Drift mobility and conductivity measurements were made between 290 and 85°K on amorphous silicon specimens prepared by glow-discharge decomposition of silane. The results suggest that excess electrons drift in the extended states with a mobility of about 10 ${\mathrm{cm}}^2$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{V}}^{-1\mathrm{}}$. At lower temperatures, phonon-assisted hopping occurs through localized states occupying a range of 0.2 eV below the extended states. Conductivity results also suggest hopping transport near the Fermi energy.

The band-structure-matching formalism has been used to calculate the elastic intensities of (00), (01), (11), and (02) beams for normal incidence on the (001) surface of A1 within an energy range between 0 and 10 Ry. The band structure was calculated using an orthogonalized plane-wave-based pseudopotential which contained no adjustable parameters. Symmetry was used to its fullest extent in expanding the crystal Bloch functions in order to obtain very accurate numerical results. Comparison with experiment shows good agreement with regard to the positions and relative intensities of the peaks.

The band-matching approach has been used to calculate low-energy electron-diffraction intensity curves for the basal cleavage plane of beryllium. An approximation to the exact theory, made possible by the presence of strong inelastic scattering, has enabled these curves to be calculated very rapidly for general angles of incidence and with a detailed, nonlocal potential with no adjustable parameters. There is striking similarity between the calculated intensities and the detailed experimental work of Baker.

A criterion for localization of electron states in disordered materials is presented. Applications to binary alloys, made using the self-energy calculated in the coherent-potential approximation, confirm the Mott-Cohen-Fritzsche-Ovshinsky model in detail. Mobility edges occur inside the band edges. A mobility gap can appear within the band. The band can split into sub-bands, each with mobility edges. Below a critical concentration, an Anderson transition, where the minority sub-band becomes entirely localized, can occur.

The magnetic properties of Pr and Nd single crystals have been studied by neutron-diffraction and susceptibility measurements. In contrast to earlier results on polycrystals, monocrystalline Pr is found not to be magnetically ordered, because of crystal field effects, but a magnetic field induces a large moment. Anisotropic effective exchange results in a large magnetic anisotropy. The complex magnetic structure of Nd is substantially modified by a magnetic field.

The existence of antiferromagnetic order in the monoclinic phase of ${\mathrm{V}}_2$${\mathrm{O}}_3$ has been confirmed by a neutron polarization analysis experiment. Conventional neutron-diffraction experiments on powders and single crystals have been performed to determine the magnetic structure. The observations are in accord with a model in which the V moments are ferromagnetically coupled in monoclinic (010) layers, or hexagonal (110) layers, with a reversal between adjacent layers. The ordered moment is (1.2 ± 0.1)${\mathrm{\mu }}_{\mathrm{B}}$ per V atom.

Precise measurements of the masses of ${}_{}{}^9{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{21}{}_{}{}^{}\mathrm{Mg}$ have been made using a magnetic spectrograph. The results are used to test the isobaric multiplet mass equation.

The mass excess of ${}_{}{}^{13}{}_{}{}^{}\mathrm{O}$ has been determined to be 23.107 ± 0.015 MeV. This yields a value for $d$, the coefficient of ${T_Z}^3$ in the isobaric multiplet mass equation, of -0.8 ± 3.4 keV for the $A=13\mathrm{}$ quartet. Additional values for $d$, obtained from new measurements of the masses of ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{21}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{25}{}_{}{}^{}\mathrm{Si}$, are also consistent with zero.

Close similarities are found in the gross structures of the excitation functions from the elastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ from ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$. The picture emerging from the optical-model analysis of these data is that of an interaction potential which is totally absorbing for the low-$l$ partial waves and which is very transparent for the surface partial waves.

Charge and magnetic form factors are calculated using solutions of the three-nucleon Faddeev equations with the local two-nucleon potentials of Reid and of Malfliet and Tjon. The results give reasonable agreement with the data up to 9-${\mathrm{fm}}^{-2\mathrm{}}$ transfer, but do not reproduce the minimum at 11.8 ${\mathrm{fm}}^{-2\mathrm{}}$ in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ charge form factor.

