We report strong resonance enhancement in the 220-${\mathrm{cm}}^{-1\mathrm{}}$ Raman line of ${\mathrm{Cu}}_2$O at the ${{\Gamma }_{12}}^{-}$-phonon-assisted absorption threshold of the forbidden $1s$ yellow exciton. A consistent theoretical interpretation is presented. It shows that the line is due to scattering of two ${{\Gamma }_{12}}^{-}$ phonons and the resonance enhancement is strongly affected by the exciton lifetime. The latter effect has never been considered or observed before in resonance Raman scattering.

The magnetization of single crystals of Eu, Sm, Nd, Pr, and Pr-Nd alloys has been measured in fields up to 37 T (370 kG). The results give new information on the magnetic properties of these metals. Of particular interest is a first-order transition from a nonmagnetic to a metamagnetic phase in double-hexagonal close-packed Pr, due to the crossing of crystal-field levels, when a field of about 32 T is applied in the hard direction at low temperatures.

The effect of spin fluctuations on electrical resistivity $\rho \mathrm{}\left(T\right)\mathrm{}$ is studied in a single-band model. It is shown that $\frac{d\rho \mathrm{}\left(T\right)\mathrm{}}{\mathrm{dT}}$ varies as the magnetic specific heat for $T<\mathrm{}{T}_c$ as well as $T>\mathrm{}{T}_c$ and that both short-range and long-range correlations yield $\frac{d\rho \mathrm{}\left(T\right)\mathrm{}}{\mathrm{dT}}>0\mathrm{}$ for $T>\mathrm{}{T}_c$.

The Strutinsky method for extracting the shell corrections from Nilsson single-particle energies is tested consistently within the constrained Hartree-Fock (CHF) framework. It is shown that a Nilsson potential, fitted to the CHF single-particle energies at one deformation, reproduces the CHF level ordering at other deformation surprisingly well. The shell corrections obtained from the Nilsson single-particle energies via the Strutinsky method are shown, however, to be unreliable by 30% on the average.

The application and use of tensor polarized beams of deuterons in ($d, p\gamma$) angular correlation experiments with spin-0 targets is described in connection with the measurement of mixing ratios of decays from spin-$\frac{3}{2}$ states in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$.

We calculate the angular distribution and polarization of the photoneutrons from ${\mathrm{O}}^{16}$ in the giant-dipole region. We have to supplement our $E1\mathrm{}$ amplitudes, which were obtained previously, with large phenomenological $E2\mathrm{}$ amplitudes; we interpret this as evidence for a giant quadrupole resonance. We show that the importance of $E2\mathrm{}$ amplitudes makes the current data analysis in $E1\mathrm{}$ approximation very doubtful. The assumed $E2\mathrm{}$ resonance is also shown to be easily detected experimentally.

An examination of the foreign-gas pressure dependence of the intensity and spectrum of the signal from ${\mathrm{I}}_2$ vapor under off-resonance monochromatic excitation indicates that the re-emission process is not resonance Raman scattering as recently reported by Fouche and Chang.

A high-resolution electron time-of-flight spectrometer has been used in a transmission experiment to study resonances in $e$-${\mathrm{O}}_2$ scattering corresponding to vibrationally excited levels of the ${\mathrm{O}}_2^{-}$ ${}_{}{}^2{}_{}{}^{}\Pi _{\mathrm{g}}^{}{}_{}{}^{}$ ground state. A doublet structure, due to spin-orbit coupling, is observed. The fine structure of ${\mathrm{O}}_2^{-}$ is measured to be 0.020 ± 0.002 eV, and the energy of the center of the $v^{\prime }=4\mathrm{}$ resonance doublet is measured to be 0.091 ± 0.005 eV.

Electron energy-loss spectra have been obtained for ${\mathrm{N}}_2$ at 20.6 eV impact energy and scattering angles of 10°-138°. These spectra have been analyzed to yield the first identification of excitation to the $W{}_{}{}^3{}_{}{}^{}\Delta _{\mathrm{u}}^{}{}_{}{}^{}$, $w{}_{}{}^1{}_{}{}^{}\Delta _{\mathrm{u}}^{}{}_{}{}^{}$, $B^{\prime }{{}_{}{}^3{}_{}{}^{}\Sigma _{\mathrm{u}}^{}{}_{}{}^{}}^{-}$, and $a^{\prime }{{}_{}{}^1{}_{}{}^{}\Sigma _u^{}{}_{}{}^{}}^{-}$ states in electron impact spectroscopy, and the angular dependence of the excitations from 10° to 130°. The differential cross section for excitation of the $W{}_{}{}^3{}_{}{}^{}\Delta _{\mathrm{u}}^{}{}_{}{}^{}$ state is the largest triplet-state cross section at all scattering angles, and is the largest inelastic cross section section at angles greater than 70°.

