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Full-Text Articles in Physical Sciences and Mathematics
Molecular Model For Ice Clusters In A Supersaturated Vapor, Barbara N. Hale, P. L. M. Plummer
Molecular Model For Ice Clusters In A Supersaturated Vapor, Barbara N. Hale, P. L. M. Plummer
Physics Faculty Research & Creative Works
A molecular model previously applied to prenucleation water clusters is used to examine ice Ih, embryos. The canonical partition function is evaluated for clusters having from 6 to 64 water molecules. The intermolecular vibrational free energies are extrapolated to clusters containing up to 120 molecules and free energies of formation, nucleation rates, and critical supersaturation ratios are calculated and compared with experiment. For the clusters studied, the ice Ih structure appears to be much less stable at all temperatures than the more spherical clathratelike cluster.
Eikonal Distorted-Wave Calculation For The Excitation Of H By He, Jerry Peacher, Richard H. Shields
Eikonal Distorted-Wave Calculation For The Excitation Of H By He, Jerry Peacher, Richard H. Shields
Physics Faculty Research & Creative Works
The eikonal distorted-wave Born approximation developed recently by Chen, Joachain, and Watson is applied to hydrogen excitation by helium impact in the intermediate-energy range. The differential and total cross sections for the excitation of the hydrogen atom to the 2s, 2p±, or 2p0 state by helium impact are presented. These results are compared to experiment and previous calculations. The differential cross section for the excitation of hydrogen to the 2s state compares well with the experimental data of Thomas and Sauers in shape and slope, but has a discrepancy in magnitude.
Diffusion-Controlled Intrachain Reactions Of Polymers. Ii Results For A Pair Of Terminal Reactive Groups, Gerald Wilemski, Marshall Fixman
Diffusion-Controlled Intrachain Reactions Of Polymers. Ii Results For A Pair Of Terminal Reactive Groups, Gerald Wilemski, Marshall Fixman
Physics Faculty Research & Creative Works
The formulas and results of the preceding paper are used to calculate the rate of reaction between reactive groups attached to the ends of a polymer chain. Extensive numerical calculations have been made for both transient rate processes and steady state luminescence quenching. The results are restricted to chains in dilute solution, in either the free draining or nondraining limits and with no excluded volume forces present. A discussion of the qualitative effects of excluded volume forces on the results is included. The results suggest that experimental studies of these processes may be feasible.
Pb And Bi L-Subshell Ionization Cross-Section Ratios Versus Proton Bombarding Energy From 0.5 To 4 Mev, Don H. Madison, A. B. Baskin, C. E. Busch, Stephen M. Shafroth
Pb And Bi L-Subshell Ionization Cross-Section Ratios Versus Proton Bombarding Energy From 0.5 To 4 Mev, Don H. Madison, A. B. Baskin, C. E. Busch, Stephen M. Shafroth
Physics Faculty Research & Creative Works
Experimental ratios of L-subshell cross sections are given for ionization of lead and bismuth by 0.5-4-MeV-proton bombardment. The ratio of the LII to LI cross sections exhibits a maximum near 1.75 MeV. Individual subshell cross sections are obtained from the experimental ratios and previous total-cross-section data. These subshell ratios and cross sections are compared with the theoretical predictions of the plane-wave Born approximation using nonrelativistic hydrogenic wave functions, of the binary-encounter approximation scaled from Mg K-shell cross sections, and of the binary-encounter approximation scaled from cross sections obtained using L-shell velocity distributions. It was found that both approximations …
Eikonal Approximation Applied To Atom-Atom Excitation At Intermediate Energies: Excitation Of H By H, Richard H. Shields, Jerry Peacher
Eikonal Approximation Applied To Atom-Atom Excitation At Intermediate Energies: Excitation Of H By H, Richard H. Shields, Jerry Peacher
Physics Faculty Research & Creative Works
The eikonal distorted-wave Born approximation (DWBA) developed recently by Chen, Joachain, and Watson is applied to atom-atom excitation in the intermediate energy range. In this paper the excitation of a hydrogen atom to the 2s, 2p±, or 2p0 state by hydrogen impact is considered. Differential cross sections are presented. Total cross sections are presented and compared to previous calculations. It is shown that the eikonal DWBA results for the total cross section approach the two-state distortion-approximation results in the limit of high energy and very-small-angle scattering.
