We present conclusive evidence that the passage of fast ${\mathrm{Ne}}^{+}$ ions through a thin foil results in a high degree of alignment of the transmitted excited atoms and ions. We use these observations to measure the mean lives and $g$ values of electronic levels in atoms and ions. Our methods also lend themselves to the measurement of the speeds of fast atoms and ions.

Meeron's recent theorem excludes phase transitions in the density interval $0<~\frac{\rho }{{\rho }_0}<0.147\mathrm{}$ for hard disks and $0<~\frac{\rho }{{\rho }_0}<0.091\mathrm{}$ for hard spheres (${\rho }_0$=close-packed density). The apparent phase transitions indicated by machine calculations lie at much higher densities.

The shape and amplitude of the electron-plasma wave spectrum resulting from a "gentle bump" on the tail of the electron velocity distribution of a plasma is measured and found to be in good agreement with quasilinear theory.

New theoretical results are presented for the probability of exciting surface oscillations (optical phonons or plasmons) by fast electrons reflected from the surface of a thin crystal film. Both specular and Bragg reflections are considered and the effect of the finite slab thickness is included. The theory explains successfully the energy-loss spectra measured by Powell on metallic surfaces and recent measurements by Ibach on ZnO surfaces.

The long-range order in $\beta$-brass has been determined from x-ray measurements of integrated intensities of superlattice reflections. Analysis of the data includes allowance for the observed appreciable difference between the two Debye-Waller factors. The long-range order parameter is found to be significantly greater than the values from current Ising-model calculations over a wide range of temperatures below the critical region.

A tight-binding calculation of the band structure of magnetite with Verwey ordering alone does not, for any strength of interatomic Coulomb energy, yield insulating behavior; for this, additional orderings in transverse directions are required. Below the Verwey temperature $T_{\mathrm{V}}$, iron $B$-site charge densities are fractional (nonionic), continuous functions of $T$, and the gap is probably indirect with $T$-dependent band extrema ($T\lesssim T_{\mathrm{V}}$). There is semimetallic behavior above $T_{\mathrm{V}}$. Multiple orderings allow a natural description of the extra Mössbauer spectra and neutron- and electron-diffraction patterns recently observed.

The temperature-dependent part of the electrical resistivity of a dilute alloy at low temperatures is generally much larger than that of the pure host metal. A simple calculation based on the relaxation of the usual conservation requirements for electron-phonon scattering in the alloy leads to a formula which contains no free parameters and which agrees well with experiment for a wide variety of alloy systems.

A mechanism is suggested to explain the temperature dependence and magnitude of a contribution to the electrical resistivity observed in a number of alloys.

A band calculation as a function of lattice parameters employing the Lin and Falicov pseudopotential is given which predicts an isostructural electron transition in As of the type described by Lifshitz. Experimental evidence that such a transition occurs in As at a pressure of about 1.8 kbar is reported.

We have observed magnetic-field—induced resonance in Raman-scattering cross sections. The resonance enhancement for 1LO scattering from CdS, obtained with 4765 Å, is a factor of ∼30 at 90 kG. The results are interpreted in terms of resonance of the incident photon with the Landau levels of the ${\Gamma }_7$ conduction and valence bands. With a 4579-Å laser, we see a resonance of the Stokes 3LO process. We explain this as the resonance of the scattered photon.

It is shown that the coherent-potential approximation is capable of explaining the densities of states of Cu-rich Ni-Cu alloys as obtained from recent photoemission experiments. The coherent-potential approximation predicts the formation of a separate Ni $d$ band for these alloys, this being consistent with the qualitative picture of Friedel-Anderson virtual bound states. This picture cannot be obtained from either the rigid-band model or the virtual-crystal approximation.