A new afterglow analysis technique has been developed involving no assumption about the functional dependence (or lack of dependence) of the recombination rate coefficient on experimental parameters such as electron density or temperature. Explicit account is taken of the measured electron source term due to ionization during the afterglow. Preliminary results obtained at 295°K neutral temperature, at pressures from 20 to 30 Torr, at electron temperatures from 295 to 500°K, and over a limited range of electron densities near ${10}^{11}$ ${\mathrm{cm}}^{-3\mathrm{}}$ are in satisfactory agreement with collisional radiative recombination theories.

The Zeeman transition between the $M=\pm 1$ and $M=0\mathrm{}$ states of orthopositronium in its ground state has been observed in a solid for the first time, when positrons were stopped in a $\gamma$-${\mathrm{Al}}_2$${\mathrm{O}}_3$ powder pellet, thus providing strong evidence that essentially free orthopositronium exists in $\gamma$-${\mathrm{Al}}_2$${\mathrm{O}}_3$. The value for the positronium fine-structure interval is $\Delta \nu (\gamma -{\mathrm{Al}}_2{\mathrm{O}}_3)=203.308\mathrm{}\pm 0.024$ GHz (120 ppm). The difference $\Delta \nu \left(\mathrm{free}\mathrm{Ps}\right)-\Delta \nu (\gamma -{\mathrm{Al}}_2{\mathrm{O}}_3)$ is 88 ± 25 MHz.

In a previous report, we described a shifted spectral component in the light-beating spectrum of erythrocyte ghosts, and presented evidence suggesting that this component was related to the membrane active transport mechanism. Here, we describe the results of further studies which show that the shifted component does not derive from the active transport mechanism. Rahter, the shifted component is caused by convection in our cuvette, and appears in the homodyne spectrum because the light scattered from the incident beam mixes with that scattered from the beam which is reflected from the face where the beam exits from the cuvette.

The melting curve of pure ${\mathrm{He}}^3$ has been measured in the region of the "$A$" and "$B$" phenomena discovered by Osheroff, Richardson, and Lee. Within a 2% precision there is no effect of the "$A$" phenomenon on the slope of the equilibrium melting curve. This indicates that "$A$" is not related to the properties of solid ${\mathrm{He}}^3$. Also, we describe a new effect on thermal relaxation of a powdered-cerium-magnesium-nitrate thermometer immersed in ${\mathrm{He}}^3$.

A specific-heat "discontinuity" is observed in liquid ${\mathrm{He}}^3$ from 241 lb/${\mathrm{in}.\mathrm{}}^2$ to the melting pressure in the temperature range 2-3 mK.

Inelastic neutron scattering, used to study acoustic phonon linewidths in ${\mathrm{Nb}}_3$Sn, has revealed abrupt changes in certain phonon lifetimes in the vicinity of the superconducting transformation temperature, $T_c=18.3\mathrm{}°$K. This behavior arises because phonons with energy less than that of the temperature-dependent superconducting gap energy, $2\Delta \mathrm{}\left(T\right)\mathrm{}$, are energetically incapable of decaying by excitation of electron-hole quasiparticle pairs. These measurements give $2\Delta \mathrm{}\left(0\right)=4.4\mathrm{}{k}_{\mathrm{B}}{T}_c$ and reveal a strong anisotropy in the electron-transverse phonon interaction.

Critical exponents are calculated using conventional many-body perturbation theory by means of a self-consistent skeleton graph expansion in $4-\epsilon$ deminsions, where $\epsilon$ is small. The self-consistency is expressed through Ward identities. The results, the same as those of Wilson, are obtained without recourse to renormalization group arguments.

We treat the vacancy as a bubble of one atomic volume. We use empirical values of the surface tension measured for the metallic liquid phase to estimate the free energy of formation of this bubble. A small additive correction is made to account for covalent bonding in the semiconducting phase. The model is reasonable for cases where the Wigner-Seitz atomic radius is large compared with the dielectric screening length. Good agreement with experiment is found for available data for Si, Ge, and Sn.

Phonon pulse propagation has been studied in fused silica at frequencies between 0.4 and 2.0 GHz for temperatures as low as 0.1 K. An increase in attenuation, observed as the incident acoustic intensity is decreased, is attributed to resonant scattering by two-level "tunneling states" intrinsic to glasses.

High densities of excitons are produced in germanium at liquid-helium temperatures by a pulsed-laser pumping technique. The excitons condense into metallic droplets whose time decay, monitored by a cyclotron resonance method, is nonexponential and displays a cutoff. This is due to surface evaporation, and a measurement of the work function gives a value for the binding energy of the metallic liquid of $16\left(\{+3\mathrm{}\}\{-2\mathrm{}\}\right)$ K which agrees with the value we find from observation of the threshold for the liquid phase.

This paper introduces two integrals which simplify calculation of the dynamic properties of magnetic domains. These integrals, over quadratic functions of the spatial derivatives of the magnetization, yield forces acting on a domain which correspond to the gyroscopic and dissipative terms in the Gilbert equation. The force integral corresponging to the gyroscopic term is found to be even less sensitive to the details of the spin distribution than the dissipative drag integral. Hard magnetic bubble domains are considered as an illustrative example.