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Full-Text Articles in Physics
Improving Physics Teaching, Robert Fuller
Improving Physics Teaching, Robert Fuller
Robert G. Fuller Publications
I began this editorial with a desire to take up battle against the recent ills of physics teaching. I paused to peruse the AAPT reprint book, 50 Years on Teaching Physics, edited by Melba Phillips.
Trends In The Theory Of Atomic Photoionization, Anthony F. Starace
Trends In The Theory Of Atomic Photoionization, Anthony F. Starace
Anthony F. Starace Publications
For VUV photon energies, detailed theoretical understanding of the photoionization process has been achieved for the case of a single electron ionized from one of the outer subshells of a closed-shell atom. This understanding is based qualitatively upon a few properties of realistic atomic central potentials and quantitatively upon a few distinct types of electronic interactions known generically as particle-hole interactions. Current theoretical research is mainly directed at understanding a broader class of atomic photoionization phenomena involving, e.g., open-shell atoms, electronic interactions not of the particle-hole class, real two-electron processes, and external electric and magnetic fields.
Computed Cross Sections For Electron Transfer In Ba+ + Ba+ Collisions , Stanley J. Sramek, J.H. Macek, Gordon A. Gallup
Computed Cross Sections For Electron Transfer In Ba+ + Ba+ Collisions , Stanley J. Sramek, J.H. Macek, Gordon A. Gallup
Gordon Gallup Publications
Cross sections have been computed for the electron-transfer process Ba++Ba+→Ba+Ba++, for collision energies ranging from 25 to 500 keV. The straight-line classical-trajectory method has been used, with basis functions obtained by the multiconfiguration valence-bond method. Several numerical procedures applicable to future treatments of similar large systems were developed. The maximum cross-section value is found to be around 27π a02 (2.4 × 10-15 cm2), and occurs near collision energy 500 keV. The system's transient behavior has also been studied in detail during the collision, and it has been found that …
Orientation And Alignment Of The 3P 1P And 4D 1D Levels Of Neutral Helium, R. M. Schectman, R. D. Hight, S. T. Chen, L. J. Curtis, H. G. Berry, Timothy J. Gay, R. Deserio
Orientation And Alignment Of The 3P 1P And 4D 1D Levels Of Neutral Helium, R. M. Schectman, R. D. Hight, S. T. Chen, L. J. Curtis, H. G. Berry, Timothy J. Gay, R. Deserio
Timothy J. Gay Publications
The alignment and orientation produced by the tilted-foil excitation of He was studied for a wide range of foil tilt angles and outgoing-atom velocities. In particular, two quantum states of different orbital angular momentum (3p 1P and 4d 1D) were investigated and the results were compared with a number of previously proposed models.
Photoionization Cross Section For He In The Hyperspherical Coordinate Method, Donald L. Miller, Anthony F. Starace
Photoionization Cross Section For He In The Hyperspherical Coordinate Method, Donald L. Miller, Anthony F. Starace
Anthony F. Starace Publications
The hyperspherical coordinate method developed by Macek, Fano, Lin, and Klar to describe two-electron correlations is used for the first time to treat an atomic photoionization process. Using adiabatic approximations for both the initial and the final state, the cross section for the process He +γ +He+1s +e– is calculated and is found to lie 1% higher than the revised experimental data of Samson at threshold, 4% lower at 1 Ryd above threshold, and 12% lower at 1.9 Ryd above threshold.
