It has been conjectured, on the basis of the Atkinson-Cabrera solution for the steady motion of a dislocation in a modified Frenkel-Kontorova model, that dislocations can be accelerated from subsonic to supersonic velocities. Computer-simulation results are presented to show that the regular dislocation motion assumed in the Atkinson-Cabrera solution breaks down, and the solution ceases to be valid before the sound velocity is reached.

By measuring the energy spectra of backscattered 1-MeV ${\mathrm{He}}^{+}$ ions from Al-0.09 at.% Mn crystals, it was found that Mn atoms were displaced from lattice sites by irradiation with 0.3-1.0-MeV ${\mathrm{He}}^{+}$ ions at 35°K. Annealing results and an analysis of $〈110〉$ and $〈111〉$ axial channeling and {100} planar channeling indicated that the Mn atoms were displaced by trapping irradiation-induced interstitial Al atoms, forming Al-Mn atom pairs in the $〈100〉$ dumbbell configuration.

The critical magnetic field producing spin flop in many antiferromagnets is too small to soften a three-dimensional magnon, i.e., to remove the energy barrier between the equal-energy phases. The barrier can be bypassed, however, via the softening of surface magnons in a smaller field, forming two-dimensional surface-spin-flop states, which broaden with increasing field and which catastrophically spread inward across the three-dimensional material as the critical field is approached.

The contribution of $n$-body forces to nuclear matter energy is summed in closed form as a function of the nuclear density. It is seen that they provide an increasing amount of binding as the density increases beyond ordinary nuclear density. The presence of correlations suppresses this effect, but does not destroy it fully. The physics behind these phenomena is discussed.

Compound-nuclear reactions induced by bombardment of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ targets with 20-60-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ beams have been used to study $\gamma$ transitions between high-spin states in nuclei in the mass region $32<~A<~44$. Results for ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ are presented to exemplify the method and results. The $\gamma$-ray decay of states with probable spins up to $\frac{19}{2}$ are observed in both nuclei.

Measurements of the analyzing power and the differential cross section in the nuclear continuum for the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(p, p^{\prime })$ initiated by 60-MeV polarized protons provide strong evidence for a quadrupole ($E2\mathrm{}$) interpretation for the giant resonance at $E_x\approx \frac{63}{A^{\frac{1}{3}}}$ MeV. A resonance approximately 3 MeV lower in excitation energy has also been observed.

We describe a detailed and successful experimental search for fine angular oscillations in the reaction ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ at a laboratory energy of 50 MeV. Also presented is a qualitative, analytic description of the reaction extracted from the distorted-wave Born-approximation partial-wave analysis in which the universality of the oscillations is clearly indicated.

A pulsed beam of polarized neutrons and a polarized ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ target have been used to determine the spins of 65 resonances below 60 eV. Comparison of these spin assignments with those determined by less direct methods reveals poor agreement in general. Interpretation of recent data on the angular distribution of fission fragments from aligned ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ with the present spin assignments reveals the absence of the $K=0\mathrm{}$ channel and an apparent admixing of transition states.

The inelastic reaction $p+p\to p+X$ is studied at 205 GeV/c. The distribution of the square of the missing mass, $M^2$, shows a large diffractivelike peak at low $M^2$ due to two-, four-, and six-prong events. The slope of the invariant cross section versus $t$ decreases with increasing $M^2$. The energy dependences of the multiplicity moments for the recoiling system $X$ are similar to those for corresponding moments for $p+p\to \left(n \mathrm{charged}\mathrm{particles}\right)$.

We have observed x rays produced in atoms formed by ${\Sigma }^{-}$ hyperons with both lead and uranium nuclei. The fine-structure splitting of the x rays can be used to determine the magnetic moment of the ${\Sigma }^{-}$ particle by a method similar to that used in a recent measurement of the $\overline{p}$ magnetic moment. Although the fine-structure splitting for the ${\Sigma }^{-}$ atom was not distinctly resolved, our measurement can place an upper limit on the fine-structure splitting and hence the magnetic moment. We find that the magnetic moment lies in the range $-1.6<\mu <0.8\mathrm{}$ in nuclear magneton units.

