.
Bibcode: 1986JATP...48...61C
Altcode:
Ionograms from a triangular array of ionosondes, are analyzed to yield
the characteristics of an internal gravity wave throughout the F-region
overlays, which measure the shape of the ionogram near the F1-cusp, give
a good estimate of wave amplitude. An internal gravity wave generates
a non-linear response in the ionospheric electron density profiles,
which have the characteristics of thick ledges. The ionograms show
external hooks associated with such ledges.
Title: Two-photon collisional redistribution of radiation
Authors: Alber, G.; Cooper, J.
Bibcode: 1985PhRvA..31.3644A
Altcode:
Collisional redistribution in the presence of two weakly exciting
laser fields is studied, including the effects due to degeneracy of
the radiator states. A general expression for the total redistributed
intensity is derived valid for arbitrary detunings and polarizations
of the exciting laser fields. In particular, this expression contains
all single-collision and sequential-collision contributions, which
are equally important under certain circumstances. The similarities
and differences between the redistributed intensity as calculated
in this paper and the collisionally aided radiative excitation cross
sections studied by Yeh and Berman (1979) and Light and Szoke (1978)
are pointed out.
Title: Redistribution of radiation in the absence of collisions
Authors: Lombardi, G. G.; Kelleher, D. E.; Cooper, J.
Bibcode: 1985ApJ...288..820L
Altcode:
Redistribution and depolarization of near-resonant radiation is
studied for the He 2(1P)-3(1D) line (668 nm) and some data for
H-alpha (656 nm) are also presented. A Nd:YAG pumped dye laser, with
a bandwidth of 0.1/cm and a power density of 100 kW/sq cm, is used in
the experiment. The transitions have lower levels with natural line
widths that are large compared with their upper-level natural widths,
and, under experimental conditions, their collisional widths are also
small. The ratio of fluorescence to Rayleigh intensity is measured
and the results indicate that while the Rayleigh emission has the same
temporal development as the laser pulse (5 ns FWHM), the fluorescent
intensity has a decay time determined by the radiative decay lifetime
and by collisional quenching. The prediction that redistribution of
radiation occurs in the absence of collisions for transitions having
significant lower-level radiative widths is confirmed. Depolarization
rates by collisions with helium are also inferred from the measurements.
Title: Collisional redistribution of light: Far-wing line shapes
and polarizations for the Ba-(Ar,Xe) systems
Authors: Alford, W. J.; Andersen, N.; Burnett, K.; Cooper, J.
Bibcode: 1984PhRvA..30.2366A
Altcode:
The far-wing collisional redistribution line shape, the redistributed
fluorescence polarization, and the collisional alignment decay rates
have been measured for barium perturbed by argon and xenon. The
experiment was performed with a heated gas cell (T = 900 K) with
perturber-gas densities in the 1-30-torr range and laser light
detuned + or - 3-1000/cm from the 5535-A Ba I 6(1)S-6(1)P resonance
line. Metal-vapor densities were determined by a Rayleigh scattering
technique which is outlined in detail. By correlating structure
in the line shape with that of the polarization, it is possible to
make definitive statements about the interatomic potentials. The Ba
data show strong similarities with previous experimental results for
similar two-electron atoms, namely Ca, Sr, and Hg, and so the present
conclusions are of relevance to these systems as well.
Title: Properties of Flares Having Emission > 10 MeV
Authors: Forrest, D. J.; Vestrand, W. T.; Rieger, E.; Cooper, J.;
Chupp, E. L.; Share, G.
Bibcode: 1984BAAS...16Q.475F
Altcode:
No abstract at ADS
Title: Radiative transfer equations in broad-band, time-varying fields
Authors: Cooper, J.; Zoller, P.
Bibcode: 1984ApJ...277..813C
Altcode:
A derivation of the equation of transfer is obtained by starting with
Maxwell's equations in the "slowly varying envelope" form. Particular
attention is paid to characterizing the intensity that is "seen" by
the atom (which is found to be related to a Wigner distribution of
the electric field). The equation of transfer is found to be valid for
"broad-band" slowly varying radiation fields.
Title: On the line profile coefficient for stimulated emission
Authors: Cooper, J.; Hubeny, I.; Oxenius, J.
