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Faculty Publications, Department of Physics and Astronomy

Articles 151 - 174 of 174

Full-Text Articles in Physics

Optical And Magneto-Optical Constants Of Mnpt3, K. W. Wierman, J. N. Hilfiker, R. F. Sabiryanov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam Feb 1997

Optical And Magneto-Optical Constants Of Mnpt3, K. W. Wierman, J. N. Hilfiker, R. F. Sabiryanov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam

Faculty Publications, Department of Physics and Astronomy

Optically thick films of MnPt3 were deposited on quartz using dc magnetron sputtering. The films were covered with an SiOx protective overcoat and annealed in vacuum at 850 °C for 1 h to form the crystalline L12 (Cu3Au) cubic structure. These films have a high degree of long-range order and are highly textured with the (111) axis along the film normal. Variable angle spectroscopic ellipsometry measurements were taken over the spectral range of 1.2–4.2 eV to determine the optical constants of both MnPt3 and the SiOx overcoat. Spectroscopic magneto-optic ...


Biographical Sketch Of M. Eugene Rudd, Robert Katz, Duane H. Jaecks Oct 1996

Biographical Sketch Of M. Eugene Rudd, Robert Katz, Duane H. Jaecks

Faculty Publications, Department of Physics and Astronomy

Dr. Rudd's research in atomic collision physics has been characterized by originality and thoroughness. He has written review articles and chapters in the Encyclopedia of Physics - and elsewhere, and is a co-author on a book on atomic collisions. He has published more than 75 refereed research papers, many of which were of seminal importance. He was the first to study systematically the dependence of the probability for electron emission in ion-atom collisions on the incident ion's energy, and on the ejected electron's energy and angle of emission. In 1964 he made the first experimental observation of doubly ...


Radial Dose Distributions In The Delta-Ray Theory Of Track Structure, Francis A. Cucinotta, Robert Katz, John W. Wilson, Rajendra R. Dubey Oct 1996

Radial Dose Distributions In The Delta-Ray Theory Of Track Structure, Francis A. Cucinotta, Robert Katz, John W. Wilson, Rajendra R. Dubey

Faculty Publications, Department of Physics and Astronomy

The radial dose distribution from delta rays, fundamental to the delta ray theory of track structure, is recalculated. We now include the model of Rudd for the secondary electron spectrum in proton collisions. We include the effects of electron transmission through matter and the angular dependence of secondary electron emission. Empirical formulas for electron range versus electron energy are intercompared in a wide variety of materials in order to extend the track structure theory to arbitrary media. Radial dose calculations for carbon, water, silicon, and gold are discussed. As in the past, effective charge is used to scale to heavier ...


Supermassive Binaries And Extragalactic Jets, C. Martin Gaskell May 1996

Supermassive Binaries And Extragalactic Jets, C. Martin Gaskell

Faculty Publications, Department of Physics and Astronomy

Some quasars show Doppler shifted broad emission line peaks. I give new statistics of the occurrence of these peaks and show that, while the most spectacular cases are in quasars with strong jets inclined to the line of sight, they are also almost as common in radio-quiet quasars. Theories of the origin of the peaks are reviewed and it is argued that the displaced peaks are most likely produced by supermassive binaries. 3C 390.3 shows precisely the change in radial velocity predicted by the supermassive binary model. The separations of the peaks in 3C 390.3-type objects are consistent ...


Magnetic And Magneto-Optical Properties Of MnXCubi ( X =0.75 - 3.5 ) Films, Jian Chen, K. Wierman, Roger D. Kirby, David J. Sellmyer Nov 1995

Magnetic And Magneto-Optical Properties Of MnXCubi ( X =0.75 - 3.5 ) Films, Jian Chen, K. Wierman, Roger D. Kirby, David J. Sellmyer

Faculty Publications, Department of Physics and Astronomy

Magnetic and magneto-optical properties of MnxCuBi ( x = 0.75 - 3.5) thin films are presented. With increasing Mn concentration x, the perpendicular anisotropy constant (Ku the remanence squareness (S = Mr/Ms) and the coercivity (Hc)the perpendicular hysteresis loop increase. Remanence squareness as high as 0.95 has been obtained. Kerr rotation (θk) and ellipticity (ηk) spectra from all samples measured from substrate side are similar, with θk exhibiting a broad peak in the blue wavelength region with maximum Kerr rotation up to 0.7 degrees.