The slope $b\left(s\right)\mathrm{}$ of the forward diffraction peak of $p-p$ elastic scattering has been measured in the momentum-transfer-squared range $0.005\lesssim \mathrm{}\left|t\right|\mathrm{}\lesssim 0.09$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ and at incident proton energies from 8 to 400 GeV. We find that $b\left(s\right)\mathrm{}$ increases with $s$, and in the interval $100\lesssim s\lesssim 750$ ${\mathrm{}\left(\mathrm{GeV}\right)\mathrm{}}^2$ it can be fitted by the form $b\left(s\right)=b_0+2\mathrm{}{\alpha }^{\prime }\ln s$ with $b_0=8.23\mathrm{}\pm 0.27$, ${\alpha }^{\prime }=0.278\mathrm{}\pm 0.024$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$.

The cosmic-ray muon charge ratio has been measured for muon momenta 0.7-4.5 TeV/c. It has also been calculated for a constant primary composition by applying scaling to nuclear-target data. The measurements, together with those at lower energies, are in good agreement with our predictions for primary collision energies up to 40 TeV.

The temperature dependence of electrical conductivity of rf-sputtered amorphous Ge, Si, and Ge-Si films as functions of annealing temperature and time have been investigated for $350\gtrsim T\gtrsim 77$ K. Annealing shifts the hopping region to lower temperatures. We find that reasonable values of Mott's parameters are obtained only for properly annealed specimens in the true hopping-conduction region.

We report for the first time spin-flip scattering from free holes in a semiconductor. We observe heavy holes in $p$-type ZnTe with a $g$ value of $g_{\mathrm{hh}}=2.12\mathrm{}$. Two additional photo-excited features are observed. One with $g=1.74\mathrm{}$ is tentatively assigned as due to light holes; the other has $g=1.07\mathrm{}$ and could be due to conduction electrons or to transitions between light and heavy hole bands. This is the first determination of ZnTe $g$ values.

It is shown that the differential cross section for the reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(p, t)$ leading to the $3^{+}$ (1.34-MeV) state of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ can be understood in terms of a two-step $(p, d)-(d, t)$ mechanism.

The neutron polarization asymmetry in neutron-deuteron scattering has been measured from 44.5° to 160° (c.m.) neutron angle. The results display quantitatively the same structure as proton-deuteron polarization data, but discrepancies appear for angles corresponding to those near the minimum of the differential cross section. In this region the polarization is considerably more negative than in the proton-deuteron case, and both are more negative than current theoretical predictions.

Sum-rule techniques are used to evaluate total $\mu$-capture rates. They turn out to be strongly dependent on the mean nuclear excitation energy, whose behavior along the nuclear table is discussed.

Differential cross sections and analyzing powers for inelastic scattering of 24.5-MeV protons from ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ have been measured, with special attention to the excitation of states which occur in the two-phonon region. The coupled-channel theory is used to interpret the excitation of the two-phonon states. An appreciably better fit to the data for the excitation of the second $2^{+}$ state is obtained if a small admixture of the one-phonon state is assumed. However, a strong component of a $4^{+}$ one-phonon state needs to be admixed to the $4^{+}$ two-phonon state.

Gravitational perturbations in the neighborhood of a point charge can induce electromagnetic radiation even if the symmetry of a configuration indicates that the charge is not moving. Wave equations for the electromagnetic radiation are given in the Newman-Penrose formalism, and the radiation for a simple physical system is calculated and discussed.

The Euclidean-Markov field, extensively used in constructive quantum field theory, is shown to be the same as the lowest energy generalized stochastic process associated with classical field theory through the procedure of Nelson's stochastic mechanics. As a result, the underlying four-dimensional manifold, on which the Markov field is defined, can be considered as the physical space-time.