Author name code: cooper ADS astronomy entries on 2022-09-14 =author:"Cooper, J." year:1965-1995 ------------------------------------------------------------------------ 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