Physics Commons^™

Dissociative Attachment From The O2 (A1 Δ G) State, P.D. Burrow

Paul Burrow Publications

The dissociative attachment cross section for production of O^- by electron impact on the metastable O₂ (a¹ Δ _g) state is studied. The cross section is found to be 4.6 ± 1.3 × 10^-18 cm² at its maximum. From the measured energy dependence, we infer that the dissociative attachment process takes place through the O^2̅ (² П_u) state as in the case of O^- production from the O₂ ground state. The information thus obtained is used to estimate the portion of the cross section for excitation of the …

Raman Spectrum Of Gadolinium Molybdate Above And Below The Ferroelectric Transition, Frank Ullman, B. J. Holden, B. N. Ganguly, John R. Hardy

John R. Hardy Papers

90 °-scattered Raman spectra of single-domain gadolinium molybdate have been obtained at room temperature and above the 159 °C ferroelectric transition on several crystal orientations. Lines in the 0-200-cm^-1 range can all be associated with Raman-active phonons and are identified by symmetry considerations, scattering-efficiency calculations, and comparison of spectra for different crystal orientations. Lines in the 200-1000-cm^-1 range can be identified with coupled vibrations of tetrahedral molybdate ions. Spectra for frequencies above 1000 cm^-1 originate from impurity flourescence. The effect of the presence of multiple domains on the spectra was determined; the observed differences between single-domain and …

Lattice Dynamics Of A Rigid-Ion Model For Gadolinium Molybdate, L. L. Boyer, John R. Hardy

John R. Hardy Papers

Results of lattice-dynamical calculations are presented which support the view that the ferroelectric phase transition in gadolinium molybdate (GMO) arises from the softening and ultimate instability of a doubly degenerate zone-edge mode of the high-temperature paraelectric phase. We have used a rigid-ion model in which the short-range force constants are obtained from a detailed knowledge of the crystal structure together with the conditions imposed by the requirement that the crystal must be in static equilibrium under the combined influence of both Coulomb and short-range forces. Our results show that this type of approach is very useful when one is dealing …

Magnetic Interactions And High-Field Magnetization In Dilute Magnetic Alloys , J.M. Franz, David J. Sellmyer

David Sellmyer Publications

Magnetic interactions have been investigated in Cu(Mn) and Cu(Fe) alloys with concentrations ranging from several hundred to several thousand ppm. In each system two sets of alloys were prepared in different ways to test for sensitivity to structrual modifications. In the Cu(Mn) alloys there was very little difference in magnetic properties of the two sets of alloys which is consistent with the expectation that the Cu(Mn) alloys form good random solid solutions. The magnetic properties were compared with the recent mean-random-field theory of Klein in the low-temperature limit. It was found that the theory is able to explain the concentration …

Comment On "Length And Velocity Formulas In Approximate Oscillator-Strength Calculations", Anthony F. Starace

Anthony F. Starace Publications

A previous paper by Starace showed that the length formula for the electric-dipole matrix element is the only consistent one for calculations that solve for the exact eigenfunctions of an approximate Hamiltonian containing a nonlocal potential. It is emphasized here that disagreement between such a length-formula calculation and experiment indicates inadequacy of the approximate Hamiltonian and not that the velocity formula may be preferable.

Magnetoresistance In Iron And Cobalt To 150 Koe , R.V. Coleman, R.C. Morris, David J. Sellmyer

David Sellmyer Publications

Magnetoresistance anisotropy and field dependence have been studied in single crystals of iron and cobalt in fields up to 150 kOe in the temperature range 1-4.2 K. The crystals of iron and cobalt had residual resistance ratios up to ∼4600 and ∼400, respectively. The relation Δρ/ρ₀=aBⁿ has been studied for both metals and in the case of iron the exponent n approaches values in the range 1.8-1.9 for fields up to 90 kOe and then decreases to the range 1.3-1.5 at 150 kOe. This decrease in the exponent has been observed for all field and current …

Quasi-Landau Spectrum Of A Hydrogen Like Atom In A High Magnetic Field, Anthony F. Starace

Anthony F. Starace Publications

A two dimensional semiclassical approximation is used to examine the σ polarization spectrum of a hydrogen like atom in a strong magnetic field. Resonances above the zero field ionization limit are found and their energy separations are computed over the region from the ionization limit to 40 ħω_c above, where ω_c is the cyclotron frequency, for magnetic fields of 10, 17, 25, 32, 40 and 47 kG. At the ionization limit the separation between resonances is found to be 1.500 ħω_c, independent of magnetic field strength, which is in agreement with a separation of 1.5 ħω …

Evaluation Of An Experiment In Computer -Assisted Tutoring, Stephen L. Cunningham, Robert Fuller

Robert G. Fuller Publications

It was made apparent from the presentations at the Conference of Computers in Undergraduate Science Education that very few Computer-Assisted Instructional (CAI) programs in physics attempt to evaluate the performance of computer- tutored students in comparison with a control group. In this note, we discuss an experiment in which 23 beginning physics students out of a class of 64 were given a computer-administered tutoring test in place of the regular review recitation session prior to an hour exam on relativity. The performance of the computer-tutored group on the exam was compared to the performance of the rest of the class.

