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Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans Apr 1999

Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans

Theses and Dissertations

Multiplexed Compton Scatter Tomography (MCST) is explored as a method of nondestructively generating cross-sectional images of a sample's electron density. MCST is viable when access is available to only one side of the sample because it registers scattered gamma radiation. Multiplexing in scattered photon energy and in detector position allows simultaneous interrogation of many voxels with comparatively wide collimation. Primary components include a radioisotope source, fan beam collimators, and energy-discriminating detectors. The application of MCST to inspecting aluminum airframes for corrosion is considered. This application requires source gammas near 100 keV where the scattered gamma energy is severely broadened by …

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In Situ Measurement Of The Aerosol Size Distribution In Stratospheric Solid Rocket Motor Exhaust Plumes, Martin N. Ross, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins Apr 1999

In Situ Measurement Of The Aerosol Size Distribution In Stratospheric Solid Rocket Motor Exhaust Plumes, Martin N. Ross, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins

Chemistry Faculty Research & Creative Works

The concentration and size distribution of aerosol in the stratospheric exhaust plumes of two Space Shuttle rockets and one Titan IV rocket were measured using a two component aerosol sampling system carried aboard a WB‐57F aircraft. Aerosol size distribution in the 0.01 µm to 4 µm diameter size range was measured using a two component sampling system. The measured distributions display a trimodal form with modes near 0.005 µm, 0.09 µm, and 2.03 µm and are used to infer the relative mass fractionation among the three modes. While the smallest mode has been estimated to contain as much as 10% …

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Virtual Compton Scattering Processes In Quantum Chromodynamics, Igor V. Musatov Apr 1999

Virtual Compton Scattering Processes In Quantum Chromodynamics, Igor V. Musatov

Physics Theses & Dissertations

Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual Parton distributions for the case when long-distance information is accumulated in nonforward matrix elements [special characters omitted] of quark and gluon light-cone operators. We consider different aspects of the investigation of the virtual Compton amplitude in the QCD on two examples: the spin dependent observables in the forward virtual Compton process (measured in the experiments on deep inelastic scattering) and the γγ* transition form factor. Then we discuss in detail evolution equations for non-forward parton distributions [special characters omitted] The …

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State To State Ne-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane Mar 1999

State To State Ne-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane

Peer Reviewed Articles

Measurements of state-to-state integral cross sections for rotational excitation of CO by collisions with Ne are reported. The measurements were performed in crossed molecular beams with resonance enhanced multiphoton detection at collision energies of 711 and 797 cm-1. The cross sections display strong interference structure, with a propensity for odd Δj below Δj=10. Predictions of the ab initio potential surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)] and the new ab initio surface of McBane and Cybulski [J. Chem. Phys. 110, 11734 (1999), preceding paper] are compared to the …

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An Ab Initio Potential Energy Surface For The Ne-Co, George C. Mcbane, Slawomir M. Cybulski Mar 1999

An Ab Initio Potential Energy Surface For The Ne-Co, George C. Mcbane, Slawomir M. Cybulski

Peer Reviewed Articles

A new ab initio two-dimensional potential energy surface for the Ne-CO interaction is described. The surface was obtained by the supermolecule method at the CCSD(T) level of theory. It is compared with several experimental data sets and with the symmetry-adapted perturbation theory (SAPT) surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)]. The new surface gives modestly better predictions of experimental results that depend on close approach of Ne to CO, but does not describe the ground state geometry as well as the SAPT surface.

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The Cleo-Iii Rich Detector And Beam Test Results, Raymond Mountain, J.C. Wang, Marina Artuso, R. Ayad Mar 1999

The Cleo-Iii Rich Detector And Beam Test Results, Raymond Mountain, J.C. Wang, Marina Artuso, R. Ayad

Physics - All Scholarship

We are constructing a Ring Imaging Cherenkov detector (RICH) for the CLEO III upgrade for precision charged hadron identification. The RICH uses plane and sawtooth LiF crystals as radiators, MWPCs as photon detectors with TEA as the photo-sensitive material, and low-noise Viking readout electronics. Results of a beam test of the first two out of total 30 sectors are presented.