Bibcode: 1983A&A...127..224C
Altcode:
It is pointed out that the line profile coefficients for spontaneous and
stimulated emission are identical in low-intensity radiation fields. In
more intense radiation fields, however, the stimulated emission profiles
in the radiative transfer equation and in the rate equations for the
atomic level populations may differ from each other, owing to their
different physical nature. A seeming discrepancy between the stimulated
emission profiles of the usual semi-classical approach and a recent
quantum mechanical approach by Cooper et al. (1982), which should
also be valid for intense "broadband" fields, is discussed and shown
to have negligible consequences for low-intensity radiation fields.
Title: Polarization of collisionally redistributed light from the
far wings of strontium-rare-gas systems
Authors: Alford, W. J.; Burnett, K.; Cooper, J.
Bibcode: 1983PhRvA..27.1310A
Altcode:
We have made systematic measurements of the polarization of fluorescence
from Sr-rare-gas systems excited off resonance by linearly polarized
light. Measurements of this type give information about the evolution
during a collision after the absorption of a photon. This information
is important in obtaining and verifying aspects of the interaction
potential that cannot be studied using conventional line-broadening
experiments. We have also measured the collisional-alignment decay
rates for Sr-rare-gas systems by observing the perturber-pressure
dependence of the polarization of the fluorescence. To the best of
our knowledge this is a new technique for measuring these decay rates.
Title: Theory of time-dependent intense-field collisional resonance
fluorescence
Authors: Kleiber, P. D.; Cooper, J.; Burnett, K.; Kunasz, C. V.;
Raymer, M. G.
Bibcode: 1983PhRvA..27..291K
Altcode:
The time-dependent theory of Courtens and Szoke (1977) is generalized
using the approach of Burnett et al. (1982) to derive time-dependent
spectral intensities of resonance fluorescence from atoms driven by a
pulsed laser in the presence of collisions. These results are valid
both for laser detunings inside and outside the usual impact region
of the spectrum, including Zeeman degeneracy effects. This theory is
applied to a simple but important example (J = 0 to J = 1) to obtain
quantitative predictions for the observable scattered-light spectrum
which can be directly compared with recent experiments.
Title: On redistribution and the equations for radiative transfer
Authors: Cooper, J.; Ballagh, R. J.; Burnett, K.; Hummer, D. G.
Bibcode: 1982ApJ...260..299C
Altcode:
The derivation of the equations of statistical equilibrium are
outlined, starting from the quantum density-matrix equations,
drawing particular attention to the approximations and assumptions
used in the development of tractable expressions. Then, using the
quantum-fluctuation-regression theorem, emission and absorption
coefficients are obtained for multilevel atomic systems which are
nondegenerate except for m-substates. These coefficients are valid to
first order in the incident intensity. Possible extensions to higher
intensity broadband incoherent fields are suggested.
Title: Comment on the use of an exponential approximation for the
Stark broadening of hydrogen lines.
Authors: Cooper, J.; Smith, E. W.
Bibcode: 1982JQSRT..27..665C
Altcode:
No abstract at ADS
Title: Redistribution of radiation for the wings of Lyman-alpha
Authors: Yelnik, J. -B.; Burnett, K.; Cooper, J.; Ballagh, R. J.;
Voslamber, D.
Bibcode: 1981ApJ...248..705Y
Altcode:
Earlier work on redistribution of radiation by collisions for isolated
lines is extended to overlapping lines, and an explicit expression for
the frequency redistribution is given for Lyman-alpha. This expression
is valid, even when the emitted photon is in the (non-impact) line
wings. A simple physical explanation of the result is possible.
Title: An analysis of Markovian model microfield methods for Stark
broadening.
Authors: Smith, E. W.; Talin, B.; Cooper, J.
Bibcode: 1981JQSRT..26..229S
Altcode:
No abstract at ADS
Title: Collisional redistribution of radiation. I. The density matrix
Authors: Burnett, K.; Cooper, J.; Ballagh, R. J.; Smith, E. W.
Bibcode: 1980PhRvA..22.2005B
Altcode:
As a first step in deriving accurate, calculable expressions for
collisional redistribution of radiation, valid outside the impact
regime a method for calculating an accurate binary-collision density
operator for an atom in the presence of a driving field and perturbers
is presented. Projection-operator techniques to establish first
the precise validity of the Markoff approximation for radiative
relaxation are used. Using the same techniques, it is shown how the
collisional-relaxation problem may be analyzed in a practical manner
outside the Markoff approximation. The effect of correlations between
radiative and collisional events is included in a consistent way and
the physical implications of these correlation effects are demonstrated
for a simple example, the two-level atom with nondegenerate levels.
