The absorption and reflection spectra of several amorphous and crystalline III-V semiconductors have been measured in the region from 10 to 30 eV where transitions from the outermost $d$ levels of the cation cores occur. The use of the continuous spectrum of synchrotron radiation of DESY enabled us to resolve considerable structure in the crystalline samples. This structure can be interpreted as due to structure in the density of conduction states and to the spin-orbit splitting of the core level.

The purpose of this Letter is to report the discovery of a polymorphic transformation in Yb and to provide a brief discussion of its significance in relation to recent high-pressure studies. The transformation, $\beta \left(\mathrm{fcc}\right)\leftrightarrow \alpha \mathrm{}\left(\mathrm{hcp}\right)\mathrm{}$, is martensitic, the $\alpha$ phase being the stable form at 1 atm below ∼270°K. The slope of the $\frac{\alpha }{\beta }$ equilibrium boundary, ${\left(\frac{d{T}_{\alpha ,\beta }}{\mathrm{dP}}\right)}_{{270}^{\circ },1\mathrm{} \mathrm{atm}}$, is (-23±8)°K/kbar.

We have observed microwave (3 and 9 GHz) emission from round loop samples of $n$-type InSb at 77°K subjected to dc magnetic and induced 20-MHz electric fields. A theoretical model, which identifies the emission as shot noise produced in localized regions of high electric field where the ionization by electrons is enhanced by the transverse magnetic field, is shown to fit the experimental data.

Magnetic properties are calculated for a spin one-half Heisenberg ferromagnet in which the exchange interactions deviate randomly in strength from the mean interaction. Disorder produces a low-energy peak and a high-energy tail in the density of spin-wave states for a simple-cubic geometry. The ferromagnetic Curie temperature is shown to decrease linearly with disorder; the temperature-dependent magnetization is not otherwise markedly altered.

A new strong-coupling diagrammatic perturbation treatment of the Anderson Hamiltonian confirms in finite order Kondo divergencies for the partition function, associated with an effective $s-d$ coupling $J$ as predicted by the Schrieffer-Wolff transformation. This holds true also for the symmetric case. By summing the diagrams with two conduction-electron intermediate states in the limit $U\to \infty$, a Kondo temperature with $J$ near diverging is obtained.

The reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},t){}_{}{}^{49}{}_{}{}^{}\mathrm{Mn}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Cr}$ have been observed with ground-state cross sections of the order of 1 μb/sr. The results for ${}_{}{}^{49}{}_{}{}^{}\mathrm{Mn}$ are consistent with its predicted mass excess of -37.72 ± 0.08 MeV.

The two-center shell model has been generalized to the shape of two overlapping spheroids with equal mass. In this model shell corrections have been calculated and the potential energy surface of two heavy nuclei has been investigated. The influence of fragment shells in the model gives rise to structure in this surface which supports assumptions of earlier models for the scission point.

The (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$), reaction cross sections on ${}_{}{}^{90,92,94}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{92,94,96,98}{}_{}{}^{}\mathrm{Mo}$ targets have been measured to unbound isobaric analog states. All expected transitions are observed except those to $3s_{\frac{1}{2}}$ analog states which are inhibited. Distorted-wave Born approximation calculations do not explain the anomaly. Other possible explanations are suggested.

The ($\gamma ,np$) reaction is discussed as a probable channel for observation of the $T=T_0+1\mathrm{}$ component of the giant dipole resonance, and experimental evidence is presented in support of this conjecture in the case of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$.

The spectrum of high-energy gamma rays following the capture of negative pions in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ was measured with high resolution. The observed structure in the giant resonance region is the first direct experimental proof of the influence of collective excitations in radiative pion capture. This supports recent theories concerning the analogy between this process and muon capture.

Solid-state convective motions in the molecular-hydrogen mantle of Jupiter are evaluated and the resulting heat flux through the solid (and liquid) layers compared with observations.

Cross sections for $\gamma p\to {\pi }^{-}{\Delta }^{++}$, $\gamma n\to {\pi }^{-}{\Delta }^{+}$, $\gamma p\to {\pi }^{+}{\Delta }^0$, and $\gamma n\to {\pi }^{+}{\Delta }^{-}$ have been measured at 16 GeV for momentum transfers $-t<~2$ Ge${\mathrm{V}}^2$. The charge-symmetric cross sections differ by typically a factor of 2, indicating interference between isoscalar and isovector photon amplitudes. The ratio of ${\pi }^{+}{\Delta }^0$ and ${\pi }^{+}{\Delta }^{-}$ cross sections is not consistent with pure isospin $I=1\mathrm{}$ exchange in the $t$ channel, appreciable $I=2\mathrm{}$ exchange being required. A factor-of-5 discrepancy is found for a vector-dominance plus line-reversal prediction.

