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Supernova type I luminosity

Description: The full time-dependent radiation spectrum of a supernova starts when the explosion shock wave reaches the surface of the presupernova envelope. An early radiation spectrum emitted by the expanded and cooling shock-ejected outer layers of an initially compact (R = 10/sup 8/ cm) type I supernova is derived. The relativistically ejected matter is presumably cosmic rays. The Doppler shifted and relativistically time contracted Planck radiation emitted from the expanding surface layers results in an emitted radiation associated with the cooling corresponding to an energy flux of 1.3 x 10/sup 43/ t/sup -1/./sup 05/ ergs sec/sup -1/ with a spectrum I(h..nu..) dh..nu.. = 1.5 x 10/sup 43/ (h..nu..)/sup -0/./sup 92/ ergs eV/sup -1/ and time behavior (h..nu..)/sub eff/ = 108 t/sup -0/./sup 61/ eV. The optical luminosity from the shock is thus low congruent to 10/sup 40/ ergs sec/sup -1/ and 10/sup 43/ ergs total so that it would not be seen as a precursor to the main optical outburst occurring several days later. The x-ray luminosity (several x 10/sup 43/ ergs in milliseconds) is observable but small compared to extended envelope models. The later optical light curve is then interpreted in terms of radioactive heating, ionization and excitation by 0.2 M/sub solar/ of /sup 56/Ni decaying via /sup 56/Co to /sup 56/Fe. Van Hise (1974) has already pointed out that the two optical decay constants are closely given by the respective radioactive decay constants multiplied by 3/4. This is interpreted as requiring efficiency to produce optical radiation, the Fe/sup +/blend, proportional to the (decay rate)/sup 1/3/. It is further noted that when the two optical decay rates are extrapolated to zero time, the intercepts agree with the predicted ratio of deposited energy from /sup 56/Ni ..-->.. /sup 56/Co, and from /sup 56/Co ..-->.. /sup 56/Fe when the appropriate fractional absorption ...
Date: January 1, 1978
Creator: Colgate, S.A. & Petschek, A.
Partner: UNT Libraries Government Documents Department

Charged hadron production in e/sup +/e/sup -/ annihilation at. sqrt. s = 29 GeV

Description: Data from the Time Projection Chamber at the SLAC storage ring PEP have been used to study the inclusive production of charged hadrons. Particles were identified by simultaneous dE/dx and momentum measurements. Cross sections and particle fractions for ..pi../sup + -/, k/sup + -/, and p(anti p) are given as a function of several variables. Predictions of various hadronization models are compared to the data. A comparison is made with other fragmentation processes.
Date: September 1, 1987
Creator: Wolf, Z.
Partner: UNT Libraries Government Documents Department

The interplay of nuclear and atomic physics in the synthesis of the elements

Description: In many astronomical environments, physical conditions are so extreme that matter is almost completely ionized. The absence of bound atomic electrons can dramatically alter the decay rates of a number of radioactive nuclei. Several examples of this interplay of nuclear and atomic physics relevant to the synthesis of the chemical elements are described. 16 refs., 4 figs.
Date: March 1, 1989
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

Analysis of low energy beta-emitters

Description: A survey was made of the instruments used for the determination of low energy beta radioactivity. Techniques commonly used are gas flow proportional counting, liquid scintillation counting, solid scintillation counting, and internal ionization chamber counting, solid state detector counting, and radiochemical separation followed by counting using one of the preceeding techniques. The first four techniques were examined and compared with each other. The sensitivities of the techniques were compared on the basis of the detection limits quoted for instruments described in the technical and reviewed literature. The detection limits were then related to the occupational and public individual maximum levels for air and water. Attention is focused primarily on the continuous monitoring of air for /sup 3/H and /sup 85/Kr, a medium energy ..beta..-emitter. It is clear that several continuous air monitoring instruments are readily available for measuring low energy ..beta.. concentrations, even in presence of certain other activity, at occupational levels. However, these instruments do not typically have sensitivities comparable to the public individual levels. Moreover, their capabilities for giving results in real time and for differentiating among the radionuclides actually present is limited.
Date: October 1, 1979
Creator: Murphy, D.L.
Partner: UNT Libraries Government Documents Department

