Bulletin of the American Physical Society
2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section
Volume 53, Number 8
Friday–Saturday, October 10–11, 2008; Dayton, Ohio
Session C3: Chemical Physics |
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Chair: David Weeks, Air Force Institute of Technology Room: Fawcett Hall 206 |
Saturday, October 11, 2008 8:00AM - 8:12AM |
C3.00001: System-averaged exchange and correlation holes in second-row atoms Antonio Cancio Recent work is presented on the theoretical calculation of system-averaged exchange and correlation holes (intracules) for a pseudopotential model of the valence shell of second-row atoms. Exchange holes are obtained from numerical fourier transform methods and correlation holes from variational quantum Monte Carlo calculations using the method of correlated estimates. We observe approximate scaling behavior in both exchange and correlation, following the known scaling of the valence density across the row. The holes are compared to density-functional models including LDA, GGA and meta-GGA approaches. Particular attention is paid to self interaction (SI) error; we find that a sizeable error occurs in the same-spin channel of the correlation hole which persists for the LDA and GGA even after standard SI corrections are applied. A simple SI correction that eliminates this error will be discussed. [Preview Abstract] |
Saturday, October 11, 2008 8:12AM - 8:24AM |
C3.00002: The Adiabatic-to-Diabatic Mixing Angle for B + H$_{2}$ Potential Energy Surfaces Matthew Garvin, David Weeks The 1$^{2}A'$, 2$^{2}A'$, and 1$^{2}A''$ adiabatic potential energy surfaces and associated nonadiabatic coupling terms are calculated at the state-averaged MCSCF/CI level. A line integral through the nonadiabatic coupling terms is used to calculate the adiabatic-to-diabatic mixing angle required to transform from the 1$^{2}A'$ and 2$^{2}A'$ adiabatic basis to a corresponding diabatic basis. When all nonadiabatic coupling terms between all electronic states are considered, the line integral will be path independent. However, for our calculations, we consider only nonadiabatic coupling terms between the 1$^{2}A'$ and 2$^{2}A'$ states and the line integral is therefore path dependent. The path dependence of the line integral is then used to characterize the error introduced by employing a truncated set of adiabatic states. A method for reducing the effect of this error through the use of symmetry derived boundary conditions is discussed. [Preview Abstract] |
Saturday, October 11, 2008 8:24AM - 8:36AM |
C3.00003: Surface effect on the medium-range structure of colloidal and mesoporous silica Gang Chen, Kuangmin Li, Congshang Wan Glasses synthesized by the conventional melt-quenching method and by the sol-gel method do not have exactly the same structure. To understand the medium-range structure of sol-gel derived silica glasses, we have conducted small-angle and wide-angle x-ray scattering experiments on colloidal and mesoporous silica. Effects of particle/pore size and thermal treatment on the first sharp diffraction peak (FSDP) of the silica have been studied. It is found that the FSDP of colloidal silica depends on the particle size as well as thermal treatment. For the mesoporous silica (i.e., MCM-41 and SBA-15), their FSDP differs from that of colloidal silica and shows pore size and/or pore surface morphology dependence. Thermal treatment of mesoporous silica at high temperature causes shrinkage in the pore width and a change in the FSDP. Our study suggests a close relationship between the surface properties and the medium-range structure of sol-gel derived silica glasses. [Preview Abstract] |
Saturday, October 11, 2008 8:36AM - 8:48AM |
C3.00004: Nuclear Magnetic Conduits Rich DeSantis Point charges are not conduits of magnetism. Vacuum gaps between charges prevent superconductivity. Magnetism occurs w/o charge velocity. A changing magnetic field can add magnetism, w/o magnetism's centripetal force adding speed. Voltage is not charge repulsion energy. Passing electrons through a stationary electron's field cannot reduce its field. Passing the external electrons through a charged capacitor's field discharges the capacitor. Chemical bonds extend between atoms. A superconductive magnet contains a superconductive molecule, the length of its wire. Superconductivity dictates that chemical bonding material is non-vacuum and non-point charge. Its unit is an electron/proton fusion called an ABION. Unpaired abions attract all other unpaired abions within or between atoms. Paired abions have reduced attraction for other abions. Helium is inert because its abions are paired. A lithium atom includes an unpaired abion. Superconductive abions are nuclear magnetic conduits. Equality of transference numbers in electrochemistry is evidence of conduits. In fuel cells and semiconductors, paired voltage-induced redox reactions convert lines of abions into conduits. This temporarily converts bulk insulators to conductors. [Preview Abstract] |