Magnetic And Magneto-Optical Properties Of MnXCubi ( X =0.75 - 3.5 ) Films†, Jian Chen, K. Wierman, Roger D. Kirby, David J. Sellmyer Nov 1995

Magnetic And Magneto-Optical Properties Of MnXCubi ( X =0.75 - 3.5 ) Films†, Jian Chen, K. Wierman, Roger D. Kirby, David J. Sellmyer

Faculty Publications, Department of Physics and Astronomy

Abstract - Magnetic and magneto-optical properties of MnxCuBi ( x = 0.75 - 3.5) thin films are presented. With increasing Mn concentration x, the perpendicular anisotropy constant (Ku), the remanence squareness (S = Mr/Ms) and the coercivity (Hc ), of the perpendicular hysteresis loop increase. Remanence squareness as high as 0.95 has been obtained. Kerr rotation (Өk) and ellipticity (ηk) spectra from all samples measured from substrate side are similar, with Өk exhibiting a broad peak in the blue wavelength region with maximum Kerr rotation up to 0.7 degrees.


Small Polarons And The Electronic Properties Of Mo2S3, Adilgiry A. Kusov, Roger D. Kirby Dec 1994

Small Polarons And The Electronic Properties Of Mo2S3, Adilgiry A. Kusov, Roger D. Kirby

Faculty Publications, Department of Physics and Astronomy

We investigate the small-polaron mechanism as a possible explanation of electrical-conduction and electrical-noise properties of the linear chain material Mo2S3. Experimental conductivity and noise data obtained in earlier papers [Phys. Rev. B 38, 3973 (1988); Phys. Rev. B 39, 5139 (1989)] are analyzed in terms of a small-polaron mechanism and double-well potential model. We interpret the observed electronic properties in terms of kinetic equations describing the interaction of free carriers with fluctuations of density of the lattice. Appropriate kinetics equations to describe this interaction, which leads to small-polaron formation, are derived. These equations are found to explain ...


Magnetization Reversal In Nanoscale Magnetic Films With Perpendicular Anistropy, Roger D. Kirby, J.X. Shen, Robert J. Hardy, David J. Sellmyer Apr 1994

Magnetization Reversal In Nanoscale Magnetic Films With Perpendicular Anistropy, Roger D. Kirby, J.X. Shen, Robert J. Hardy, David J. Sellmyer

Faculty Publications, Department of Physics and Astronomy

We present experimental results on magnetization reversal for a class of nanoscale magnetic films with perpendicular magnetic anistropy and develop a model that describes a variety of related experiments. In this model the sample is divided into identical single domain cells that interact through dipolar fields and a nearest-neighbor domain-wall interaction. Monte Carlo simulations give insights into the relationship between macroscopic magnetic parameters and the reversal behavior and demonstrate the important role that thermal activation plays in the reversal process.


Slowing Of 85Rb Atoms With Isotropic Light, Herman Batelaan, S. Padua, D. H. Yang, C. Xie, R. Gupta, Harold Metcalf Mar 1994

Slowing Of 85Rb Atoms With Isotropic Light, Herman Batelaan, S. Padua, D. H. Yang, C. Xie, R. Gupta, Harold Metcalf

Faculty Publications, Department of Physics and Astronomy

We have demonstrated the slowing of a rubidium atomic beam by isotropic monochromatic light. The results agree with a model calculation, thus allowing its use for designing a practical isotropic light slower. The large hyperfine splittings of rubidium lead to natural multifrequency slowing, which is also included in our model.


Steps Toward Determinaton Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. V. Variability Of The Ultraviolet Continuum And Emission Lines Of Ngc 3783, G. A. Reichert, P. M. Rodriguez-Pascual, D. Alloin, J. Clavel, D. Michael Crenshaw, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, W. Wamsteker, A. Altamore, B. Altieri, K. S.J. Anderson, J. H. Blackwell Jr,, C. Boisson, N. Brosch, T. E. Carone, M. Dietrich, M. N. England, I. N. Evans, A. V. Filippenko, C. Martin Gaskell, M. Goad, P. M. Gondhalekar., K. Horne, D. Kazanas, W. Kol Latschny, A. P. Koratkar, Kirk T. Koristag, G. M. Macalpine, D. Maoz, T. Mazeh, B. Mccollum, H. Richard Miller, C. Mendes De Oliveira, Paul T. O'Brien, M. G. Pastoriza, D. Pelat, E. Perez, G. C. Perola, Richard William Pogge, R. L. Ptak, M. C. Recondo-Gonzalez, J. Rodriguez-Espinosa, E. I. Rosenblatt, A. C. Sadun, M . Santos-Lleo, J. C. Shields, C. R. Shrader, J. M. Shull, S. M. Simkin, M. L. Sitko, M. A.J Snuders, L. S. Sparke, G. M. Stirpe, R. Stoner, T. . Storchi-Bergm, W. H. Sun, T. F. Wang, W. F. Welsh, R. J. White, C. Winge, W. Zhen Jan 1994