Diffusion-Controlled Intrachain Reactions Of Polymers. I Theory, Gerald Wilemski, Marshall Fixman
Diffusion-Controlled Intrachain Reactions Of Polymers. I Theory, Gerald Wilemski, Marshall Fixman
Physics Faculty Research & Creative Works
A theory of diffusion-controlled intramolecularly catalyzed reactions of polymer chains in dilute solution is formulated. A closure approximation yields a soluble integral equation for (essentially) the transient rate of the reaction. The time dependent solution consists of a sum of simple exponential terms whose coefficients and decay constants can be readily calculated. The theory is also applied to luminescence quenching and ring-chain interconversion.
Structural Strain In Small Prenucleation Water Clusters, Donald E. Hagen
Structural Strain In Small Prenucleation Water Clusters, Donald E. Hagen
Physics Faculty Research & Creative Works
A method is developed for incorporating strain energy into a microphysical treatment of small prenucleation water clusters. The molecules are arranged in a clathrate-cage structure, and this structure is allowed to relax to minimize the strain energy resulting from hydrogen bond stretching and bending. The method is applied to various cluster sizes up to 130 molecules and the results are compared with the classical liquid drop model. The effect of anharmonic terms in the interaction is included.
Dispersion Curves For Surface Electromagnetic Waves With Damping, Ralph William Alexander, G. S. Kovener, Robert John Bell
Dispersion Curves For Surface Electromagnetic Waves With Damping, Ralph William Alexander, G. S. Kovener, Robert John Bell
Physics Faculty Research & Creative Works
The Recent Observation of Back bending in the Dispersion Curves of Surface Plasmons on Silver Can Be Explained by Use of Fresnel's Equations. in the Presence of Damping, the Results of Attenuated-Total-Reflection Measurements Can Be Displayed as Dispersion Curves Either with or Without Back bending. the Measurements for Silver with Back Bending Are Expected for Experiments in Which the Frequency is Fixed, and the Propagation Constant (Or Angle of Incidence) is Swept. © 1974 the American Physical Society.
Cross Sections For Photoionization Of The 6²P-Fine Structure Levels Of Cesium, John Daniel Jones
Cross Sections For Photoionization Of The 6²P-Fine Structure Levels Of Cesium, John Daniel Jones
Doctoral Dissertations
"The cross sections for photoionization of excited cesium from the 62P3/2- and 6²P1/2-fine structure levels have been measured using a triple crossed-beam apparatus. Two photon beams, one for excitation and one for ionization, impinge upon an atomic beam and produce ions at the point of intersection. The relative cross section is determined from a knowledge of the ion count rate and the relative photon flux of the ionization light. The results are normalized to available theoretical calculations and compared with recombination measurements in cesium plasmas. The present cross sections are found to decrease with …
Surface Electromagnetic Waves With Damping I. Isotropic Media Ii. Anisotropic Media, Gary Shannon Kovener
Surface Electromagnetic Waves With Damping I. Isotropic Media Ii. Anisotropic Media, Gary Shannon Kovener
Doctoral Dissertations
Paper 1: “Surface electromagnetic wave (SEW) dispersion curves are usually calculated using a simple equation derived from Maxwell’s equations and boundary conditions. When complex dielectric functions are used for the two media, the component of the propagation vector along the surface kx becomes infinite as the frequency ω approaches the surface polariton frequency ωs if ω is considered complex and kx real. On the other hand, if kx is considered complex and ω real, the dispersion curves bend back toward smaller kx as ω approaches ωs. We have previously demonstrated that both types …
On The Lambda Transition In Solid Orthohydrogen, Harry A. Brown
On The Lambda Transition In Solid Orthohydrogen, Harry A. Brown
Physics Faculty Research & Creative Works
No abstract provided.
