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Two photon physics at RHIC

Description: Because the two photon cross section is proportional to Z{sup 4}, heavy ion colliders offer an unmatched luminosity. However, because nuclei have finite sizes, the photon spectrum is gradually cut off by a nuclear form factor. For RHIC, this cutoff occurs at a few GeV; below this energy, RHIC will have the highest {gamma}{gamma} luminosity in the world when it turns on. In addition to the high rates, because Z{alpha} {approximately} 0.6, the nuclear environment provides a window to strong field QED and new phenomena like multiple pair production. To study {gamma}{gamma} physics, regions where the nuclei interact hadronically must be avoided; this leads to roughly a factor of two loss in usable luminosity. The rates expected by the Solenoidal Tracker at RHIC (STAR) collaboration will be given. Backgrounds will be discussed, along with several rejection techniques.
Date: May 1, 1995
Creator: Klein, S.
Partner: UNT Libraries Government Documents Department

Polynomial solutions of the Schroedinger equation applied to photon cross sections in atoms

Description: Solutions of the Schrodinger equation with a realistic potential are carried out in detail. To check the methods, a few boundbound, bound-free, and free-free cross sections were calculated and values compared with existing calculations and experimental data. These comparisons, along with a listing of the computer code in its bound-free form, are included. (auth)
Date: August 1, 1973
Creator: Merts, A.L. & Matuska, W. Jr.
Partner: UNT Libraries Government Documents Department

EPDL97: the evaluated photo data library `97 version

Description: The Evaluated Photon Data Library, 1997 version (EPLD97), is designed for use in photon transport calculations at Lawrence Livermore National Laboratory. This library includes photon interaction data for all elements with atomic number between Z = 1 (hydrogne) and 100 (fermium), including: photoionization, photoexcitation, coherent and incoherent scattering, and pair and triplet porduction cross sections. For use in applications data is provided for all elements over the energy range 1 eV to 100 GeV. This report documents the sources and treatment of the data included inthis library. EPDL97 completely supersedes the earlier 1989 version of EPDL and it is highly recommended that useres only use the most recent version of this library.
Date: September 19, 1997
Creator: Cullen, D.E.; Hubbell, J.H. & Kissel, L.
Partner: UNT Libraries Government Documents Department

Multiple scattering enhancement of x rays

Description: A Monte Carlo calculation is described for the determination of the contribution of multiple scattering to x rays scattered at 90 deg in various thicknesses of beryllium and carbon plates. The plates are inclined at an angle of 45 deg to the incident radiation. The photon energy range considered is 1 keV to 100 keV. Scatterer thicknesses range from 0.0046 g/cm/sup 2/ to 1.204 g/ cm/sup 2/. Two sets of results are given: one from a formulation neglecting the polarization, the other including polarization. Results are presented in the form of an enhancement factor defined as the ratio of the number of scattered photons escaping from the scatterer at 90 deg to the number escaping at 90 deg after scattering only once. Enhancement factors are given in both tabular and graphical form. (auth)
Date: February 1, 1974
Creator: Bennett, E.W.
Partner: UNT Libraries Government Documents Department

Photon Linear Collider Gamma-Gamma Summary

Description: High energy photon - photon collisions can be achieved by adding high average power short-pulse lasers to the Linear Collider, enabling an expanded physics program for the facility. The technology required to realize a photon linear collider continues to mature. Compton back-scattering technology is being developed around the world for low energy light source applications and high average power lasers are being developed for Inertial Confinement Fusion.
Date: February 27, 2012
Creator: Gronberg, J
Partner: UNT Libraries Government Documents Department

Correlation holography: imaging of atoms when sigma/sub inelastic//sup >>sigma/elastic

Description: Atomic-scale resolution of details is possible with this method, even if protons interact with the atoms overwhelmingly inelastically, i.e. when sigma/sub inelastic/ >>sigma/sub elastic/. Observation of small objects is compatible with quantum mechanics even if the disturbance of the object caused by the observation process is arbitrarily small.
Date: January 1, 1979
Creator: Csonka, P.L.
Partner: UNT Libraries Government Documents Department

Polariton effects in naphthalene crystals

Description: The experimental verification of the two-step nature of energy dissipation of photon energy by a crystal is the subject of this dissertation. The ..cap alpha..(O,O) Davydov component of the lowest energy singlet transition in pure strain-free napthalene single crystals is shown to exhibit an increase in absorption with increasing temperature, due to an increase in polariton damping via polariton-phonon scattering processes. (GHT)
Date: October 1, 1977
Creator: Robinette, S. L.
Partner: UNT Libraries Government Documents Department