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Renormalized Effective Qcd Hamiltonian: Gluonic Sector, David G. Robertson, E.S. Swanson, A.P. Szczepaniak, C.R. Ji, S.R. Cotanch Mar 1999

Renormalized Effective Qcd Hamiltonian: Gluonic Sector, David G. Robertson, E.S. Swanson, A.P. Szczepaniak, C.R. Ji, S.R. Cotanch

Physics Faculty Scholarship

Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which generates an effective Hamiltonian for the gluon sector. The formulation is in the Coulomb gauge where the QCD Hamiltonian is renormalizable and the Gribov problem can be resolved. We utilize elements of the Głazek and Wilson regularization method but now introduce a continuous cut-off procedure which eliminates non-local counterterms. The effective Hamiltonian is then derived to second order in the strong coupling constant. The resulting renormalized Hamiltonian provides a realistic starting point for approximate many-body calculations of hadronic properties for systems with explicit gluon degrees of freedom.

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Search For New Particles Decaying To Bb̅ In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Mar 1999

Search For New Particles Decaying To Bb̅ In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have used 87 pb-1 of data collected with the collider detector at Fermilab to search for new particles decaying to bb̅. We present model-independent upper limits on the cross section for narrow resonances which exclude the color-octet technirho in the mass interval 350 < M < 440 GeV/c2. In addition, we exclude top-gluons, predicted in models of top-color-assisted technicolor, of width Γ= 0.3M in the mass range 280 < M < 670 GeV/c2, of width Γ= 0.5M in the mass range 340 < M < 640 GeV/c2, and of width Γ= 0.7M in the mass range 375 < M < 560 GeV/c2.

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Parity Nonconservation In Neutron Resonances In 133cs, E I. Sharapov, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, Sharon L. Stephenson, Y-F Yen, V W. Yuan Mar 1999

Parity Nonconservation In Neutron Resonances In 133cs, E I. Sharapov, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Spatial parity nonconservation (PNC) has been studied in the compound-nuclear states of 134Cs by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick 133Cs target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range from 5 to 400 eV. A total of 28 new p-wave resonances were found, their neutron widths determined, and the PNC longitudinal asymmetries of the resonance cross sections measured. The value obtained for the root-mean-square PNC element M=(0.06-0.02+0.25) meV in 133 …

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Residual Native Shallow Donor In Zno, David C. Look, Joseph W. Hemsky, J. R. Sizelove Mar 1999

Residual Native Shallow Donor In Zno, David C. Look, Joseph W. Hemsky, J. R. Sizelove

Physics Faculty Publications

High-energy electron irradiation in ZnO produces shallow donors at about EC-30meV. Because the production rate is much higher for Zn-face (0001) than O-face (0001̅ ) irradiation, the donor is identified as a Zn-sublattice defect, most likely the interstitial ZnI or a ZnI-related complex. The donor energy is quite close to that of the unirradiated sample, and of other samples discussed in the literature, strongly suggesting that ZnI (and not VO) is the dominant native shallow donor in ZnO. An exceptionally high displacement threshold energy (∼1.6MeV) is quantitatively explained in terms of a …

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Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil Mar 1999

Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil

Theses and Dissertations

This laboratory thesis investigated the applicability of reflectance spectroscopy as a tool to measure desorption rates by directly observing the change in trichloroethylene bound to surface sites. Diffuse reflectance spectroscopy holds the promise of being a faster technique with minimal sample preparation time. Reflectance spectroscopy's dependence on the surface of the sample is its greatest advantage, as well as its greatest disadvantage. Both high and low resolution scans were made of different soil samples contaminated by trichloroethylene. After the technique of spectral subtraction was used, potential TCE signals were observed from the dolomitic limestone sample. Unfortunately, due to the low …

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Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts Mar 1999

Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts

Theses and Dissertations

The Multiplexed Compton Scatter Tomograph (MCST) uses single back-scattered photons to image electron density in aluminum. A source of error in this imaging technique is the presence of multiple scatters. This thesis studies the double scatter spectrum as an approximation of the multiple scatter spectrum. A deterministic code called Monte Carlo Double Scatter (MOCADS) was developed to investigate the double scatter spectrum. The code includes calculations of the Rayleigh scatter, Compton scatter, Doppler broadening effects of the spectrum, and polarization effects following the Compton scatter. The Doppler broadening portion of the code was validated by a deterministic code called Scatgram. …

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Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday Mar 1999

Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday

Theses and Dissertations

Initial efforts to characterize the scattering dynamics of B + H2 focus on computing scattering matrix elements for the fine structure transition B (2P1/2) --> B (2P3/2) in collisions with H2, allowing for rotational excitation. Using a new application of the time dependent Channel Packet Method (CPM), reactant and product wave packets are prepared in the asymptotic limit on the B (2P1/2) and B (2P3/2) surfaces. They are propagated using the split operator method together wit a unitary transformation between the …