Saturday, October 11, 2008 8:48AM - 9:00AM |
C3.00005: Investigating the Diffusive Behavior of HPC with DLS and FPR Ryan McDonough, Kiril Streletzky, Paul Russo Hydroxypropylcellulose (HPC) polymer chains were dissolved in aqueous solution in order to explore their diffusive qualities. Two fundamentally different methods: FPR (Fluorescence Photo-bleaching and Recovery) and DLS (Dynamic Light Scattering) were employed to study the structure and dynamics of HPC chains. FPR requires polymer to be chemically tagged by fluorescent molecules. FPR captures diffusion by establishing a photo-bleached boundary, observing only tagged particles diffusing back into the bleached area, yielding a contrast decay function. DLS auto-correlates scattered light intensity from particles, calculating a decay function which yields information about the self diffusion of particles at chemical equilibrium. An Inverse Laplace Transform Algorithm (CONTIN) and stretch exponential line shape analysis (LSA) quantitatively decomposed spectral decays into diffusion processes or modes. The LSA and CONTIN analysis on the same FPR decay spectra resulted in roughly similar modal distribution and mode intensity results. The modal distributions for FPR and DLS spectra on the same sample have shown consistent dissimilarities which may indicate a comparative limitation and/or sensitivity to a particular range of diffusive speeds or processes. The tag and/or tagging process appear to alter samples in a way that is quantifiable and consistent. The nature of diffusive processes in HPC appears to be complex, but analysis reveals a reproducible picture. [Preview Abstract] |
Saturday, October 11, 2008 9:00AM - 9:12AM |
C3.00006: Production of Singlet Oxygen within a Flow Discharge Matthew Lange, Greg Pitz, Glen Perram The Airborne laser program is an Air Force sponsored program to place a laser on the battle field for use as a tactical weapon. The chemical oxygen iodine laser offers the powers necessary for this weapons application, but it requires significant logistical support. The goal of this current research program is to demonstrate an oxygen-iodine laser with electrical discharge production of singlet oxygen. Optical diagnostics have been applied to microwave and radio frequency discharges within a pure oxygen flow. The O$_{2}$(a) emissions within a discharge are complicated by atomic oxygen emission requiring care in determining gas concentrations from optically measured emissions. Thermal effects also complicate optical emissions. The inclusion of vibrationally excited oxygen as a quencher of the O$_{2}$(a) state appears to be the limiting rate for production of O$_{2}$(a) within the electric discharge conditions studied in this research. [Preview Abstract] |
Saturday, October 11, 2008 9:12AM - 9:24AM |
C3.00007: Temporal Evolution of Arc Emission From Laser REMPI Triggering of Air Spark Gap Jared Miles, Steven Adams A laser-triggering scheme for air spark gap switches was conceived and optical emission during breakdown was analyzed to investigate arc formation. The scheme utilized a pulsed ultraviolet laser to generate resonant enhanced multi-photon ionization (REMPI) within the atmospheric air medium of a spark gap switch. With an applied voltage below the self-breakdown level, the laser-induced pre-ionization initiated avalanche breakdown within the gap and the subsequent triggering of the switch. The pre-ionization was made possible by utilizing resonant 2-photon absorption, exciting O$_2$(X$ ^3\Sigma_g^-$) to the O$_2$(C$ ^3\Pi_g$, v=2) state, followed by ionization with an additional laser photon. The focused laser beam created a pre-ionization channel within the gap establishing the arc path. The spectral and spatial distributions of the emission as a function of time were analyzed to help determine the mechanism for arc formation. Spectral images of the N$_2 $(C $^ 3\Pi_u$ - B $^ 3\Pi_g)$ bands indicated when direct electron impact was the dominant source of ionization, while N$^+$ atomic ion bands indicated that voltage collapse and thermal ionization was occurring. [Preview Abstract] |
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