Title: Collisional redistribution of radiation. III. The equation
of motion for the correlation function and the scattered spectrum
Authors: Burnett, K.; Cooper, J.
Bibcode: 1980PhRvA..22.2044B
Altcode:
Computations were made of the scattering of monochromatic radiation
by a degenerate atom in the binary-collision approximation for field
strengths whose products of the Rabi frequency for atomic transition and
the duration of a strong collision are much less than 1. An expression
of motion for the correlation function is derived which does not exclude
the region where thermal correlations may be neglected; the equation is
valid outside the quantum-regression regime, and has a straightforward
solution for practical cases. Solutions for the weak-field linear
response regime are presented in terms of generalized absorption and
emission profiles which depend on the indices of the atomic multipoles.
Title: Collisional redistribution of radiation. II. The effects of
degeneracy on the equations of motion for the density matrix
Authors: Burnett, K.; Cooper, J.
Bibcode: 1980PhRvA..22.2027B
Altcode:
The effect of correlations between an absorber atom and perturbers
in the binary-collision approximation are applied to degenerate
atomic systems. A generalized absorption profile which specifies
the final state of the atom after an absorption event is related to
the total intensities of Rayleigh scattering and fluorescence from
the atom. It is suggested that additional dynamical information to
that obtainable from ordinary absorption experiments is required in
order to describe redistributed atomic radiation. The scattering
of monochromatic radiation by a degenerate atom is computed in a
binary-collision approximation; an equation of motion is derived for
the correlation function which is valid outside the quantum-regression
regime. Solutions are given for the weak-field conditions in terms
of generalized absorption and emission profiles that depend on the
indices of the atomic multipoles.
Title: Observation of dynamic correlations in collisional
redistribution and depolarization of light
Authors: Thomann, P.; Burnett, K.; Cooper, J.
Bibcode: 1980PhRvL..45.1325T
Altcode:
Theory shows that to explain the polarization of light collisionally
redistributed from the far line wings of an atomic transition, one must
consider correlated events in which absorption during a collision,
and propagation to the final Zeeman-state superposition at the end
of the collision is important. Polarizations of up to about 40% have
been measured in the far line wings, substantially confirming this
prediction, and showing that scattering experiments cannot just be
characterized by simple absorption or emission profiles.
Title: Zeeman degeneracy effects in collisional intense-field
resonance fluorescence
Authors: Cooper, J.; Ballagh, R. J.; Burnett, K.
Bibcode: 1980PhRvA..22..535C
Altcode:
Resonance fluorescence due to intense laser fields from
a Zeeman degenerate atom being perturbed by collisional
interactions is calculated in the impact regime by using the
quantum-fluctuation-regression theorem. Various interesting effects are
found. For example, the scattered intensity spectrum for a J = 0 to
J = 1 transition for polarization parallel to the laser polarization
is essentially an asymmetric triplet, whereas for a perpendicular
polarization due to collisions the spectrum is essentially a doublet
(whose frequencies do not correspond with any of those of the
triplet). Further, the width of the fluorescent component (whose
frequency is close to the unperturbed frequency) actually decreases
with increasing laser power.
Title: Resonance fluorescence in a weak radiation field with arbitrary
spectral distribution
Authors: Raymer, M. G.; Cooper, J.
Bibcode: 1979PhRvA..20.2238R
Altcode:
The authors show that the laser bandwidth effects in resonance
fluorescence at low intensities can be treated most readily in terms
of simple convolutions, and further that this approach allows one to
consider an incident field with an arbitrary spectral distribution,
with or without the presence of atomic (line-broadening) collisions.
Title: Redistribution Theory of Lyman β Radiation
Authors: Rousseldupre, D. C.; Cooper, J.; Ballagh, R. J.
Bibcode: 1979BAAS...11..411R
Altcode:
No abstract at ADS
Title: Redistribution of scattered radiation by collisions in the
nonimpact region of the spectral line profile.
Authors: Cooper, J.