Neutron-scattering measurements of the spectral density ${\chi }_T\left(\overrightarrow{\mathrm{q}}\right)F(\overrightarrow{\mathrm{q}},\omega )$ of the spin-relaxation function in the Heisenberg paramagnet RbMn${\mathrm{F}}_3$ are presented for the temperature range $T_{\mathrm{N}} \mathrm{to} 3.55T_{\mathrm{N}}$. Spectral densities, utilizing shape functions $F(\overrightarrow{\mathrm{q}},\omega )$ determined by Reiter, are compared directly with experiment on an absolute basis. Some interesting properties of ${\chi }_T\left(\overrightarrow{\mathrm{q}}\right)$ are reported and comparison of measured values is made with recent calculations by Collins.

A vector-polarized deuteron beam of energy 12.3 MeV has been used to measure differential cross sections and vector analyzing powers for the reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}\mathrm{}(d,t)\mathrm{}$, leading to the $p_{\frac{1}{2}}$ ground state, $f_{\frac{5}{2}}$ first excited state, and $p_{\frac{3}{2}}$ second excited state of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$. The vector analyzing powers for the two $l=1\mathrm{}$ transitions differ strikingly. This $j$ dependence is well reproduced by distorted-wave Born-approximation calculations.

Several (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $d$) and ($d,n$) transitions on Zr and Mo targets leading to unbound isobaric analog states, which had previously been reported anomalous in comparison with distorted-wave Born-approximation predictions, have been recalculated using a different form-factor prescription. Broad overall agreement with experiment is obtained, indicating that both the nuclear structure and the reaction mechanism are normal.

The cascade $\gamma$-ray decay of states at 19.9 and 20.4 MeV in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ has been observed using the reaction ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(p,{\gamma }_2\gamma ){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. These states appear to have the properties expected of giant dipole states based on the $J^{\pi }=3^{-}$ state at 6.13 MeV. Together with earlier work, the result implies that giant dipole states based on the $J^{\pi }=0^{+}$ state at 6.05 MeV are displaced significantly from the energies expected from a simple weak-coupling model.

The pairing-plus-quadrupole model is improved and extended to $I=6\mathrm{}$ states. This microscopic theory gives the parameters of the first-order band-mixing theory of Bohr and Mottelson, as well as most of the higher order corrections revealed by the recent measurements of $E2\mathrm{}$ matrix elements. The increase in the intra-ground-band transitions as well as the depression of the ground-band levels compared with their rotational-model values are reproduced.

We have measured the yield of ${\pi }^{+}{\pi }^{-}$ pairs from the reaction $\gamma +\mathrm{C}\to \mathrm{C}+{\pi }^{+}+{\pi }^{-}$ in the invariant-mass region $0.6<m<\mathrm{}1.8\mathrm{} \frac{\mathrm{GeV}}{c^2}$. The result, based on ${10}^5$ events, shows that the data, at high energy and very small momentum transfer, exhibit an enhancement in the region $1.3<m<\mathrm{}1.8\mathrm{} \frac{\mathrm{GeV}}{c^2}$.

We report the results of a proton-proton bremsstrahlung experiment. The cross sections were measured over wide angular ranges using a wire-chamber spectrometer. Where possible, comparisons are made with the theoretical predictions of the Hamada-Johnston potential.

The experimental data for the single-pion distribution in the reaction ${\pi }^{-}+p\to {\pi }^{\pm }$ + anything at incident energies between 2.5 and 6 GeV and at 25 GeV show evidence for a limiting distribution and scaling behavior. The slopes of the logarithmic increase of the average ${\pi }^{\pm }$ multiplicities calculated from the 25-GeV data are found to be comparable with those obtained from accelerator $\mathrm{pp}$ reactions and cosmic-ray experiments. We make some comments on possible future experiments and on an apparent discrepancy between experiments at 10, 20, and 30 GeV and a limiting distribution.

The scattering theory of laser atoms developed by Berman and Lamb is found to have implications for the collision theory of a high-intensity laser. Assuming scattering in the lower laser state ($2p_4$) to dominate, one can fit the experiments on a 0.63-μm He-Ne laser by Cordover and Bonczyk.