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Band Structure Anisotropy In Semiconductor Quantum Wells, Steven J. Novotny Mar 1999

Band Structure Anisotropy In Semiconductor Quantum Wells, Steven J. Novotny

Theses and Dissertations

The focus of this research is an investigation of energy band anisotropy in simple quantum well structures. This anisotropy results from the asymmetry of the periodic potential within the crystal lattice. For sufficiently high doping levels, band structure anisotropy is expected to play an important role in the evaluation of the electronic and optical properties of the quantum well structures. The analysis uses a model based on a 6x6 Luttinger-Kohn k.p approach for bulk material valence band structure together with the Envelope Function Approximation. The model is used to analyze Si/SiGe, AlGaAs/GaAs, and GaAs/InGaAs quantum wells for the 001 and …

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Active Multispectral Band Selection And Reflectance Measurement System, Bradley D. Rennich Mar 1999

Active Multispectral Band Selection And Reflectance Measurement System, Bradley D. Rennich

Theses and Dissertations

Due to system design requirements, an active multispectral laser radar system may be limited in the number of spectral bands that can be integrated into the system. To aid in the selection of these bands, a novel multispectral band selection technique is presented based on the cross-correlation of the material class reflectance spectra over a wavelength range of 1 - 5 microns. The algorithm uses directional hemispherical reflectance data from the Nonconventional Exploitation Factors database to select a number of spectral bands for classification purposes. Because the target material spectral reflectance is so important to the performance of an active …

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Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath Mar 1999

Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath

Theses and Dissertations

Electrical characterization has been performed on ion-implanted p-type 4H-SiC to assess the activation efficiency and implantation-related damage recrystallization with the intention of developing an implantation/annealing scheme. Low doped (Na - Nd = 5x1015cm3 epitaxial p-type layers grown by MOCVD were implanted with Al or B at doses ranging from 1x1013 to 1x1014/cm2 at room temperature or 500°C. The electrical technique of Temperature Dependent Hall Effect (TDHE) indicated that Al and B act as shallow acceptors 4H-SiC with ionization energies of ~252 and ~285 meV, respectively. The highest activation efficiency for Al and B …

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Double Layer Effects On Shock Wave Propagation, Shannon L. Walker Mar 1999

Double Layer Effects On Shock Wave Propagation, Shannon L. Walker

Theses and Dissertations

An analysis and assessment of two mechanisms in plasma shock interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of a spatially-dependent electron temperature and additional electron impact ionization at the shock front were examined for effects on shock structure and propagation. These mechanisms were incorporated into an existing one-dimensional, time-dependent, fluid dynamics code that uses the Riemami problem as a basis and numerically solves the Euler equations for two fluids: the neutral gas and the charged component. The spatial variation in electron temperature was modeled as a shock-centered rise in temperature. Additional ionization …

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Optimization Of A Multilayer Photothermal Sensor For Infrared Spectroscopy, Janine O.J. Wiggins Mar 1999

Optimization Of A Multilayer Photothermal Sensor For Infrared Spectroscopy, Janine O.J. Wiggins

Theses and Dissertations

Tri-layer thermal diffusion modeling was applied to the optimization of a multi-layer reed sensor for use in a photothermal infrared detector. The multi-layer reed sensor deflects in response to increased temperature. Deflection, of angstroms or larger, is measured using an atomic force microscope. A newly developed thermal diffusion model for three layer reeds was combined with an existing two-layer cantilever model, in order to explore the effects of length, operating frequency, and layer thickness on signal to noise ratio. Model behavior is presented, and compared to laboratory results.

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Measurement Of ZT0 And Drell-Yan Production Cross Sections Using Dimuons In P̅P Collisions At √S =1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Mar 1999

Measurement Of ZT0 And Drell-Yan Production Cross Sections Using Dimuons In P̅P Collisions At √S =1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of Z0 boson and Drell-Yan production cross sections in p̅p collisions at √s =1.8 TeV using a sample of 107 pb-1 accumulated by the Collider Detector at Fermilab. The Drell-Yan cross section is measured in the mass range of Mμμ>40 GeV/c2. We compare the measurements with the predictions of quantum chromodynamics in both leading order and next-to-leading order, incorporating the recent parton distribution functions. The measurements are consistent with the standard model expectations.