Optical Pumping In A Flowing Helium Afterglow With Additive Metal Impurity Atoms, Laird D. Schearer
Optical Pumping In A Flowing Helium Afterglow With Additive Metal Impurity Atoms, Laird D. Schearer
Physics Faculty Research & Creative Works
It is demonstrated that in a Penning collision of optically oriented metastable helium atoms with an impurity metal atom such as barium, both the longitudinal and transverse components of spin angular momentum are conserved. This results in a polarization of the ion which may be detected by optical emission in the case of excited ion levels or absorption for the ground states. A series of experiments is described which demonstrates the spin dependence of the Penning-collision process. The magnetic resonance of excited-state ions may be observed directly; from the resonance-linewidth radiative lifetimes may be measured. © 1974 The American Physical …
Fresnel Drag In Uniformly Moving Media, William F. Parks, J. T. Dowell
Fresnel Drag In Uniformly Moving Media, William F. Parks, J. T. Dowell
Physics Faculty Research & Creative Works
A general first-order formula is derived for the Fresnel-drag effect in a uniformly moving medium with a plane surface. The two classical equations due to Lorentz and Laub are shown to be special cases corresponding to different experimental arrangements. The recent experiment of Bilger and Zavodny on Fresnel drag in a ring laser is discussed. © 1974 The American Physical Society.
Measurements Of The Average Electric Dipole Polarizabilities Of The Alkali Dimers, Robert W. Molof, Thomas M. Miller, Henry L. Schwartz, Benjamin Bederson, John T. Park
Measurements Of The Average Electric Dipole Polarizabilities Of The Alkali Dimers, Robert W. Molof, Thomas M. Miller, Henry L. Schwartz, Benjamin Bederson, John T. Park
Physics Faculty Research & Creative Works
The average electric dipole polarizabilities of the homonuclear alkali dimers have been measured in an electric deflection experiment. The molecular results are normalized to the corresponding atomic polarizabilities by comparing deflections of atomic and molecular alkali beams passing through an inhomogenous electrostatic field. The average polarizabilities in units of 10-24 cm3 are: Li2(990°K), 34±3; Na2(736°K), 30±3; K2(569°K), 61±5; Rb2(534°K), 68±7; Cs2(515°K), 91±7. Copyright © 1974 American Institute of Physics.
Charge Transfer Between O Ions And O2 Molecules In The Ground State And Singlet Delta Excited State, R. F. Mathis, William R. Snow
Charge Transfer Between O Ions And O2 Molecules In The Ground State And Singlet Delta Excited State, R. F. Mathis, William R. Snow
Physics Faculty Research & Creative Works
A crossed-beam apparatus has been used to study charge transfer between O- ions and O2 molecules in the ground state and in the metastable, singlet delta, excited state. The energy of the incident ions ranged from 10 to 10000 eV. The cross section for charge transfer between O - and ground state O2 was found to have a maximum of 7.8X10-16 cm2 at about 5 keV. At the lower energies there is good agreement with the previous measurements of Snow et al. and Rutherford and Turner who also used crossed beam techniques. The cross section for charge transfer between O- …
Evaluation Of Model For The Contributin Of Phonon-Induced Tunneling To Donor Esr Spectral Narrowing In Germanium, David L. Meier, William F. Parks, Edward Boyd Hale
Evaluation Of Model For The Contributin Of Phonon-Induced Tunneling To Donor Esr Spectral Narrowing In Germanium, David L. Meier, William F. Parks, Edward Boyd Hale
Physics Faculty Research & Creative Works
The model commonly assumed to explain the narrowing of the ESR spectra of donor impurities in germanium is examined in detail. This model combines the Anderson line-narrowing theory with the Miller and Abrahams theory for the phonon-induced tunneling (hopping) of an electron between impurities. The predictions of this model are found to be in drastic disagreement with experimental results now available. It is shown that the narrowed linewidth should depend strongly on donor concentration, acceptor concentration, and temperature. Future spin-resonance experiments in highly compensated samples may show the effects of hopping, but no evidence now exists which indicates that hopping …
Double Reflection Dips - From Grating Ruled Semiconductors, Le-Fu Teng
Double Reflection Dips - From Grating Ruled Semiconductors, Le-Fu Teng
Doctoral Dissertations
"The double dips, previously observed by Fischer, Anderson, et al., which appeared in the reflection spectra of grating surfaces on the Te-doped semiconductors GaAs and InSb around the plasmon and phonon frequencies have been measured in more detail. In the plasmon region, several possible explanations of the phenomenon are discussed. A simple equation checked with the rigorous theory is proposed and is shown to fit the data well. In the phonon region, the extra dip is calculated and identified as being caused by surface phonons"--Abstract, page ii.