The structure of the stable negative ion of calcium

Description: The structure of the Ca/sup /minus// ion has been determined using a crossed laser-ion beams apparatus. The photoelectron detachment spectrum shows that, contrary to earlier expectations, the Ca/sup /minus// ion is stably bound in the (4s/sup 2/4p)/sup 2/p state. The electron affinity of Ca was measured to be 0.043 /sup + -/ 0.007 eV.
Date: January 1, 1988
Creator: Pegg, D.J.; Thompson, J.S.; Compton, R.N. & Alton, G.D.
Partner: UNT Libraries Government Documents Department

Negative-ion states

Description: In this brief review, we discuss some of the properties of atomic and molecular negative ions and their excited states. Experiments involving photon reactions with negative ions and polar dissociation are summarized. 116 references, 14 figures.
Date: January 1, 1982
Creator: Compton, R.N.
Partner: UNT Libraries Government Documents Department

Fluorescent scattering by molecules embedded in small particles. Progress report, February 1, 1981-January 31, 1982

Description: In earlier work a model of fluorescent and Raman scattering by active molecules represented as classical electric dipoles embedded in small particles was developed. The intensity and angular distribution of the inelastically scattered radiation was shown to depend on the geometric and optical properties of the particle. The model was originally developed for particles having spherical shape and later extended to concentric spheres, cylinders, and prolate spheroids. The active molecules were originally assumed to be isotropically polarizable. The model has been recently extended to certain types of anisotropically polarizable molecules. The model had also been applied to particles having internal structure.
Date: January 31, 1982
Creator: Chew, H. & McNulty, P.J.
Partner: UNT Libraries Government Documents Department

Photon damping in cosmic-ray acceleration in active galactic nuclei

Description: The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.
Date: April 7, 1983
Creator: Colgate, S.A.
Partner: UNT Libraries Government Documents Department

Multiphoton processes: conference proceedings

Description: The chapters of this volume represent the invited papers delivered at the conference. They are arranged according to thermatic proximity beginning with atoms and continuing with molecules and surfaces. Section headings include multiphoton processes in atoms, field fluctuations and collisions in multiphoton process, and multiphoton processes in molecules and surfaces. Abstracts of individual items from the conference were prepared separately for the data base. (GHT)
Date: January 1, 1984
Creator: Lambropoulos, P. & Smith, S.J. (eds.)
Partner: UNT Libraries Government Documents Department

Applications of resonance ionization spectroscopy to ultralow-level counting and mass spectroscopy

Description: The ability to directly detect a daughter atom, using resonance ionization spectroscopy, in delayed time coincidence with the decay of a parent species promises to drastically reduce the background in low-level counting experiments. Resonance ionization can also be used as an ion source for a mass spectrometer system that is capable of discriminating between isobars.
Date: January 1, 1979
Creator: Kramer, S.D.; Hurst, G.S.; Young, J.P.; Payne, M.G.; Kopp, M.K.; Callcott, T.A. et al.
Partner: UNT Libraries Government Documents Department

Photodetachment collisions

Description: A crossed-beams apparatus has been used to measure the cross sections (angular differential and integral) for photodetaching electrons from metastable He/sup/minus// and stable B/sup/minus// ions at /lambda/ = 696.2 nm. Kinematic effects were exploited, in a novel way, to enhance the precision of the measurements. The partial (angular integral) cross sections for He/sup /minus// photodetachment are /sigma/(2/sup 3/S) = 22.9 /plus minus/ 1.0 Mb and /sigma/(2/sup 3/P) = 10.0 /plus minus/ 0.6 Mb. The corresponding cross section for B/sup/minus// is /sigma/(2 /sup 2/) = 16.5 /plus minus/ 2.1 Mb. The calculated cross section for the photodetachment of D/sup /minus// was used to establish an absolute scale for the relative measurements. Radiative attachment cross sections are derived from the photodetachment results using the principle of detailed balance. 16 refs., 9 figs., 2 tabs.
Date: January 1, 1989
Creator: Pegg, D.J.
Partner: UNT Libraries Government Documents Department

Characterization of multiple-photon absorption and dissociation of polyatomic molecules