Bibcode: 1979ApJ...228..339C
Altcode:
The scattering of radiation in the presence of collisions can
be described quantum-mechanically in terms of essentially two
processes. The first may be thought of as an absorption to the excited
state followed subsequently (after propagating in the excited state)
by emission. This gives rise to radiation redistributed about the
transition frequency. The effects of m-degeneracy are particularly
interesting for this first process. As an example a case is considered
in which the incident frequency is in the quasi-static line wing, while
the scattered frequency is close to the line center. It is found that
under these circumstances the dominant contribution from this process
in the scattered spectrum is obtained for an absorption of the incident
frequency taking place during a strong (close) collision and reemission
of the scattered frequency when the atom is essentially unperturbed
Title: Stark broadening of Fe I 5383 Å.
Authors: Freudenstein, S.; Cooper, J.
Bibcode: 1979A&A....71..283F
Altcode:
Results are reported for a laboratory measurement of the electron
broadening of the Fe I line at 5383 A as a function of electron
density over the temperature range from 8000 to 12,000 K. A linear
Z-pinch electrical discharge served as the spectroscopic light source
in the experiment, and special precautions were taken to allow for
optical-depth effects, which have been a major source of error in
previous investigations. The results obtained include a Stark-broadening
constant of 0.106 + or - 0.004 x 10 to the -16th A-cu cm at a mean
temperature of 9500 K, an estimated Stark width/electron-broadened
width ratio of 1.09 + or - 0.02, and a normalized electron-broadened
width of 0.097 + or - 0.004 x 10 to the 16th A-cu cm. Comparison of the
last result with a calculated value and with a previous measurement
indicates that the present measurement is approximately 38% larger
than the value measured earlier.
Title: A simple formula for estimating Stark widths of neutral lines.
Authors: Freudenstein, S. A.; Cooper, J.
Bibcode: 1978ApJ...224.1079F
Altcode:
A simple formula for the prediction of Stark widths of neutral lines
similar to the semiempirical method of Griem (1968) for ion lines is
presented. This formula is a simplification of the quantum-mechanical
classical path impact theory and can be used for complicated atoms for
which detailed calculations are not readily available, provided that
the effective position of the closest interacting level is known. The
expression does not require the use of a computer. The formula has
been applied to a limited number of neutral lines of interest, and the
width obtained is compared with the much more complete calculations of
Bennett and Griem (1971). The agreement generally is well within 50%
of the published value for the lines investigated. Comparisons with
other formulas are also made. In addition, a simple estimate for the
ion-broadening parameter is given.
Title: Role of collisional repopulation of atomic levels on coherent
and redistributed components in resonant light scattering
Authors: Cooper, J.; Ballagh, R. J.
Bibcode: 1978PhRvA..18.1302C
Altcode:
Resonant scattering (redistribution) of weak monochromatic light by
atoms in the presence of collisions has been considered by Omont et
al., who allowed for the broadening of both upper and lower levels
of the transition. Mollow (who also has considered this problem for
intense radiation) has shown that their results are applicable only
if collisional repopulation of the levels (in contrast to collisional
depopulation) is ignored. We here consider in detail the effect of
repopulation. It leads, in the weak-field limit, to a true-coherent
component (δ-function spectrum) at the driving frequency, as well as a
component at this frequency whose width is essentially the inelastic
collisional rate of the lower state. An additional redistributed
component due to repopulation of the upper level is also obtained.
Title: The angular dependence of partially redistributed resonance
radiation.
Authors: Ballagh, R. J.; Cooper, J.
Bibcode: 1977ApJ...213..479B
Altcode:
Explicit expressions for the angular distribution and frequency
dependence of radiation scattered by a spatially degenerate atom
undergoing collisions are derived using a previously developed
formalism of the quantum theory of line broadening for an atom
in its rest frame. Results valid in the impact regime for resonant
scattering are presented for the cases of linear incident and scattered
polarization circular incident and linear scattered polarization,
and unpolarized incident radiation with no monitoring of the scattered
polarization. These results relate to scattering involving a j - j +
or - 1 - j atomic transition, with lower-state interactions neglected;
the expressions obtained take a relatively simple form involving atomic
multipolar relaxation rates of the order of k = 0 and k = 2. The
angular distributions for each case are combined with the frequency
dependences to yield a three-component frequency redistribution
function for an s-p-s transition, the components being a coherent term,
a frequency-redistributed term with the same angular dependence as
the coherent term, and an isotropic frequency-redistributed term.