Hydrolysis, formation and ionization constants at 25/sup 0/C, and at high temperature-high ionic strength

Description: Thermochemical data for nuclear waste disposal are compiled. The resulting computerized database consists of critically evaluated data on Gibbs energy of formation, enthalpy of formation, entropy and heat capacity of selected substances for about 16 elements at 25/sup 0/C and zero ionic strength. Elements covered are Am, As, Br, C, Cl, F, I, Mo, Np, N, O, P, Pu, Si, Sr, S, and U. Values of these thermodynamic properties were used to calculate equilibrium quotients for hydrolysis, complexation and ionization reactions up to 300/sup 0/C and 3 ionic strength, for selected chemical reactions.
Date: February 1, 1985
Creator: Phillips, S.L.; Phillips, C.A. & Skeen, J.
Partner: UNT Libraries Government Documents Department

Shape-resonance-enhanced nuclear motion effects in electron-molecule scattering and molecular photoionization. [Review]

Description: Shape resonances in the electronic continuum of molecules induce strong coupling between vibrational and electronic motion over a spectral range much broader than the resonance half width. In photoionization, this coupling causes large deviations from Franck-Condon intensity distributions and strong dependence of photoelectron angular distributions on the vibrational state of the residual ion. In electron scattering, it enhances vibrational excitation. Recent work is reviewed in which new, observable manifestations of this coupling were predicted theoretically and then verified experimentally. 67 references.
Date: January 1, 1979
Creator: Dehmer, J.L. & Dill, D.
Partner: UNT Libraries Government Documents Department

Mechanisms for radiation damage in DNA. Progress report, November 1, 1978-October 31, 1979

Description: Several mechanisms for radiation damage to DNA constituents and DNA are proposed, and a series of experiments utilizing electron spin resonance spectrometry to test the proposed mechanisms are detailed. In the past we have concentrated chiefly on the direct affect of radiation on DNA. We are currently investigating systems of DNA constituents and peptides which may shed light on indirect effects. Studies which have been completed during the past year include: (1) studies of ..gamma..-irradiated N-acetyl amino acids and peptide solutions at 77/sup 0/K; and (2) studies of barriers to hindered rotation in peptide radicals. Studies in which progress has been made in this past year include: (1) ..pi.. cations produced in DNA bases by hydroxyl radical attack; and (2) studies of spin transfer in ..gamma..-Irradiated nucleoside-peptide solutions. These studies have shown that: (1) frozen aqueous solutions provide a suitable matrix for ..gamma.. irradiation studies; (2) ..gamma..-irradiated peptides in frozen aqueous solutions follow chemistry expected from previous studies; and (3) ..pi.. cations of DNA base can be produced by hydroxyl radical attack.
Date: July 1, 1979
Creator: Sevilla, M.D.
Partner: UNT Libraries Government Documents Department

Photoelectron spectroscopy of heavy atoms and molecules

Description: The importance of relativistic interactions in the photoionization of heavy atoms and molecules has been investigated by the technique of photoelectron spectroscopy. In particular, experiments are reported which illustrate the effects of the spin-orbit interaction in the neutral ground state, final ionic states and continuum states of the photoionization target.
Date: July 1, 1979
Creator: White, M.G.
Partner: UNT Libraries Government Documents Department

Interaction of rare gas metastable atoms. [Differential and total cross sections, elastic scattering, ionization, potential scattering, phase shifts, rate constants]