Heavy Ion Beam Model For Radiobiology, Rose Ann Roth, Robert Katz
Heavy Ion Beam Model For Radiobiology, Rose Ann Roth, Robert Katz
Robert Katz Publications
An ad hoc model of energetic heavy ion beams, including secondary and tertiary particles, has been constructed for predicting radiobiological experiments. While the beam model is relatively primitive, it yields depth-dose and depth-radiobiological calculations in good agreement with experiment upstream of the Bragg peak. Beyond the peak, the model is somewhat coarse grained and seems to underestimate low-LET fragment production. These defects can be repaired at some cost in computer time. Presently a complete set of depth-dose and radiobiological results (RBE, OER, aerobic and hypoxic survival) is obtained in 4–8 min, for a single beam, at a cost of $10. …
Theoretical Potential Curves For Excited States Of Arh And The Rate Of Collisional Quenching Of Metastable Ar By H, R.L. Vance, Gordon A. Gallup
Theoretical Potential Curves For Excited States Of Arh And The Rate Of Collisional Quenching Of Metastable Ar By H, R.L. Vance, Gordon A. Gallup
Gordon Gallup Publications
Energy curves for the ground state and the first seven excited states of ArH have been calculated using the multiconfiguration valence bond (MCVB) method. Important features of the excited curves include two distinct avoided crossings between the lowest Ar*H and the highest ArH* potential energy curves. Using these curves we have made a theoretical analysis of quenching of metastable Ar by collision with H at room temperature. Application of the Massey criterion indicates that the separation of the potential curves in the region of the crossing and the acceleration produced by the fall of the reactant channel potential curve from …
Effect Of Hydrostatic Pressure On The Incommensurate Phase Of K2Seo4, W. Press, C. F. Majkrzak, J. D. Axe, John R. Hardy, N. E. Massa, F. G. Ullman
Effect Of Hydrostatic Pressure On The Incommensurate Phase Of K2Seo4, W. Press, C. F. Majkrzak, J. D. Axe, John R. Hardy, N. E. Massa, F. G. Ullman
John R. Hardy Papers
A neutron scattering study of the effect of hydrostatic pressure on the incommensurate phase transformation in K2SeO4 was performed in order to obtain information concerning the nature of the competing forces that give rise to a structural instability at a general wave vector. It was found that an increase in pressure lowers the transition temperature (dTi/dPi = - 6.5 K/kbar) and results in a smaller value of the initial incommensurate wave vector. The pressure dependence of the incommensurate to ferroelectric phase transition was also investigated (dTc/dPc = …
Addendum To "Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6s Electron In Cesium", Keh-Ning Huang, Anthony F. Starace
Addendum To "Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6s Electron In Cesium", Keh-Ning Huang, Anthony F. Starace
Anthony F. Starace Publications
A previous calculation of the cesium 6s→εp photoionization cross section is extended to include interchannel coupling to the 5p→εd photoionization channels. For photon energies in the range 0.35 a.u.≲ℏω≲1.12 a.u., i.e., just above the near-threshold cross-section minimum, the 6s photoionization cross section is found to be dominated by 5p→5d resonance transitions. No experimental data exist for this energy region.
Supralinearity Of Peak 5 And Peak 6 In Tld-700, Michael P. R. Waligórski, Robert Katz
Supralinearity Of Peak 5 And Peak 6 In Tld-700, Michael P. R. Waligórski, Robert Katz
Robert Katz Publications
Track theory has been applied to an earlier suggestion, that the supralinearity of TLDs at high gamma-ray doses is due to pre-existing 1-hit and 2-hit trap structures, to calculate high-LET response. Measured 60Co dose responses for peaks 5 and 6 in LiF (TLD- 700) were decomposed to yield parameters characterizing each peak as a two-component c-hit mixture. One value of “trap radius” was assigned to each two-component representation, different for peak 5 and for peak 6, to calculate their responses for H, He, C, O, and Ne bombardments. Calculations reproduce experimental features of the heavy ion response of TLD-700, and …
Very-Long-Lived Metastable Vibrational States Of Ba2++ , Stanley J. Sramek, J.A. Macek, Gordon A. Gallup
Very-Long-Lived Metastable Vibrational States Of Ba2++ , Stanley J. Sramek, J.A. Macek, Gordon A. Gallup
Gordon Gallup Publications
Potential-energy curves for the 1 Σg+ states of Ba2++ are exhibited. The ground-state curve shows a local minimum lying 0.0562 a.u. above the energy at infinite separation, and a local maximum lying at 0.0618. These features form a potential well in which metastable vibrational states can exist. The lifetimes are estimated as high as 10197 sec, using the WKB method. Considerations regarding experimental formation and detection of bound Ba2++ are discussed.
