Energy of the quasi-free electron in atomic and molecular fluids
Item
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Title
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Energy of the quasi-free electron in atomic and molecular fluids
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Identifier
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d_2009_2013:f7f511c99ca5:10510
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identifier
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10601
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Creator
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Shi, Xianbo,
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Contributor
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Cherice M. Evans
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Date
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2010
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physical chemistry | Atomic physics | Molecular physics | electron mobility | field ionization | quasi-free electron energy | supercritical fluid | Wigner-Seitz model
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Abstract
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The ability to predict accurately the density dependent evolution of the conduction band energy of insulators has applications in the optimization of solvent choice and thermodynamic conditions for chemical reactions. However, directly investigating density dependent changes in the conduction band is experimentally difficult. Therefore, we have used field ionization of high- n dopant Rydberg states to determine the perturber induced shift of the dopant ionization energy Delta(rhoP), where rho P is the perturber number density. Appropriate modeling allows the minimum of the conduction band energy V0(rhoP) to be extracted from Delta(rhoP). Field ionization requires the measurement of photoionization spectra of a dopant at two different electric field strengths. Thus, in this study, photoionization spectra of various dopants (i.e., CH3I, C2H5I, N,N-dimethylanaline, trimethylamine and triethylamine) were obtained under different electric field strengths in atomic (i.e., Ar, Kr, and Xe) and molecular (i.e., CH4 and C2H6) perturbers from low density to the density of the triple point liquid, at non-critical temperatures and on an isotherm near the perturber critical isotherm.;At low perturber number density, a temperature dependence was observed in Delta(rhoP), with |Delta(rhoP)| increasing as the temperature decreases. This observation contradicts the prediction of the Fermi-Alekseev-Sobel'man model. Within the local Wigner-Seitz model developed by our group, the temperature behavior at low density arises from the ensemble average ion/perturber polarization energy P +(rhoP) and is caused by variations in the dopant/perturber radial distribution function. Moreover, a striking critical point effect in V0(rhoP) was observed in all of the perturbers investigated. This critical point effect is explained by the dramatic increase in the local density around a perturber particle near the critical point of the perturber. This local density increase, caused by an increase in the correlation length of the perturber, acts to confine the quasi-free electron, thereby increasing its kinetic energy. Various intermolecular potentials and integral methods necessary to calculate the radial distribution functions were studied and tested in order to achieve the best fit to the experimental Delta(rho P) in molecular perturbers.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Chemistry