Steps Toward Determinaton Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. V. Variability Of The Ultraviolet Continuum And Emission Lines Of Ngc 3783, G. A. Reichert, P. M. Rodriguez-Pascual, D. Alloin, J. Clavel, D. Michael Crenshaw, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, W. Wamsteker, A. Altamore, B. Altieri, K. S.J. Anderson, J. H. Blackwell Jr,, C. Boisson, N. Brosch, T. E. Carone, M. Dietrich, M. N. England, I. N. Evans, A. V. Filippenko, C. Martin Gaskell, M. Goad, P. M. Gondhalekar., K. Horne, D. Kazanas, W. Kol Latschny, A. P. Koratkar, Kirk T. Koristag, G. M. Macalpine, D. Maoz, T. Mazeh, B. Mccollum, H. Richard Miller, C. Mendes De Oliveira, Paul T. O'Brien, M. G. Pastoriza, D. Pelat, E. Perez, G. C. Perola, Richard William Pogge, R. L. Ptak, M. C. Recondo-Gonzalez, J. Rodriguez-Espinosa, E. I. Rosenblatt, A. C. Sadun, M . Santos-Lleo, J. C. Shields, C. R. Shrader, J. M. Shull, S. M. Simkin, M. L. Sitko, M. A.J Snuders, L. S. Sparke, G. M. Stirpe, R. Stoner, T. . Storchi-Bergm, W. H. Sun, T. F. Wang, W. F. Welsh, R. J. White, C. Winge, W. Zhen

Faculty Publications, Department of Physics and Astronomy

We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or "dips," the first lasting ≤20 days and the second ≤ 4 days, with additional episodes of relatively rapid flickering ...


Simplest Atomic System For Sub-Doppler Laser Cooling, R. Gupta, S. Padua, C. Xie, Herman Batelaan, Harold Metcalf Jan 1994

Simplest Atomic System For Sub-Doppler Laser Cooling, R. Gupta, S. Padua, C. Xie, Herman Batelaan, Harold Metcalf

Faculty Publications, Department of Physics and Astronomy

Sub-Doppler laser cooling requires optical pumping among differently light-shifted ground-state sublevels. We describe a study of the simplest possible angular-momentum configuration that permits all sub-Doppler cooling phenomena. The Jg = 1 ⟹ Je = 0 angular-momentum configuration shows recoil-limited cooling in the two most well-known types of polarization gradient, magnetically induced laser cooling, velocity-selective resonances, transient cooling, and velocity-selective population trapping.


Linear Dichroism In Photoemission From Oriented Molecules, N. A. Cherepkov, G. Schönhense Oct 1993

Linear Dichroism In Photoemission From Oriented Molecules, N. A. Cherepkov, G. Schönhense

Faculty Publications, Department of Physics and Astronomy

It is shown that oriented molecules reveal both Linear Dichroism (LD) and Linear Dichroism in the Angular Distribution (LDAD) of photoelectrons, which means a difference between photoelectron currents ejected at a definite angle by linearly polarized light of two mutually perpendicular polarizations. Measurements of LD and LDAD enable one to investigate the orientation of molecules and to make an essential step towards the complete quantum-mechanical experiment. As an example, LDAD in a model case of oriented heteronuclear diatomic molecules is presented.


Mixed-Crystal Lattice Dynamics Of HfXTi1-XSe2, Vanvilai Katkanant, Roger D. Kirby Jul 1989

Mixed-Crystal Lattice Dynamics Of HfXTi1-XSe2, Vanvilai Katkanant, Roger D. Kirby

Faculty Publications, Department of Physics and Astronomy

The first-order Raman spectra of the mixed-crystal layered compound HfxTi1-xSe2 have been studied over the whole range of concentrations 0≤x≤1. Both pure compounds, TiSe2 and HfSe2, have the CdI2 structure and so have two Raman-active phonons of A1g phonon is at about 205 cm -1. As x is decreased from 1.0, a new Raman peak, of A1g symmetry, appears near 180 cm -1. As x is decreased further, this peak shifts smoothly upwards in frequency, until it finally merges (by x=0.05) with the pure TiSe ...


