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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

Molecular Photoionization Dynamics

Description: This program seeks to develop both physical insight and quantitative characterization of molecular photoionization processes. Progress is briefly described, and some publications resulting from the research are listed. (WHK)
Date: January 1, 1982
Creator: Dehmer, J. L.
Partner: UNT Libraries Government Documents Department

Laser-material interactions: A study of laser energy coupling with solids

Description: This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding.
Date: November 1, 1993
Creator: Shannon, M. A.
Partner: UNT Libraries Government Documents Department

Investigation of synchrotron radiation-induced photodesorption in cryosorbing quasi-cooled geometry. Revision 2

Description: We report 4.2-K photodesorption experiments in two quasi -- closed geometries-a simple tube and a tube with a coaxial perforated liner -- designed to manure separately the desorption coefficients of tightly bound and physisorbed molecules. The results are important for the beam tube vacuum of the next generation of superconducting proton colliders that have been contemplated-the 20-TeV Superconducting Super Collider (SSC) in the United States and the 7.3-TeV Large Hadron Collider (LHC) at CERN.
Date: April 1, 1994
Creator: Anashin, V. V.; Malyshev, O. B.; Osipov, V. N.; Maslennikov, I. L. & Turner, W. C.
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

Atomic scale resolution with correlation holography

Description: For many atoms (including atoms of interest in biology) the elastic and inelastic photon scattering cross sections (denoted respectively by sigma/sub el/ and sigma/sub inel/) for photons in the wavelength region of interest, satisfy sigma/sub el/ << sigma/sub inel/. Therefore, the probability is high that when illuminated with photons, such an atom will decay before a holographic picture of it can be taken. On the other hand, if certain nonlinear phenomena: correlations between photons are taken into account, a hologram of such atoms can nevertheless be generated. Observation of small objects is compatible with the principles of quantum mechanics, even if the probability of disturbing the object as a result of observation 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

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

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

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

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 &lt;f&gt;. 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 &lt;f&gt;. 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/&lt;f&gt; &lt; 1 and ..gamma.. approx. = 2/3 for sigma PHI/&lt;f&gt; &gt; 1. Quantitative values of &lt;f&gt; 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

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