Title: A shock tube study of line broadening in a temperature range
of 6100 to 8300 K.
Authors: Baur, J. F.; Cooper, J.
Bibcode: 1977JQSRT..17..311B
Altcode:
Line widths of the Ca(II) 3968 A and Na(I) 5890 A resonance lines
broadened by electric microfields in a plasma were measured. A
pressure-driven shock tube was used as the light source. Radiation
from the equilibrium region behind the reflected shock wave was studied
using a rapid scanning Fabry-Perot interferometer. Electron and argon
atom densities of about 8 x 10 to the 16th and 1 x 10 to the 19th/cu cm,
respectively, were achieved at the relatively low temperature of around
7500 K by vaporizing a cesium powder that had been added to the shock
tube as a solid aerosol in argon gas. The measured line widths were
predominantly Stark broadened by the electrons and ions in the plasma,
although Doppler, van der Waals, instrument function and optical depth
effects had to be taken into account.
Title: Correlations between Doppler and pressure broadening for the
resonance interaction
Authors: Cooper, J.; Stacey, D. N.
Bibcode: 1975PhRvA..12.2438C
Altcode:
The correlation between Doppler and collisional broadening has been
considered in detail for radiation in which the lower level of the
transition is broadened by the resonance interaction. It is found
that rather than a single Voigt profile, the profile of the radiation
is essentially a sum of Voigt profiles. Although the widths of these
profiles vary by some 40%, the over-all line shape is very close to
the single Voigt shape obtained when correlation effects are neglected.
Title: H - shape-resonance studies in an arc plasma
Authors: Ott, W. R.; Slater, J.; Cooper, J.; Gieres, G.
Bibcode: 1975PhRvA..12.2009O
Altcode:
Calculations by Macek have shown that the H-
photoabsorption cross section should be affected by a shape
resonance at 1129.5 Å. This experiment is an attempt to
observe the resonance in emission according to the reaction
e+H-->[H-]*-->H-+hν. The plasma
is in a condition of local thermodynamic equilibrium and is generated
by a stationary wall-stabilized hydrogen arc. With an axis temperature
of 14000 K and 1 atm pressure, the H- free-bound continuum
contributes only about 2% of the total radiation which is dominated in
the 1130-Å region by the Ly-α wing. However, the peak of the shape
resonance, according to Macek, should have a cross section about 25
times greater than the continuous free-bound cross section; therefore,
it should appear as a very noticeable 50% structure superimposed on
the Ly-α wing. Except for some small features which are attributed to
weak molecular emission, there is no obvious indication of the shape
resonance in either deuterium or hydrogen spectra between 1105 and
1135 Å. It is estimated that the minimum feature which could have
been detected at 1129 Å was about 2% of the total signal.
Title: On the effect of time-ordering for Lyman-alpha .
Authors: Greene, R. L.; Cooper, J.
Bibcode: 1975JQSRT..15..991G
Altcode:
Numerical calculations of the wings of the hydrogen Lyman-alpha line
due to Stark broadening by electrons have been performed including time
ordering effects. It is concluded that two recent calculations, which
apparently disagree, are numerically correct within their respective
approximations and their differences are explained.
Title: A unified theory of Stark broadening for hydrogenic ions-I. A
general theory (including time ordering).
Authors: Greene, R. L.; Cooper, J.; Smith, E. W.
Bibcode: 1975JQSRT..15.1025G
Altcode:
No abstract at ADS
Title: Stark broadening tables for He I lambda 4922 Å.
Authors: Barnard, A. J.; Cooper, J.; Smith, E. W.
Bibcode: 1975JQSRT..15..429B
Altcode:
The Stark broadening of the He I 4922-A line and its forbidden
components by both ions and electrons is calculated using a theory that
includes ion dynamic effects. Tables are presented for temperatures
from 5000 K to 40,000 K covering the density range 10 trillion to 10
quadrillion per cu cm for both helium and hydrogen ionic perturbers.-
Title: He I lambda 4922 profiles in B stars: calculations with an
improved line broadening theory.
Authors: Mihalas, D.; Barnard, A. J.; Cooper, J.; Smith, E. W.