Description: The physical and chemical properties of metastable rare gas atoms are discussed and summarized. This is followed by a detailed examination of the various possible pathways whereby the metastable's excess electronic energy can be dissipated. The phenomenon of chemi-ionization is given special emphasis, and a theoretical treatment based on the use of complex (optical) potential is presented. This is followed by a discussion on the unique advantages offered by elastic differential cross section measurements in the apprehension of the fundamental forces governing the ionization process. The methodology generally adopted to extract information about the interaction potential for scattering data is also systematically outlined. Two widely studied chemi-ionization systems are then closely examined in the light of accurate differential cross section measurements obtained in this work. The first system is He(2/sup 3/S) + Ar for which one can obtain an interaction potential which is in good harmony with the experimental results of other investigators. The validity of using the first-order semiclassical approximation for the phase shifts calculation in the presence of significant opacities is also discussed. The second reaction studied is He*+D/sub 2/ for which measurements were made on both spin states of the metastable helium. A self-consistent interaction potential is obtained for the triplet system, and reasons are given for not being able to do likewise for the singlet system. The anomalous hump proposed by a number of laboratories is analyzed. Total elastic and ionization cross sections as well as rate constants are calculated for the triplet case. Good agreement with experimental data is found. Finally, the construction and operation of a high power repetitively pulsed nitrogen laser pumped dye laser system is described in great details. Details for the construction and operation of a flashlamp pumped dye laser are likewise given.
Date: November 1, 1977
Creator: Wang, A.Z.F.
Partner: UNT Libraries Government Documents Department

Molecular beam photoionization and gas-surface scattering

Description: The energetics of the ethylene ion-molecule reactions was investigated in more detail than previously possible in two body collision experiments by photoionization of the neutral van der Waals ethylene dimer. The stability of the (C/sub 2/H/sub 4/)/sup +/C/sub 2/H/sub 4/ ion-molecule collision complex has been determined to be 18.2 +- 0.5 kcal. The highest potential barriers along the reaction coordinate for decomposition of this collision complex into C/sub 4/H/sub 7//sup +/ + H and C/sub 3/H/sub 5//sup +/ + CH/sub 3/ have been determined to be 0 +- 1.5 and 8.7 +- 1.5 kcal. In a similar manner, the energetics of the solvated ethylene dimer ion was investigated by the photoionization of the ethylene trimer. The absolute proton affinity of NH/sub 3/ (203.6 +- 1.3 kcal/mole) and the proton solvation energies by more than one NH/sub 3/ have been determined by molecular beam photoionization. In addition, the NH/sub 3//sup +/-NH/sub 3/ interaction energy (0.79 +- 0.05 eV) was measured by photoionization of the neutral van der Waals dimer. These experiments have shown that photoionization of van der Waals clusters is a very powerful method of determining the energetics of gas phase proton solvation. The scattering of helium atomic beams from a high Miller index platinum surface that exhibits ordered, periodic steps on the atomic scale to probe the effect of atomic steps on the scattering distribution is explored. Rainbow scattering is observed when the step edges are perpendicular to the incident helium atoms. The design, construction and operation of a beam-surface scattering apparatus are described. The first data obtained in this apparatus are presented and the interesting dynamical aspects of the oxidation of D, D/sub 2/ and CO are discussed. 75 references.
Date: September 1, 1979
Creator: Ceyer, S.T.
Partner: UNT Libraries Government Documents Department

Muon energy loss at high energy and implications for detector design

Description: We study the effects of energy loss and associated electromagnetic showers on muon tracking and momentum measurement in muon detectors operating in the energy range 100 GeV-5 TeV. A detailed Monte Carlo simulation tracks muons and shower particles through a detector structure and evaluates the charged-particle environment in chambers. We find that catastrophic energy loss events accompanied by energetic showers can pose serious problems to designers of muon spectrometers. 14 refs., 6 figs.
Date: November 1, 1987
Creator: Eastman, J.J. & Loken, S.C.
Partner: UNT Libraries Government Documents Department

Studies of the formation, chemical reactivity, and properties of small clusters: Application to an understanding of aerosol formation and heterogeneous chemistry