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The Cleo-Iii Ring Imaging Cherenkov Detector, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar Feb 1999

The Cleo-Iii Ring Imaging Cherenkov Detector, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar

Physics - All Scholarship

The CLEO-III Detector upgrade for charged particle identification is discussed. The RICH design uses solid LiF crystal radiators coupled with multi-wire chamber photon detectors, using TEA as the photosensor, and low-noise Viking readout electronics. Results from our beam test at Fermilab are presented.

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Parity Violation In Neutron Resonances In 107,109ag, L Y. Lowie, J D. Bowman, J Corvi, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, H M. Shimizu Feb 1999

Parity Violation In Neutron Resonances In 107,109ag, L Y. Lowie, J D. Bowman, J Corvi, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, H M. Shimizu

Physics and Astronomy Faculty Publications

Parity nonconservation (PNC) was studied in p-wave resonances in Ag by measuring the helicity dependence of the neutron total cross section. Transmission measurements on natural Ag were performed in the energy range 32 to 422 eV with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at Los Alamos National Laboratory. A total of 15 p-wave neutron resonances were studied in 107Ag and ninep-wave resonances in 109Ag. Statistically significant asymmetries were observed for eight resonances in 107Ag and for four resonances in109Ag. An analysis treating the PNC matrix elements as random variables yields a …

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Exposure To Atmospheric Radon, Daniel J. Steck, R. William Field, Charles F. Lynch Feb 1999

Exposure To Atmospheric Radon, Daniel J. Steck, R. William Field, Charles F. Lynch

Physics Faculty Publications

We measured radon (222Rn) concentrations in Iowa and Minnesota and found that unusually high annual average radon concentrations occur outdoors in portions of central North America. In some areas, outdoor concentrations exceed the national average indoor radon concentration. The general spatial patterns of outdoor radon and indoor radon are similar to the spatial distribution of radon progeny in the soil. Outdoor radon exposure in this region can be a substantial fraction of an individual's total radon exposure and is highly variable across the population. Estimated lifetime effective dose equivalents for the women participants in a radon-related lung cancer …

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Measurement Of The Mass Splittings Between The Bb̅ΧB,J(1P) States, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration Feb 1999

Measurement Of The Mass Splittings Between The Bb̅ΧB,J(1P) States, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We present new measurements of photon energies and branching fractions for the radiative transitions Υ(2S) → γχb(J=0,1,2)(1P). The masses of the χb states are determined from the measured radiative photon energies. The ratio of mass splittings between the χb substates, r ≡ [(MJ=2 -MJ=1)/( MJ=1 - MJ=0), with M the χb mass, provides information on the nature of the bb̅ confining potential. We find r(1P)=0.542 ±0.022±0.024. This value is somewhat lower than the previous world average, but more consistent with …

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Evidence Of Dynamic Jahn-Teller Distortions In Two-Dimensional Crystalline Molecular Films, Jaewu Choi, Peter A. Dowben, C.N. Borca, Shireen Adenwalla, A.V. Bune, Stephen Ducharme, V.M. Fridkin, S.P. Palto, N. Petukhova Jan 1999

Evidence Of Dynamic Jahn-Teller Distortions In Two-Dimensional Crystalline Molecular Films, Jaewu Choi, Peter A. Dowben, C.N. Borca, Shireen Adenwalla, A.V. Bune, Stephen Ducharme, V.M. Fridkin, S.P. Palto, N. Petukhova

Peter Dowben Publications

The surface electronic structure in crystalline copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%) has been studied by photoemission and inverse photoemission as a function of alkali metal (sodium) doping. Sodium doping introduces at least two new states into the band (HOMO-LUMO) gap well away from the Fermi level. While the sodium-doped copolymer is observed to resemble an n-type semiconductor, the change in electronic structure with temperature suggests that dynamic distortions lead to a photoemission initial state splitting of the lower Hubbard-like bands. There is a decrease in the effective Debye temperature with sodium doping which may, in turn, …

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Measurement Of The Top Quark Mass With The Collider Detector At Fermilab, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Jan 1999

Measurement Of The Top Quark Mass With The Collider Detector At Fermilab, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a new measurement of the top quark mass in tt̅ events in which both W bosons from top quarks decay into leptons (eν, μν). We use events collected by the CDF experiment from pp̅ collisions at √s =1.8 TeV at the Tevatron collider. We measure a top quark mass of 167.4 ± 10.3(stat) ± 4.8(syst) GeV/c2 from a sample of eight events. We combine this result with previous CDF measurements in other decay channels to obtain a final mass value of 176.0 ± 6.5 GeV/c2.