Bibcode: 1975ApJ...197..139M
Altcode:
Theoretical profiles for the He I A4922 line in B star spectra have
been computed using the improved broadening theory of Barnard, Cooper,
and Smith, and the level populations calculated by Auer and Mihalas
from a simultaneous self-consistent solution of the coupled transfer
and statistical equilibrium equations. The revised broadening theory
yields excellent agreement with laboratory measurements of the width
and intensity of the forbidden (2p ) transition. The results of this
paper show that stellar profiles computed with the new theory are
in excellent agreement with observed profiles, and the discrepancies
between observation and theory that existed previously have now been
removed. Subject headings: early-type stars - line profiles
Title: A unified theory of Stark broadening for hydrogenic
ions-II. Line wings.
Authors: Greene, R. L.; Cooper, J.
Bibcode: 1975JQSRT..15.1037G
Altcode:
No abstract at ADS
Title: A unified theory of Stark broadening for hydrogenic
ions-III. Results for He II Lyman-alpha .
Authors: Greene, R. L.; Cooper, J.
Bibcode: 1975JQSRT..15.1045G
Altcode:
No abstract at ADS
Title: He I lambda 4471 profiles in B stars: calculation with an
improved line-broadening theory.
Authors: Mihalas, D.; Barnard, A. J.; Cooper, J.; Smith, E. W.
Bibcode: 1974ApJ...190..315M
Altcode:
Theoretical profiles for the He I A4471 line in B-star spectra
have been computed using an improved broadening theory of Barnard,
Cooper, and Smith, together with level populations determined by a
self-consistent solution by Auer and Mihalas of the coupled transfer
and statistical-equilibrium equations. The broadening theory has been
constructed to provide a more accurate description of the intensity
and width of the forbidden (2p 3P0-4f 3F ) transition as measured
in laboratory experiments. The results presented in this paper show
that this revision of the broadening theory leads to computed stellar
profiles which are in much better agreement with observed profiles
than any previously obtained. Subject headings: early-type stars -
line profiles
Title: Correlation effects in the theory of combined Doppler and
pressure broadening - I. Classical theory.
Authors: Ward, J.; Cooper, J.; Smith, E. W.
Bibcode: 1974JQSRT..14..555W
Altcode:
No abstract at ADS
Title: The broadening of He I lines including ion dynamic corrections,
with application to lambda 4471 Å.
Authors: Barnard, A. J.; Cooper, J.; Smith, E. W.
Bibcode: 1974JQSRT..14.1025B
Altcode:
No abstract at ADS
Title: Redistribution of Resonance Radiation. 11. the Effect of
Magnetic Fields
Authors: Omont, A.; Smith, E. W.; Cooper, J.
Bibcode: 1973ApJ...182..283O
Altcode:
Previously obtained results for scattering of radiation in the presence
of collisions are restated in a density matrix formalism which employs
an irreducible-tensor description of the radiation field. This formalism
is particularly useful for problems associated with radiative transfer
theory. The redistribution is then extended to include the effect of
a weak magnetic field. By averaging over a finite bandwidth which is
on the order of the Doppler width, simplified expressions of physical
significance for the scattering in the Doppler core and the Lorentz
wings are obtained. Expressions are also obtained for the corresponding
source function of radiative transfer theory. Subject headings:
magnetic fields - polarization - radiative transfer
Title: Satellites to LYMAN-a due to Protons
Authors: Stewart, J. C.; Peek, J. M.; Cooper, J.
Bibcode: 1973ApJ...179..983S
Altcode:
Line broadening of the wings of La is calculated by using accurate H2 +
wave functions. Of particular interest are the linelike satellites which
appear prominently at 1233.5, 1240.5, and 1404.9 A. Subject headings:
line formation - line profiles - spectra, ultraviolet
Title: An analysis of the unified and scalar additivity theories of
spectral line broadening.
Authors: Smith, E. W.; Cooper, J.; Roszman, L. J.
Bibcode: 1973JQSRT..13.1523S
Altcode:
No abstract at ADS
Title: Hydrogen Stark-Broadening Tables
Authors: Vidal, C. R.; Cooper, J.; Smith, E. W.