Metastable Conduction States In Mo2S3: Conductivity Fluctuations, R.L. Fagerquist, Roger D. Kirby, Edgar A. Pearlstein Mar 1989

Metastable Conduction States In Mo2S3: Conductivity Fluctuations, R.L. Fagerquist, Roger D. Kirby, Edgar A. Pearlstein

Faculty Publications, Department of Physics and Astronomy

In this paper, we present the results of measurements of the frequency and temperature dependences of the electrical noise in Mo2S3. It will be seen that the frequency dependence of the noise is completely consistent with the double-well potential model for the carriers in Mo2S3 introduced in an earlier paper [Phys. Rev. B 38, 3973 (1988)]. In the earlier paper, we showed that at temperatures below 145 K, the carriers in Mo2S3 could exist in either a weakly conducting ground state or a relatively highly conducting metastable state. The conductivity behavior ...


Using Nuclear Resonance Excitation To Observe United Atoms In Symmetric Ion-Atom Collisions, James M. Feagin, Ladislov Kocbach Apr 1983

Using Nuclear Resonance Excitation To Observe United Atoms In Symmetric Ion-Atom Collisions, James M. Feagin, Ladislov Kocbach

Faculty Publications, Department of Physics and Astronomy

We consider nuclear resonance excitation as a means to observe the distribution of united-atom orbitals in symmetric ion-atom collisions. We develop this possibility with the application of a two-state adiabatic model to an analysis of a 8Be nuclear resonance experiment. To test our model, and to provide a more direct determination of the nuclear resonance width, we propose that the 8Be experiment be repeated with metastable helium targets.


The Light Curves Of Rr Lyrae Field Stars, Norman R. Simon, Terry J. Teays Jan 1982

The Light Curves Of Rr Lyrae Field Stars, Norman R. Simon, Terry J. Teays

Faculty Publications, Department of Physics and Astronomy

Fourier decompositions have been made of the light curves of a large sample of RR Lyrae field stars. The coefficients have been tabulated. Following the scheme of an earlier investigation of classical Cepheids, certain combinations of the low-order coefficients - φ21, R21, and φ31 - are plotted against period. The Bailey-type c pulsators stand out from the type ab stars, particularly on the R21 plot which is found to be a more sensitive discriminator of Bailey type than is the traditionally employed amplitude-period diagram. We compare the RR Lyrae plots of φ21, R21, and φ31 ...


The Coma/A1367 Supercluster And Its Environs, Stephen A. Gregory, Laird A. Thompson Jan 1978

The Coma/A1367 Supercluster And Its Environs, Stephen A. Gregory, Laird A. Thompson

Faculty Publications, Department of Physics and Astronomy

The three-dimensional galaxy distribution in the region of space surrounding the two rich clusters Coma and A1367 is analyzed by using a nearly complete redshift sample of 238 galaxies with mp < 15.0 in a 260 degree2 region of the sky; 44 of these redshifts are reported here for the first time. We find that the two clusters are enveloped in a common supercluster which also contains four groups and a population of isolated galaxies. The least dense portions of the Coma/A1367 supercluster have a density which is approximately 6 times that of the Local Supercluster in the regions of our own Galaxy ...


Evolved Contact Systems Of Spectral Type A: Au Puppis, V535 Arae, And V1073 Cygni, Kam-Ching Leung, Donald P. Schneider Jan 1978

Evolved Contact Systems Of Spectral Type A: Au Puppis, V535 Arae, And V1073 Cygni, Kam-Ching Leung, Donald P. Schneider

Faculty Publications, Department of Physics and Astronomy

The photoelectric observations of AU Pup, V535 Ara, and V1073 Cyg were reanalyzed with Wilson and Devinney's approach. All three systems are found to be contact configurations. AU Pup has an unusually large degree of overcontact, 72%. V1073 Cyg is found to be an evolved contact system since the radius of the primary is twice that of a zero-age main-sequence star of corresponding mass. All three systems are found to be evolved according to their locations in the period-spectral-type diagram. Improved photometric parameters are reported for all three systems.