Description: The small cluster program involves (1) studies of reactions related to formation and growth of heteromolecular clusters and their thermochemical properties, (2) studies of photoinitiated processes in clusters, (3) investigations related to heterogeneous reactions including the influence of reaction centers on the interconversion, and (4) theoretical calculations of properties, dynamics, and structure. A major thrust of the work during the past year has been devoted to a study of the role of ionization and the presence of ions on reactions and energetics. During the past few months, particular attention has been paid to systems having varying proton affinities. From the data, we can determine the influence of these values on the nature of the reactions and ascertain the ultimate chemical nature of the ionization center formed as a result of the reactions. 83 refs., 12 figs., 2 tabs.
Date: January 1, 1990
Creator: Castleman, A.W. Jr.
Partner: UNT Libraries Government Documents Department

Laser-synchrotron hybrid experiments: A photon to tickle, a photon to poke''

Description: In this paper we present the preliminary results from a new experimental technique to synchronize the pulses from a mode-locked NdYAG laser to the light pulses in the VUV storage ring at the National Synchrotron Light Source (NSLS). We describe a method to electronically change the delay time between the laser pulses and the synchrotron pulses. We also illustrate a method to overlap the synchrotron pulses with the laser pulses in space and time. Preliminary results will be presented for two experiments.
Date: January 1, 1991
Creator: Ederer, D.L.; Rubensson, J.E.; Mueller, D.R. (National Inst. of Standards and Technology, Gaithersburg, MD (United States)); Shuker, R. (Ben-Gurion Univ. of the Negev, Beersheba (Israel)); O'Brien, W.L.; Jai, J. et al.
Partner: UNT Libraries Government Documents Department

Recent fission cross section standards measurements

Description: The /sup 235/U(n,f) reaction is the standard by which most neutron induced fission cross sections are determined. Most of these cross sections are derived from relatively easy ratio measurements to /sup 235/U. However, the more difficult /sup 235/U(n,f) cross section measurements require the use of advanced neutron detectors for the determination of the incident neutron fluence. Examples of recent standard cross section measurements are discussed, various neutron detectors are described, and the status of the /sup 235/U(n,f) cross section standard is assessed. 23 refs., 8 figs., 4 tabs.
Date: January 1, 1985
Creator: Wasson, O.A.
Partner: UNT Libraries Government Documents Department

Neutron dosimetry at SLAC: Neutron sources and instrumentation

Description: This report summarizes in detail the dosimetric characteristics of the five radioisotopic type neutron sources ({sup 238}PuBe, {sup 252}Cf, {sup 238}PuB, {sup 238}PuF{sub 4}, and {sup 238}PuLi) and the neutron instrumentation (moderated BF{sub 3} detector, Anderson-Braun (AB) detector, AB remmeter, Victoreen 488 Neutron Survey Meter, Beam Shut-Off Ionization Chamber, {sup 12}C plastic scintillator detector, moderated indium foil detector, and moderated and bare TLDs) that are commonly used for neutron dosimetry at the Stanford Linear Accelerator Center (SLAC). 36 refs,. 19 figs.
Date: October 1, 1991
Creator: Liu, J.C.; Jenkins, T.M.; McCall, R.C. & Ipe, N.E.
Partner: UNT Libraries Government Documents Department

Measurement of intensity-dependent rates of above-threshold ionization (ATI) of atomic hydrogen at 248 nm