Photoionization Of The 5S Subshell Of Xenon: A Multichannel K-Matrix Calculation Including Spin-Orbit Interactions, Keh-Ning Huang, Anthony F. Starace
Photoionization Of The 5S Subshell Of Xenon: A Multichannel K-Matrix Calculation Including Spin-Orbit Interactions, Keh-Ning Huang, Anthony F. Starace
Anthony F. Starace Publications
Ab initio theoretical calculations are presented for the cross section, angular distribution, and spin polarization of photoelectrons for the 5s subshell of xenon. Starting from an initial basis of nonrelativistic Hartree-Fock wave functions, the authors treat the effect of final-state spin-orbit interaction in the Breit-Pauli approximation exactly. Electrostatic correlations between the 5s and 5p subshells are also included. Good agreement is obtained with experiment in the case of the photoionization cross section, but only qualitative agreement with experiment and with other theoretical calculations is obtained in the case of the photoelectron angular distribution due to the difficulty …
Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 6087, Edward G. Schmidt
Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 6087, Edward G. Schmidt
Edward Schmidt Publications
Four-color and Hβ photometry has been obtained for 16 stars in the open cluster NGC 6087. Based on this photometry the membership of these stars in the cluster is discussed. Using stars which appear to be members a color excess of E(b – y) = 0m.23 and a distance modulus of (V0 – Mv) = 9m.60 are derived. This distance modulus is about 0m.4 less than previous values and indicates a lower luminosity for the Cepheid member, S Nor, than is currently accepted.
Theoretical Lattice-Dynamical Studies Of The Incommensurate Phase Transformation In K2Seo4, M. S. Haque, John R. Hardy
Theoretical Lattice-Dynamical Studies Of The Incommensurate Phase Transformation In K2Seo4, M. S. Haque, John R. Hardy
John R. Hardy Papers
We have made detailed lattice-dynamical studies of the origin of the incommensurate phase transition in potassium selenate. These were based on a rigid-ion model with Coulomb interactions, and also short-range interactions between restricted numbers of close neighbors. The associated short-range force constants were determined using the static equilibrium conditions for the crystal and the observed Raman frequencies. The calculations were made for the room temperature structure using the quasiharmonic approximation in which the effects of varying temperature were simulated by varying the short-range force constants. In this way we were able to show that the crystal has a low-frequency optic …
Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 129, Edward G. Schmidt
Four-Color And Hβ Photometry Of Stars In The Galactic Cluster Ngc 129, Edward G. Schmidt
Edward Schmidt Publications
Four-color and photometry has been obtained for 22 stars in the field of the open cluster NGC 129. Based on this photometry, the membership of these stars in the cluster is discussed and it is found that many are field stars. The color excesses for cluster members obtained here range from E(b – y) = 0.207 to 0.513 and are larger than those found from previous UBV photometry. It has been suggested that this cluster contains a nonvariable Cepheid strip star. However, the present reddening places this star at the edge of the instability strip. A true …
Angular And Energy Distribution Of Electrons From 15- To 150-Kev H0+He Collisions, M. Eugene Rudd, J. S. Risley, J. Fryar, R. G. Rolfes
Angular And Energy Distribution Of Electrons From 15- To 150-Kev H0+He Collisions, M. Eugene Rudd, J. S. Risley, J. Fryar, R. G. Rolfes
M. Eugene Rudd Publications
An electrostatic analyzer positioned at various angles has been used to measure absolute values of cross sections for electron production in collisions of neutral hydrogen atoms with helium as a function of the angle and energy of the ejected electrons. These cross sections are compared with corresponding ones for proton and electron impact to infer the mechanisms of electron production. A prominent peak in the energy distribution due to electron loss from the projectile occurs at an electron velocity equal to that of the projectile. At very low electron energies the similarity of the energy distribution to that due to …
The Cepheid Luminosity Scale, Edward G. Schmidt
The Cepheid Luminosity Scale, Edward G. Schmidt
Edward Schmidt Publications
The distance moduli of galactic clusters containing classical Cepheids are being redetermined using the four-color and Hβ photometric system. The results for four clusters are presented here and it is found that the distance moduli are smaller than previous values. Possible reasons for this discrepancy are discussed.
A Graphical Method For Calculating First Order Transition Matrices For Open-Shell Atoms In The Random Phase Approximation, Anthony F. Starace, Siamak Shahabi
A Graphical Method For Calculating First Order Transition Matrices For Open-Shell Atoms In The Random Phase Approximation, Anthony F. Starace, Siamak Shahabi
Anthony F. Starace Publications
A graphical procedure is presented for calculating first order transition matrices for a general (open-shell) atom. The first order transition matrix may be used to calculate matrix elements of a general one-body operator of rank λ in orbital space and σ in spin space. In the random phase approximation we obtain a set of N + N′ coupled differential equations for N final state radial functions and N′ initial state radial functions which completely determine the first order transition matrix for an atomic system having N final state channels. (The relation of N′ to N is dependent on the atomic …