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Does N-2(-) Exist? A Coupled-Cluster Study, Gennady L. Gutsev, Piotr B. Rozyczko, Rodney J. Bartlett, Charles A. Weatherford Jan 1999

Does N-2(-) Exist? A Coupled-Cluster Study, Gennady L. Gutsev, Piotr B. Rozyczko, Rodney J. Bartlett, Charles A. Weatherford

Physics Publications

Potential energy curves of the ground-state N2 molecule and its doublet N−2 anion are calculated at the coupled-cluster level with single and double excitations and with noniterative triples [CCSD(T)] as well as with the multireference averaged-quadratic coupled-cluster (MR-AQCC) method. The N−2 anion is shown to be temporary and decays to its neutral parent plus a free electron at bond lengths shorter than ≈1.4 and larger than ≈2.5 Å. Thus, the N−2 anion exists within the 1.4⩽R(N–N)⩽2.5 Å range at the Born–Oppenheimer approximation.

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Thermodynamical Stability Of Ch3ono And Ch3ono-: A Coupled-Cluster And Hartree-Fock-Density-Functional-Theory Study, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett Jan 1999

Thermodynamical Stability Of Ch3ono And Ch3ono-: A Coupled-Cluster And Hartree-Fock-Density-Functional-Theory Study, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett

Physics Publications

The structure and thermodynamic stability of methylnitrite and its anion are studied by the infinite-order coupled-cluster method with all singles and doubles and noniterative inclusion of triple excitations [CCSD(T)] and Hartree–Fock-density-functional theory (HFDFT). We have optimized the geometries and computed the harmonic vibrational frequencies of major fragments, H2, CH, NH, OH, CN, N2, CO, NO, O2, CH2, NH2, H2O, HCN, HNC, HCO, HNO, O2H, CO2, NO2, CH3, NH3, CNH2, HCO2, HNO2, CH3N, CH3O, CH3NO, CH3ON, CH2NO2, and their anions, when the latter exist. Fragmentation energies obtained at both levels of theory are rather close to each other, except for channels …

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Search For Exchange-Antisymmetric Two-Photon States, D. Demille, D. Budker, N. Derr, Edward Deveney Jan 1999

Search For Exchange-Antisymmetric Two-Photon States, D. Demille, D. Budker, N. Derr, Edward Deveney

Physics Faculty Publications

Atomic two-photon J = 0↔J′ = 1 transitions are forbidden for photons of the same energy. This selection rule is related to the fact that photons obey Bose-Einstein statistics. We have searched for small violations of this selection rule by studying transitions in atomic Ba. We set a limit on the probability v that photons are in exchange-antisymmetric states: v<1.2×10-7.

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Midisuperspace Models Of Canonical Quantum Gravity, Charles G. Torre Jan 1999

Midisuperspace Models Of Canonical Quantum Gravity, Charles G. Torre

All Physics Faculty Publications

A midisuperspace model is a field theory obtained by symmetry reduction of a parent gravitational theory. Such models have proven useful for exploring the classical and quantum dynamics of the gravitational field. I present three recent classes of results pertinent to canonical quantization of vacuum general relativity in the context of midisuperspace models. (1) I give necessary and sufficient conditions such that a given symmetry reduction can be performed at the level of the Lagrangian or Hamiltonian.(2) I discuss the Hamiltonian formulation of models based upon cylindrical and toroidal symmetry. In particular, I explain how these models can be identified …

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Evolution Of The Electronic Structure And Properties Of Neutral And Charged Aluminum Clusters: A Comprehensive Analysis, B. K. Rao, P. Jena Jan 1999

Evolution Of The Electronic Structure And Properties Of Neutral And Charged Aluminum Clusters: A Comprehensive Analysis, B. K. Rao, P. Jena

Physics Publications

Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to calculate the global equilibrium geometries and electronic structure of neutral, cationic, and anionic aluminumclusters containing up to 15 atoms. The total energies of these clusters are then used to study the evolution of their binding energy, relative stability, fragmentation channels, ionization potential, and vertical and adiabatic electron affinities as a function of size. The geometries are found to undergo a structural change from two dimensional to three dimensional when the cluster contains 6 atoms. An interior atom emerges only when clusters contain 11 or more atoms. …

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