Description: Measured rates of multiphoton ionization (MPI) from the ground state of atomic hydrogen by a linearly polarized, subpicosecond KrF laser pulse at 248 nm wavelength are compared to predictions of lowest-order perturbation theory, Floquet theory, and Keldysh-Faisal-Reiss (KFR) theory with and without Coulomb correction for peak irradiance of 3 {times} 10{sup 12}W/cm{sup 2} to 2 {times} 10{sup 14}W/cm{sup 2}. The Coulomb-corrected Keldysh model falls closest to the measured rates, the others being much higher or much lower. At 5 {times} 10{sup 13}W/cm{sup 2}, the number of ATI electrons decreased by a factor of approximately 40 with each additional photon absorbed. ATI of the molecular hydrogen background and of atoms from photodissociation of the molecules were also observed. The experiment employed a crossed-beam technique at ultrahigh vacuum with an rf-discharge atomic hydrogen source and a magnetic-bottle type electron time-of-flight spectrometer to count the electrons in the different ATI channels separately. The apparatus was calibrated to allow comparison of absolute as well as relative ionization rates to the theoretical predictions. This calibration involved measuring the distribution of irradiance in a focal volume that moved randomly and changed its size from time to time. A data collection system under computer control divided the time-of-flight spectra into bins according to the energy of each laser pulse. This is the first measurement of absolute rates of ATI in atomic hydrogen, and the first measurement of absolute test of MPI in atomic hydrogen without a large factor to account for multiple modes in the laser field. As such, the results of this work are important to the development of ATI theories, which presently differ by orders of magnitude in their prediction of the ionization rates. They are also important to recent calculations of temperatures in laser-heated plasmas, many of which incorporate KFR theory.
Date: April 1, 1991
Creator: Nichols, T.D.
Partner: UNT Libraries Government Documents Department

Chemistry of lower valent actinide halides

Description: This research effort was concerned almost entirely with the first two members of the actinide series, thorium and uranium, although the work was later extended to some aspects of the neptunium-fluorine system in a collaborative program with Los Alamos National Laboratory. Detailed information about the lighter actinides will be helpful in modeling the properties of the heavier actinide compounds, which will be much more difficult to study experimentally. In this program, thermochemical information was obtained from high temperature equilibrium measurements made by effusion-beam mass spectrometry and by effusion-pressure techniques. Data were derived primarily from second-law analysis so as to avoid potential errors in third-law calculations resulting from uncertainties in spectroscopic and molecular constants. This approach has the additional advantage of yielding reaction entropies that can be checked for consistency with various molecular constant assignments for the species involved. In the U-F, U-Cl, and U-Br systems, all of the gaseous species UX, UX{sub 2}, UX{sub 3}, UX{sub 4}, and UX{sub 5}, where X represents the halogen, were identified and characterized; the corresponding species ThX, ThX{sub 2}, ThX{sub 3}, and ThX{sub 4} were studied in the Th-F, Th-Cl, and Th-Br systems. A number of oxyhalide species in the systems U-0-F, U-0-Cl, Th-0-F, and Th-O-Cl were studied thermochemically. Additionally, the sublimation thermodynamics of NpF{sub 4}(s) and NpO{sub 2}F{sub 2}(s) were studied by mass spectrometry.
Date: January 1, 1992
Creator: Lau, K.H. & Hildenbrand, D.L.
Partner: UNT Libraries Government Documents Department

Fusion Energy Division annual progress report period ending December 31, 1983

Description: The Fusion Program carries out work in a number of areas: (1) experimental and theoretical research on two magnetic confinement concepts - the ELMO Bumpy Torus (EBT) and the tokamak, (2) theoretical and engineering studies on a third concept - the stellarator, (3) engineering and physics of present-generation fusion devices, (4) development and testing of diagnostic tools and techniques, (5) development and testing of materials for fusion devices, (6) development and testing of the essential technologies for heating and fueling fusion plasmas, (7) development and testing of the superconducting magnets that will be needed to confine these plasmas, (8) design of future devices, (9) assessment of the environmental impact of fusion energy, and (10) assembly and distribution to the fusion community of data bases on atomic physics and radiation effects. The interactions between these activities and their integration into a unified program are major factors in the success of the individual activities, and the ORNL Fusion Program strives to maintain a balance among these activities that will lead to continued growth.
Date: September 1, 1984
Partner: UNT Libraries Government Documents Department

Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements

Description: The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; [sup 238]U-[sup 230]Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.
Date: January 1, 1992
Creator: Wasserburg, G.J.
Partner: UNT Libraries Government Documents Department

Energy transfer and non-linear optical properties at near ultraviolet wavelengths: Rare earth 4f yields 5d transitions in crystals and glasses