We have measured $\frac{d\sigma }{\mathrm{dt}}$ for five $N^{*}$ reactions in the process ${\pi }^{-}+p\to n^{-}+N^{*}$ at incident momenta of 8 and 16 $\frac{\mathrm{GeV}}{c}$ in the range of $\mathrm{}\left|t\right|<1.5\mathrm{} {\left(\frac{\mathrm{GeV}}{c}\right)}^2$. $N^{*}$ bumps are observed at masses of 1.24, 1.41, 1.52, 1.69, and 2.19 GeV. Considerable structure is apparent in the $\frac{d\sigma }{\mathrm{dt}}$ distributions including leveling off for $\mathrm{}\left|t\right|<0.15\mathrm{}$ and dips at larger $t$ in both the $N^{*}\mathrm{}\left(1.24\right)\mathrm{}$ and $N^{*}\mathrm{}\left(1.52\right)\mathrm{}$ reactions. The logarithmic slopes for the four higher mass $N^{*}$'s are identical to those seen in the corresponding reaction in $\mathrm{pp}$ scattering and the cross sections exhibit a similar elasticlike behavior with incident energy.

We report the first theoretical predictions, beyond the simple two- and three-electron systems studied to date, of the positions and widths of autoionizing states involving excited configurations of atomic systems. We have carried out multiconfiguration close-coupling calculations of the ${}_{}{}^2{}_{}{}^{}S_{}^e{}_{}{}^{}$, ${}_{}{}^4{}_{}{}^{}S_{}^0{}_{}{}^{}$, and ${}_{}{}^4{}_{}{}^{}P_{}^e{}_{}{}^{}$ autoionizing states in atomic nitrogen, and found substantial agreement with photoabsorption measurements of a new Rydberg series in the ${}_{}{}^4{}_{}{}^{}P_{}^e{}_{}{}^{}$ state. It should be possible to confirm our predictions of series, such as in the ${}_{}{}^2{}_{}{}^{}S_{}^e{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}S_{}^0{}_{}{}^{}$ states, in ion-bombardment experiments.

Preliminary investigations of another approach to the injection phase of "Astron"-like devices are reported. A relativistic electron annular beam was passed through a cusped magnetic field with 25% efficiency and produced a rotating electron cloud. Gyrating electron behavior was examined in three magnetic field configurations by diamagnetic loops and x-ray detectors. Reduction of magnetic field intensity ranged from 15 to 32%, and confinement times of 0.4 to 3.0 μsec were obtained, depending upon the field configurations.

Ultrasonic measurements (2 to 6 MHz) on a room-temperature nematic liquid crystal have shown the attenuation to vary strongly with the angle $\theta$ between the sound-wave propagation direction and the direction of an aligning magnetic field. The velocity change is quite small, amounting to some 0.1% between the $\theta ={90}^{\circ }$ and the $\theta =0^{\circ }$ case. The orientation-dependent attenuation is of the hysteresis type.

The viscous drag of the normal-fluid component on moving superfluid vortex-line cores is shown to have two effects: to push the vortex lines toward the film surface and to enhance the film-creep velocity. A class of experiments in the millidegree temperature range is proposed in order to test for the presence of vorticity in helium film creep.

Shock waves traveling at speeds in excess of ${10}^8$ cm/sec (Mach number ≥ 1000) in deuterium gas at 50 mTorr and room temperature ($n_1=1.3\mathrm{}\times {10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$) have been created in a 3-m-long, electromagnetically driven coaxial shock tube, and neutrons have been observed.

Reflection measurements have been made for the first time on single-domain cholesteric liquid-crystal films. We observed spectral structure and polarization character with obliquely incident light never seen with the previously studied disordered films. We also obtained numerical solutions to Maxwell's equations for obliquely incident light in such materials by a new method. Our reflectivity measurements agree fairly well with computations based on Oseen's spiraling-dielectric-ellipsoid optical model for cholesteric systems.

High-resolution photoemission spectra obtained from ferromagnetic nickel (295°K, $0.47T_C$) and paramagnetic nickel (678°K, $1.07T_C$) give no evidence of a change in the position of the $d$-electron peak near the high-energy cutoff of the photoelectron distribution within the experimental uncertainty of ±0.05 eV. On the other hand, a calculation of the spectra based on a band structure with an exchange splitting of 0.37 eV for ferromagnetic Ni and zero splitting for paramagnetic Ni predicted peak position changes of 0.1 to 0.2 eV.