Eclipsing Systems In Star Structures. Iii. Early-Type Contact System Bh Centauri, Kam-Ching Leung, Donald P. Schneider Jan 1977

Eclipsing Systems In Star Structures. Iii. Early-Type Contact System Bh Centauri, Kam-Ching Leung, Donald P. Schneider

Faculty Publications, Department of Physics and Astronomy

Close to 1000 photoelectric observations of BH Cen in the yellow, blue, and ultraviolet regions were analyzed. The period found was 0.791616 days. The depths of minima were about equal, and were more than 1 magnitude! A photometric solution was derived with the Wilson and Devinney model. The binary is an overcontact system with primary and secondary masses equal to 10 M?. Based on its membership in IC 2944 and the size of the primary radius, BH Cen may be another example of a zero-age contact system.


H I In Early-Type Galaxies. Ii. Mass Loss And Galactic Winds, S. M. Faber, J. S. Gallagher Jan 1976

H I In Early-Type Galaxies. Ii. Mass Loss And Galactic Winds, S. M. Faber, J. S. Gallagher

Faculty Publications, Department of Physics and Astronomy

Implications of observed upper limits to the neutral hydrogen content of E and SO galaxies from Paper I are discussed. If gas shed by dying stars is completely retained by these galaxies and exists as H I, these upper limits will be exceeded in only 109 yr for E's and SO's and in only 2 x 108 yr for NGC 4472. Evidently, gas either is hidden in some undetectable form or is removed from the interstellar medium completely.


Shell Source Burning Stars With Highly Condensed Cores, S. Refsdal, A. Weigert Jan 1970

Shell Source Burning Stars With Highly Condensed Cores, S. Refsdal, A. Weigert

Faculty Publications, Department of Physics and Astronomy

Simple analytical relations are derived - similar to the homology relations for homogeneous stam - which describe the behaviour of shell source burning models with highly condensed cores. Many features which are known from evolutionary calculations (and partly &om observations) of such stars can be understood as coming essentially from the increase of the mass M6 of the core.


Specificity Of The London-Eisenschitz Wang Force*, Jerrold M. Yos, William L. Bade, Herbert Jehle Jan 1957

Specificity Of The London-Eisenschitz Wang Force*, Jerrold M. Yos, William L. Bade, Herbert Jehle

Faculty Publications, Department of Physics and Astronomy

The London force between macromolecules immersed in a liquid medium has an interesting property which may be of biological significance. For the purpose of formulating the London interaction, one may represent each macromolecule by a set of electric dipole oscillators of specified polarizability, frequency, and orientation. To consider the simplest case, one may study macromolecules of globular form not in direct contact with each other. (They might be separated by Debyeiuckel- Onsager atmospheres made up of molecules from the medium; then the equilibrium distance between the macromolecules would be regulated by concentration changes in the ionic medium.)' Such a geometrical ...


Specificity Of Intermolecular Forces Due To Quantummechanical And Thermal Charge Fluctuations*, Herbert Jehle Jan 1957

Specificity Of Intermolecular Forces Due To Quantummechanical And Thermal Charge Fluctuations*, Herbert Jehle

Faculty Publications, Department of Physics and Astronomy

The preceding note1 (Paper I) developed the theory of the specificity of some intermolecular forces: the forces due to fluctuations of electric charge distribution in and over the interacting molecules. It was found that for a mixture of molecules in a liquid medium these forces cause a rearrangement of the molecules, so that molecules which have the same distribution of oscillator polarizabilities and oscillator orientations over the frequency spectrum tend to associate. This means that like molecules tend to become nearest neighbors. For that reason it was said that there is specific attraction between identical molecules.


Iii. Phase Change By Reflection – Primarily In The Ultra-Violet, Oliver Gish Apr 1914

Iii. Phase Change By Reflection – Primarily In The Ultra-Violet, Oliver Gish

Faculty Publications, Department of Physics and Astronomy

The first quantitative investigation of absolute phase change was made by Quinckel in 1872. This was followed by that of Wernicke, Wiener, Glan, Hennig, Drude, Koenigsberger and Bender. All these investigations were confined to the visible spectrum except that of Koenigsberger and Bender, who, in addition, measured for a few substances the phase change in the infra-red. So far no measurements of this phenomenon have been made in the ultra-violet.