Description: A quantitative comparison of multiple-photon absorption (MPA) and dissociation (MPD) has been performed for experiments with a number of different polyatomic molecules. Appropriate normalization techniques for the absorption and dissociation parameters are formulated to account for the different conditions of the experiment and the molecular parameters. This procedure in a first approximation, accounts for the effects of independent variables such as gas pressure, optical bandwidth, optical pulse duration, excitation frequency, spectral width of the optical absorption band, absorption strength of the transition, bond strength, and the density of states in the molecule. The theoretical description of the dynamics of the absorbing ground state is considered and used to provide the rationale for the normalization procedure. The results of this analysis indicate that the functional dependence of the number of photons absorbed per molecule with fluence is qualitatively the same for the most molecules. Similarly, the probability for dissociation of most molecules can be related to the density of vibrational states, the bond strength, the number of photons absorbed per molecule, and the width of the absorbing transition. The functional relationships derived for MPA and MPD can be related to several theoretical aspects of the optical interaction process. In particular, the implications for the basic absorption mechanisms and the distribution of vibrational energy in the molecule will be addressed.
Date: January 1, 1980
Creator: Judd, O.P.
Partner: UNT Libraries Government Documents Department

Inverse bremsstrahlung absorption rate in an intense laser field

Description: Inverse bremsstrahlung is one of the important mechanisms for transferring energy from laser light to matter. The computer code LASNEX currently uses a simple physical model for this process for which there can be substantial corrections. The purpose of this investigation is to provide a model for the bremsstrahlung process that will be applicable over the whole range of interest for use in LASNEX. The derivation of the bremsstrahlung cross section and various approximate forms useful in the numerical calculations, and derivation of the expression for the energy absorption rate for a general distribution function and special forms for various approximations to the cross section are presented. The alternative methods of derivation of the energy absorption rate are discussed. Numerical results are presented along with comparison among the different expressions, and the validity of the assumptions and methods to relax the approximations are discussed.
Date: November 1, 1978
Creator: Schlessinger, L. & Wright, J.
Partner: UNT Libraries Government Documents Department

Quenching of Einstein-coefficients by photons

Description: Experimental evidence is presented for the change of Einstein's A- coefficients for spontaneous transitions from the upper laser level of argon ion laser discharge due to the presence of the high- intensity laser flux. To demonstrate that this quenching effect cannot be attributed to a reduction in self-absorption of the strong spontaneous emission line, absorption and line profile measurements have been performed. Computer modelling of the reduction of self absorption due to Rabi splitting also indicated that this effect is too small to explain the observed quenching of spontaneous line emissions. 13 refs., 11 figs.
Date: March 1, 1991
Creator: Aumayr, F. (Technische Univ., Vienna (Austria). Inst. fuer Allgemeine Physik); Lee, W.; Skinner, C.H. & Suckewer, S. (Princeton Univ., NJ (USA). Plasma Physics Lab.)
Partner: UNT Libraries Government Documents Department

1985 bibliography of atomic and molecular processes

Description: This annotated bibliography includes papers on atomic and molecular processes published during 1985. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.
Date: June 1, 1986
Creator: Barnett, C.F.; Gilbody, H.B.; Gregory, D.C.; Griffin, P.M.; Havener, C.C.; Howald, A.M. et al.
Partner: UNT Libraries Government Documents Department

Quantitative comparison of multiple-photon absorption in polyatomic molecules

Description: A quantitative comparison of multiple-photon absorption for a number of polyatomic molecules has been performed. A basis for this comparison has been developed that takes into account the different experimental conditions and molecular parameters, and provides suitable normalization of the fluence and absorption parameters. The normalization, and consequently the generalized interaction process can be specified in terms of the spectroscopic absorption cross section of the molecule sigma/sub 0/(..nu..) and the effective fraction of molecules that interact with the radiation field <f>. The results of the study indicate that in terms of the normalized absorption variables, multiple-photon absorption is a general phenomena that is qualitatively the same for all molecules; quantitative differences can be related to differences in sigma/sub 0/ and <f>. The absorption of all polyatomic molecules can be described in terms of the number of photons absorbed per molecule eta(PHI) at a fluence PHI. The data indicate that in spectral regions where sigma/sub 0/(..nu..) greater than or equal to 0.1 sigma/sub 0/ (max), eta(PHI) can be represented by the function PHI/sup ..gamma../ where ..gamma.. = 1 for sigma/sub 0/PHI/<f> < 1 and ..gamma.. approx. = 2/3 for sigma PHI/<f> > 1. Quantitative values of <f> and the functional dependence of eta(PHI) on the experimental parameters such as gas pressure, optical bandwidth, and optical pulse duration are derived and shown to be in good agreement with experimental data for SF/sub 6/. These results are also compared with the anharmonic oscillator model for multiple-photon excitation of polyatomic molecules.
Date: January 1, 1979
Creator: Judd, O. P.
Partner: UNT Libraries Government Documents Department