Bibcode: 1973ApJS...25...37V
Altcode:
Tables of Stark broadening of the first four Lyman lines and the
first four Balmer lines of hydrogen are presented. They are based on a
recently developed "unified theory" of line broadening which generates
normalized profiles covering the entire profile from the impact limit
in the line center to the quasi-static limit in the line wings. The
tables are presented in a convenient form for accurate numerical
interpolation. Subject heading: line profiles
Title: Redistribution of Resonance Radiation. I. The Effect of
Collisions
Authors: Omont, A.; Smith, E. W.; Cooper, J.
Bibcode: 1972ApJ...175..185O
Altcode:
The techniques of modern line-broadening theory are used to investigate
the scattering of polarized radiation in the rest frame of an atom
undergoing collisions. The formulation explicitly includes both elastic
and inelastic (quenching) collisions. When the lower state has zero
width, a form for the redistribution function similar to that of Zanstra
is obtained, but with the redistribution in the neighborhood of the
resonance line being caused solely by elastic collisions. In the limit
of no collisions, but with both levels of finite lifetime, the result
of `veisskopf and Woolley is obtained. The effect of level-degeneracy
is also explicitly included; in this case the results are a function
of the polarization of the light and the different relaxation rates
for the multipolar components of the atomic states.
Title: Overlap of Argon Ion Spectra with Satellites to the Lyman-Alpha
Lines of Carbon and Boron
Authors: Jalufka, N. W.; Cooper, J.
Bibcode: 1972ApJ...171..647J
Altcode:
A theta pinch has been employed to investigate satellites to the H-like
and He-like ion resonance lines of boron and carbon. Identification
of the spectra shows an overlap of the Ar ix, Ar xi, and Ar xii lines
with the predicted satellite wavelengths, and it is concluded that many
of the previously reported satellite lines are due to argon impurities.
Title: Determination of Van der Waals broadening at temperatures of
astrophysical interest.
Authors: Cooper, J.; Evans, J. M., Jr.
Bibcode: 1972JQSRT..12..259C
Altcode:
No abstract at ADS
Title: An impact theory for Doppler and pressure broadening -
I. General theory.
Authors: Smith, E. W.; Cooper, J.; Chappell, W. R.; Dillon, T.
Bibcode: 1971JQSRT..11.1547S
Altcode:
No abstract at ADS
Title: An impact theory for Doppler and pressure broadening -
II. Atomic and molecular systems.
Authors: Smith, E. W.; Cooper, J.; Chappell, W. R.; Dillon, T.
Bibcode: 1971JQSRT..11.1567S
Altcode:
No abstract at ADS
Title: Non-adiabatic effects in Van der Waals broadening.
Authors: Stacey, D. N.; Cooper, J.
Bibcode: 1971JQSRT..11.1271S
Altcode:
No abstract at ADS
Title: Unified theory calculations of Stark broadened hydrogen lines
including lower state interactions.
Authors: Vidal, C. R.; Cooper, J.; Smith, E. W.
Bibcode: 1971JQSRT..11..263V
Altcode:
No abstract at ADS
Title: Hydrogen Stark broadening calculations with the unified
classical path theory.
Authors: Vidal, C. R.; Cooper, J.; Smith, E. W.
Bibcode: 1970hsbc.book.....V
Altcode:
No abstract at ADS
Title: Computed profiles of He I 5016 Å at high electron densities.
Authors: Barnard, A. J.; Cooper, J.
Bibcode: 1970JQSRT..10..695B
Altcode:
Profiles of He I 5016Åand its forbidden component have been calculated
and are tabulated for electron densities from 3×1016
to 6×1017 cm-3 and temperatures from
104 to 8×104°K. The ion broadening is treated
in the quasistatic approximation and the electron broadening of the
overlapping Stark components in the impact approximation. The effect
of the broadening of the lower level by electrons has been taken into
account, and intermediate states up to n = 6 have been included.
Title: Non-thermal effects in Stark broadening.
Authors: Chappell, W. R.; Cooper, J.; Smith, E. W.
Bibcode: 1970JQSRT..10.1195C
Altcode:
No abstract at ADS
Title: Hydrogen Stark broadening calculations with the unified
classical path theory
Authors: Vidal, C. R.; Cooper, J.; Smith, E. W.