Description: The following topics were studied: two-photon transitions from 4f ground state to 5d excited states in Ce{sup 3+}:CaF{sub 2}; optical absorption and photoionization measurements from excited state of Ce{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12}; excited state photoionization of Ce{sup 3+} ions in Ce{sub 3+}:CaF{sub 2}; optical gain and loss studies in Ce{sup 3+}:LiYF{sub 4}; Gd {yields}Cr energy transfer in Cr{sup 3+}:GSGG, Cr{sup 3+}:GSAG and Cr{sup 3+}:GGG crystals; nonradiative relaxation in Ce{sup 3+} doped crystals and glasses; and grating formation in impurity doped crystals.
Date: August 1, 1992
Creator: Hamilton, D.S.
Partner: UNT Libraries Government Documents Department

Science with multiply-charged ions at Brookhaven National Laboratory

Description: Methods for producing multiply-charged ions at different charge states and energies were discussed in the context of the facilities and capabilities that are part of the atomic physics program at Brookhaven. Examples were given of some of the experiments that have been accomplished. It was shown that ions with energies from a fraction of an MeV to ions with an energy of several hundred MeV are necessary to properly investigate the science of low-energy multiply-charged ions. Also discussed was the use of synchrotron photons as a fertile method for extending the field of ionic studies.
Date: January 1, 1987
Creator: Jones, K.W.; Johnson, B.M.; Meron, M. & Thieberger, P.
Partner: UNT Libraries Government Documents Department

Low energy ion-molecule reaction dynamics and chemiionization kinetics. Progress report, February 1, 1978--January 31, 1979. [Summaries of research activities at University of Rochester]

Description: A crossed molecular beam apparatus for the study of low energy ion-molecule reactions and free-radical chemiionization kinetics was constructed, and its initial work was in the study of reactions of H/sub 2//sup +/ + CO, N/sub 2/, and Ar at energies between 5 and 10 eV. The preliminary results obtained indicate that in the energy range studied, the reactions proceed via impulsive, direct collisions. The molecular ion products are scattered in the backward direction with respect to the incoming H/sub 2//sup +/ projectile with translational energy in excess of that predicted by spectator stripping. Also completed was the construction of a discharge ion-source with a sample vaporization compartment, allowing solids and liquids to be used as source materials. This source will be used to prepare HCO/sup +/ beams for studies of reactions such as HCO/sup +/ + H/sub 2/O/sup +/ H/sub 3/O/sup +/ + CO, considered important in hydrocarbon flames.
Date: January 1, 1979
Creator: J.M., Farrar
Partner: UNT Libraries Government Documents Department

[Aspects of photoionization of impurities and electron transfer in ionic crystals]

Description: Spectral evidence was found for photoionization in spectra of Eu[sup 2+] and Sm[sup 3+] in BaF[sub 2]; Ce[sup 3+] was also studied in BaF[sub 2], CaF[sub 2], and SrF[sub 2]. Two-photon spectroscopy of forbidden transitions (zero-phonon lines) was extended from NaF: Cu[sup +] to Mn[sup 4+] in Cs[sub 2]GeF[sub 6] and to MgO:Ni[sup 2+].
Date: February 10, 1993
Creator: McClure, D.S.
Partner: UNT Libraries Government Documents Department

Status of the Los Alamos tritium beta decay experiment

Description: The Los Alamos tritium experiment employs a gaseous tritium source and a magnetic spectrometer to determine the mass of the electron antineutrino from the shape of the tritium beta spectrum. Since publication of the first result from this apparatus (m/sub nu/ < 27 eV at 95% confidence), work has concentrated on improving the data rates. A 96-element Si microstrip array detector has been installed to replace the single proportional counter at the spectrometer focus, resulting in greatly increased efficiency. Measurements of the 1s photoionization spectrum of Kr now obviate the need for reliance on the theoretical shakeup and shakeoff spectrum of Kr in determining the spectrometer resolution. 19 refs., 3 figs.
Date: January 1, 1989
Creator: Robertson, R.G.H.; Bowles, T.J.; Wark, D.L.; Wilkerson, J.F. & Knapp, D.A.
Partner: UNT Libraries Government Documents Department