Static Equilibrium Conditions For A Rigid-Ion Crystal, L. L. Boyer, John R. Hardy

John R. Hardy Papers

The equilibrium requirements for a static ionic crystal impose a number of constraints on the short-range forces which become increasingly more important when one is dealing with complex structures. These constraints are presented and discussed for a general rigid-ion lattice, and a specific discussion is presented for the wurtzite structure.

Projected Hartree Product Wavefunctions. Vi. Natural Orbital Ci Expansions In Nonsinglet Cases, R.D. Koller, Gordon A. Gallup

Gordon Gallup Publications

The NSO's and NO's have been determined for some wavefunctions for Li, Be¹⁺, B²⁺, C^{3+ 2}S, and Be ³S wavefunctions containing radial correlation. It is shown how the NO's may be utilized to form rapidly converging CI expansions in general. The role of the NSO's in this problem is discussed. ©1973 The American Institute of Physics

Determination Of The Origin Of The 10.6-Pm Absorption In C02 Laser Window Materials, John R. Hardy, B. S. Agrawal

John R. Hardy Papers

Theoretical studies are presented which show that it should be possible to determine whether the absorption at 10.6 pm in alkali halides is due to impurities or whether it is intrinsic. These studies show that the temperature dependence of the measured absorption should be very different for intrinsic multiphonon absorption as compared with defect-activated absorption.

Absolute Line Strengths By Analysis Of Lu-Fano Plots With Application To Excited State Transitions In Neon, Anthony F. Starace

Anthony F. Starace Publications

Using energy eigenfunctions obtained by semi-empirical analysis of the Lu-Fano plot of energy level positions and employing the Coulomb approximation of Bates and Damgaard, we calculate absolute line strengths for transitions between the neon two-channel Rydberg series 2p⁵(²P_3/2,1/2)ns J = 1 and 2p⁵ (²P_3/2,1/2)n′ p J = 0 for n, n' = 3,4. Each Rydberg series is analyzed separately to obtain a set of five parameters which completely define the energy eigenfunctions for all values of n and n'. Interactions between the ns J = 1 …

Projected Hartree Product Wavefunctions. Viii. Relationship Of Dods And Scf Orbitals For Be, Gordon A. Gallup

Gordon Gallup Publications

Projected Hartree product wavefunctions. VIII. Relationship of DODS and SCF orbitals for Be

Production And Decay Of Double L Vacancies In Argon And Phosphorus, M. Eugene Rudd, B. Fastrup, P. Dahl, F. D. Schowengerdt

M. Eugene Rudd Publications

Measurements have been made at two laboratories which indicate that the structure reported at 450-550eV in the electron spectrum from Ar⁺-Ar collisions by Ogurtsov, Flaks, and Avakyan is spurious. It is argued that the double L vacancies which they invoke to explain the structure are more likely to decay by the two-step Auger process L ²→LM²→M⁴ than by the one-step process L²→M³ suggested by these authors. Evidence supporting this is found in our electron spectra from P⁺-Ar collisions, where it is known from energy-loss and charge-state measurements that double …

Autoionization Of He And Autodetachment Of He- Following Bombardment By H+, H2+, He+, And He Atoms, F. D. Schowengerdt, S. R. Smart, M. Eugene Rudd

M. Eugene Rudd Publications

Presented here are experimental results of a study of the systematics of electron emission from discrete states of He and He- as produced by H⁺, H₂⁺, He⁺, and He impacts. The results were obtained by energy analysis of the electrons emitted at angles of 10° to 160°. Projectile energies ranged from 20 to 150 keV. Differential and integrated cross sections are presented for emission of electrons from the 2s² (¹S), 2s2p(³P), the sum of the 2p² (¹D) and 2s2p(¹P) autoionizing levels of He, …

Appendix A: The Use Of The Personalized System Of Instruction (Psi)

Calculus-Based General Physics

STUDY MODULES FOR THE USE OF THESE CBP MODULES

Recommended

1. What is the Philosophy of PSI?

2. How Do I Manage This System?

3. The Care and Feeding of Student Tutors

Optional

4. How to Plan the Content of a Keller Plan Course

5. How to Design a Study Module

6. How to Write Learning Objectives