Bibcode: 1970JQSRT..10.1011V
Altcode:
The unified theory has been generalized for the case of upper
and lower state interaction by introducing a more compact tetradic
notation. The general result is then applied to the Stark broadening
of hydrogen. The thermal average of the time development operator for
upper and lower state interaction is presented. Except for the time
ordering it contains the effect of finite interaction time between
the radiator and perturbers to all orders, thus avoiding a Lewis type
cutoff. A simple technique for evaluating the Fourier transform of
the thermal average has been developed. The final calculations based
on the unified theory and on the one-electron theory are compared with
measurements in the high and low electron density regime. The unified
theory calculations cover the entire line profile from the line center
to the static wing and the simpler one-electron theory calculations
provide the line intensities only in the line wings.
Title: Unified Classical-Path Treatment of Stark Broadening in Plasmas
Authors: Smith, Earl W.; Cooper, J.; Vidal, C. R.
Bibcode: 1969PhRv..185..140S
Altcode:
A theoretical treatment of spectral line broadening in plasmas is
developed using classical-path methods. This treatment unifies certain
aspects of the familiar impact, one-electron, and relaxation theories
to produce results which are valid from the line center to the far line
wings where the electrons may behave quasistatically. Calculations of
the Lyman-α line of hydrogen are used to illustrate the theory.
Title: Electron-Impact Broadening of Isolated Lines of Neutral Atoms
in a Plasma. I
Authors: Cooper, J.; Oertel, G. K.
Bibcode: 1969PhRv..180..286C
Altcode:
This paper deals with the generalized impact theory for electron
broadening of isolated spectral lines emitted by neutral atoms in a
plasma. The existing theory is improved by quantitative evaluation of
the second-order (quadrupole) term in the multipole expansion including
broadening of the lower level and interference effects, by approximate
inclusion of the "back reaction" of atom on perturber in inelastic
collisions through symmetrization with respect to initial and final
perturber states, and by corrections to the broadening functions in
the classical-path approximation. While the quadrupole contribution is
normally a small correction, it is shown that it may, in principle,
dominate the weak collision broadening in some situations even when
the multipole series converges; however, strong collisions will always
dominate in this case. Numerical results of the improved theory are
given for the half-widths at half-maximum of some helium i lines,
and the effects of the corrections are evaluated.
Title: Electron correlations in Stark broadening.
Authors: Chappell, W. R.; Cooper, J.; Smith, E. W.
Bibcode: 1969JQSRT...9..149C
Altcode:
No abstract at ADS
Title: On Strong Collisions in Hydrogenic Line Broadening
Authors: Shen, K. Y.; Cooper, J.
Bibcode: 1969ApJ...155...37S
Altcode:
The degeneracy of hydrogenic states is used to sum approximately
the S-matrix to all orders in Stark- broadening calculations. It is
found that the usual strong-collision cutoff for lower lines should
represent a reasonable approximation. However, there could be a
significant difference between our results and previous calculations
for transitions among levels with large principal quantum numbers
Title: 10. The Broadening of He I 4471 A and its Forbidden Components
Authors: Barnard, A. J.; Cooper, J.; Shamey, L. J.
Bibcode: 1969LIACo..15...89B
Altcode: 1969MSRSL..17...89B
No abstract at ADS
Title: Stark broadening of the Na I 5682 - 88 A and 4978 - 82 A lines.
Authors: Oettinger, P. E.; Cooper, J.
Bibcode: 1969JQSRT...9..591O
Altcode:
No abstract at ADS
Title: Calculated Profiles of He I 4471 and 4922 A and their Forbidden
Components
Authors: Barnard, A. J.; Cooper, J.; Shamey, L. J.
Bibcode: 1969A&A.....1...28B
Altcode:
The proffles of He 14471 and 4922 A and their forbidden components have
been calculated and are tabulated for electron densities in the range
1014 to 1017 cm-8, and for temperatures from 5000 to 40000 0K. The
ion broadening is treated in the quasistatic approximation and the
electron broadening of the overlapping Stark components in the impact
approximation. Stark parameters are also tabulated from which proffles
may be obtained for densities below 10^14 cm-8.
Title: The broadening of He I 4471 Å and its forbidden components.
Authors: Barnard, A. J.; Cooper, J.; Shamey, L. J.
Bibcode: 1969MSRSL..25...89B
Altcode: 1969tisa.conf...89B
No abstract at ADS
Title: Plasma spectroscopy
Authors: Cooper, J.
Bibcode: 1966RPPh...29...35C
Altcode:
No abstract at ADS