A new technique for the study of the beta rays emitted by polarized nuclei is presented. This technique uses two silicon detectors arranged in coincidence so as to discriminate against gamma rays and back scattering from the detectors. This technique has been used to study the asymmetry of the beta rays in the decay of ${}_{}{}^{110m}{}_{}{}^{}\mathrm{Ag}$.

The $g$ factor of the 24-nsec ($h_{\frac{9}{2}}{i}_{\frac{13}{2}}$) ${11}^{-}$ state of ${}_{}{}^{210}{}_{}{}^{}\mathrm{Po}$ has been determined to be 1.090±0.016 by the spin-rotation method in the reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(\alpha ,2n)$. The anomalous ${g_l}^{\mathrm{e}\mathrm{f}\mathrm{f}}$ factor of 1.09±0.02 has been deduced from this value and the known $g$ factor of $h_{\frac{9}{2}}$ under the assumption of the renormalized single particle operator $\overrightarrow{\mu }={g_l}^{\mathrm{e}\mathrm{f}\mathrm{f}}\overrightarrow{\mathrm{l}}+{g_s}^{\mathrm{e}\mathrm{f}\mathrm{f}}\overrightarrow{\mathrm{s}}$.

We find that the "quark" track recently reported by Chu et al. can be simply explained in terms of a normally charged cosmic ray entering the bubble chamber at an early time.

Differential cross-section measurements for ${\pi }^{+}p$ and ${\pi }^{-}p$ elastic scattering at 3.0, 3.5, 4.0, and $5.0 \frac{\mathrm{GeV}}{c}$ are presented for center-of-mass scattering angles between 55° and 130°. A shoulder near $t=-0.9\mathrm{}$ and a dip near $t=-3.0\mathrm{} {\left(\frac{\mathrm{GeV}}{c}\right)}^2$ are seen in the data throughout this momentum range.

We present evidence that the inclusive reaction $p+p\to \pi$ + anything approaches a scaling limit at accelerator energies.

A new technique of observing the Lamb shift which combines beam-foil and radiofrequency spectroscopy techniques is described. Measurements are made at zero magnetic field by sweeping the radiofrequency field. A radiofrequency hyperfine state selector is used to reduce the effect of overlapping lines.

A tunable dye laser has been used to measure the fine-structure splitting of the ${}_{}{}^2{}_{}{}^{}P$ state of ${\mathrm{S}}^{-}$ in a crossed-beam photodetachment experiment. These measurements verify photodetachment threshold laws and provide the most accurate experimental determination of any electron affinity.

It is found that resistivity causes the self-consistent Tokamak equilibria to be unstable towards rotation about the magnetic axis. The growth rate is $\sim \frac{2{\pi }^2\eta R^2\beta }{{\iota }^2{a}^4}$, with $\eta$ the resistivity, $R\left(a\right)\mathrm{}$ the major (minor) radius, and $\iota$ the rotational transform. This is comparable with the skin penetration rate $\sim \frac{\eta }{a^2}$ of the poloidal field. We employ simple magnetohydrodynamic theory with resistivity, without considering possible stabilization by other dissipative effects. The quantities $\eta$, $\beta$, and $\frac{a}{R}$ are regarded as small. Our result agrees with one obtained previously in the case of an externally fixed field.

In this Letter we propose an interpretation of a recent experiment on the anomalous absorption of a powerful electromagnetic wave in a collisionless plasma. The electromagnetic wave excites an instability, driving up the ion-density fluctuations. The ion waves scatter energy efficiently from the electromagnetic wave into longitudinal plasma modes which are then absorbed in the plasma.

We show how the Zeeman pattern of the "satellites" of spectral lines produced by the high-frequency Stark effect can be used to determine the direction of an oscillating electric field relative to the magnetic field. We illustrate the use of this effect as a diagnostic technique in plasma physics by observations of the Zeeman pattern of the "plasma satellites" of the 4922-Å He-I line produced by high-frequency electric fields in a beam-plasma interaction.