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Full-Text Articles in Physics

Stopping Power Of Matter For Alpha Particles At Extreme Relativistic Energies, P.T. Leung, M. L. Rustgi, J. E. Turner Dec 1980

Stopping Power Of Matter For Alpha Particles At Extreme Relativistic Energies, P.T. Leung, M. L. Rustgi, J. E. Turner

Physics Faculty Publications and Presentations

The stopping power of matter for alpha particles at extreme relativistic energies has been calculated by incorporating the charge form factor. A table is presented for aluminum, copper, and lead. It is found that at the highest energies considered, inclusion of form factor reduces the mass stopping power by about 6-8% in comparison with that predicted by Bethe's relativistic formula.


Direct Observation Of The Behavior Of The Heavy Single Atoms On Amorphous Carbon Substrates, Mark Utlaut Nov 1980

Direct Observation Of The Behavior Of The Heavy Single Atoms On Amorphous Carbon Substrates, Mark Utlaut

Physics Faculty Publications and Presentations

Using a scanning transmission electron microscope it is possible, by directly imaging single atoms, to investigate the motion and distribution of heavy (high-Z) atoms deposited on the surfaces of thin low-Z films. In this study, the heavy atoms U, Pt, Au, In, Cd, Ag, and Pd were deposited on 15-Å-thick amorphous carbon substrates. It is found that adatom motion is strongly dependent upon local substrate structure and adatom species. Diffusion coefficients and activation energies for single atoms, as well as dimers, trimers, etc., have been obtained by directly measuring the motion of the atoms. Pair-density and nearest-neighbor distributions were measured ...


Dielectric Saturation In Dipolar Fluids. I. The Single-Molecule Distribution Function, John D. Ramshaw Nov 1980

Dielectric Saturation In Dipolar Fluids. I. The Single-Molecule Distribution Function, John D. Ramshaw

Physics Faculty Publications and Presentations

The functional-derivative formalism is used to investigate the form of the equilibrium single-molecule distribution function n(1) in a finite fluid system of rigid polar molecules subjected to a strong external electric field that varies slowly with position. The investigation is based on the assumption that the long-range asymptotic behavior of the direct correlation function is independent of the external field, and is hence the same as in the unperturbed fluid. This assumption implies that n(1) has the form of a single-molecule Boltzmann factor in which the interaction energy is that of a deformable quasidipole with the local Lorentz ...


Debye–Hückel Theory For Particles Of Arbitrary Electrical Structure, John D. Ramshaw Oct 1980

Debye–Hückel Theory For Particles Of Arbitrary Electrical Structure, John D. Ramshaw

Physics Faculty Publications and Presentations

Classical linearized Debye–Hückel theory is formulated for a finite fluid system, of arbitrary shape, composed of rigid particles with arbitrary internal electrical structure. The multipole description is eschewed in favor of the more basic description of a particle in terms of its charge density function. This function is left arbitrary, so the particles may be charged or neutral, polar or nonpolar, etc. The theory implies that the direct correlation function c(12)=−v(12)/k T, where v(12) is the Coulomb interaction energy between the charge densities of particles 1 and 2. In the case of uncharged polar ...


Partial Chemical Equilibrium In Fluid Dynamics, John D. Ramshaw Apr 1980

Partial Chemical Equilibrium In Fluid Dynamics, John D. Ramshaw

Physics Faculty Publications and Presentations

An analysis is given for the flow of a multicomponent fluid in which an arbitrary number of chemical reactions may occur, some of which are in equilibrium while the others proceed kinetically. The primitive equations describing this situation are inconvenient to use because the progress rates ω [subscript s] for the equilibrium reactions are determined implicitly by the associated equilibrium constraint conditions. Two alternative equivalent equation systems that are more pleasant to deal with are derived. In the first system, the ω [subscript s] are eliminated by replacing the transport equations for the chemical species involved in the equilibrium reactions ...


Critical Exponents To Order Ε³ For Φ³ Models Of Critical Phenomena In 6-Ε Dimensions, O. F. De Alcantara Bonfim, J. E. Kirkham, A. J. Mckane Jan 1980

Critical Exponents To Order Ε³ For Φ³ Models Of Critical Phenomena In 6-Ε Dimensions, O. F. De Alcantara Bonfim, J. E. Kirkham, A. J. Mckane

Physics Faculty Publications and Presentations

The authors study scalar field theories for which the interaction term of the Hamiltonian is cubic in the fields. They indicate the circumstances for which field theory models of this type represent continuous phase transitions. The renormalisation group functions for these models are presented up to, and including, three-loop contributions, giving critical exponents to order epsilon 3in 6- epsilon dimensions. The exponent sigma which characterises the Yang-Lee edge singularity is given explicitly to this order.