Measurements of the attenuation and velocity of pulsed high-frequency sound have been performed up to 133 MHz in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$. A new collective mode of the order parameter was discovered at a frequency extrapolated to $T_c$ of $\omega =(1.165\mathrm{}\pm 0.05){\Delta }_{\mathrm{BCS}}\left(T_c\right)$, where ${\Delta }_{\mathrm{BCS}}\mathrm{}\left(T\right)\mathrm{}$ is the energy gap in the weak-coupling BCS theory. The group velocity has been observed to decrease by as much as $\frac{2}{3}$ of the zero-sound velocity.

High-pressure x-ray scattering studies of $2H$-Ta${\mathrm{Se}}_2$ reveal reentrant behavior of the charge-density-wave (CDW) lock-in transition. As pressure is increased the normal-to-incommensurate CDW transition changes less than 5 K; however, the lock-in transition, initially suppressed to $T\to 0$ K at ∼1.7 GPa, reappears at ∼2.5 GPa. At the highest pressures (4.4 GPa) the temperature dependence of the incommensurability approaches the universal curve given by Landau theory for a single-$\overrightarrow{\mathrm{q}}$ CDW.

The temperature-dependent magnetic exchange splitting of an electronic surface state located at the $\overline{S}$ point of the Ni(110) surface Brillouin zone has been measured. The measured value of the splitting is 0.30±0.02 eV at 100 K which is equal to the exchange splitting of the bulk bands of Ni (0.31±0.04 eV) from which this surface state is derived. This result directly rules out the existence of a paramagnetic or magnetically "dead" surface layer on Ni(110).

For a simple nontrivial model potential, the full quantum mechanics of the Bloch electrons in rational magnetic fields is reduced to a one-dimensional eigenvalue problem and the exact diamagnetic band structure is calculated from first principles. Agreements with and deviations from the predictions of the semiclassical Onsager dynamics are found and discussed.

The temperature ($T$) dependence of the width of the first ionization potential of condensed films of isopropyl benzene has been measured by ultraviolet photoelectron spectroscopy with use of synchrotron radiation. Over the range $15°\mathrm{K}<~T<~150°\mathrm{K}$, the linewidth exhibits the form ${\delta }^2\mathrm{}\left(T\right)={\delta }^2\mathrm{}\left(0\right)+c^{2}T$, where $c=4.4\mathrm{} (\pm 0.8)\times {10}^{-2\mathrm{}}$ eV/${\left(\mathrm{°}\mathrm{K}\right)}^{\mathrm{½}}$. This $T$ dependence originates from the interaction of the photogenerated localized molecular hole states with low-energy vibrational modes of the film.

The first discussion of a long-wavelength, magnetostatic, surface spin-wave mode on uniaxial antiferromagnets is presented. In the absence of an applied field, the frequency of the surface wave depends on the angle between the direction of propagation and the easy axis. With a magnetic field applied parallel to the surface, and along the easy axis, the surface mode does not propagate in all directions, but is limited to a restricted set of angles.

The longitudinal electrical and thermal magnetoresistivities (${\rho }_{\mathrm{zz}}$ and ${\gamma }_{\mathrm{zz}}$) of potassium have been simultaneously measured at fields up to 7.5 T and at temperatures of 2-4 K. Although ${\rho }_{\mathrm{zz}}$ is linear in field, ${\gamma }_{\mathrm{zz}}$ saturates; this behavior is in agreement with recent predictions of models based on the presence of voids.

A local-orbital formulation of the Dyson equation is presented for the one-particle Green's function with the self-energy expressed in terms of a dynamically screened interaction which includes local-field and excitonic effects. Also presented is a quantitative calculation of the quasiparticle states for diamond from first principles, which demonstrates the different roles played by two-particle excitations (electron-hole, plasmon). A discussion of the implications for local-density and empirical one-electron concepts is given.

An optically detected NMR measurement of the hyperfine tensor for an excited state of an impurity rare-earth ion (${\mathrm{Pr}}^{3+}$) in a solid (LiY${\mathrm{F}}_4$) is reported. The results have been used to obtain for the first time a measured value of the hyperfine interaction constant $A_j=616\mathrm{}\pm 51$ MHz of the ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ excited state. This is somewhat smaller than the calculated value of 754 MHz.

Raman scattering from folded longitudinal phonons in a GaAs-AlAs superlattice is observed, and the resonant behavior for laser frequencies near the gap of this sample is studied. A quantitative explanation of the data is given in terms of a simple theory which involves the Kronig-Penney model for the electrons and considers the phonons in the elastic continuum limit.

The special relativistic transformation of temperature is not known with certainty and some authors believe it to be arbitrary within a certain range of possibilities. A procedure is proposed here which can in principle, and for the first time, lead to an experimental attack on this problem. Even though the experimental difficulties may be prohibitive, if the principle of the method is granted, then a definite transformation must exist.

Conservative Hamiltonian systems with two degrees of freedom are discussed where a typical trajectory fills the whole surface of constant energy. The trace of the quantum mechanical Green's function is approximated by a sum over classical periodic orbits. This leads directly to Selberg's trace formula for the motion of a particle on a surface of constant negative curvature, and, when applied to the anisotropic Kepler problem, yields excellent results for all the energy levels.

It is shown that in the turbulent regime of systems with period-doubling subharmonic bifurcations, the maximum Lyapunov characteristic exponent behaves like $\overline{\lambda }={\overline{\lambda }}_0{(\mathcal{r}-{\mathcal{r}}_c)}^t$, with $t$ a universal exponent which is calculated to be $t=0.449\mathrm{}8069\dots$. This result is in agreement with the available data on $\overline{\lambda }$ for a number of dynamical systems.

Quark structure functions have been extracted from low-$p_T$ inclusive hadron production data for the pion and kaon with use of the recombination model. $n^{\pi }=1.0\mathrm{}\pm 0.1$ and $n^K=2.5\mathrm{}\pm 0.6$ is obtained, where $n$ is the leading ($1-x$) power of the nonstrange-valence-quark distribution. Both the pion and kaon nonstrange-sea-quark functions have $n\simeq 3.5$.

In O$\mathrm{}\left(N\right)\mathrm{}$ extended supergravity theories, the usual arguments for one-loop finiteness (modulo topological terms) cease to apply when the internal symmetry is gauged because of the appearance of a cosmological constant related to the gauge coupling $e$. For $N<~4$, we find that infinite renormalizations are required. Remarkably, the particle content of theories with $N>\mathrm{}4\mathrm{}$ results in a cancellation of these infinities, implying, in particular a vanishing one-loop $\beta \mathrm{}\left(e\right)\mathrm{}$ function.

Fusion cross sections measured at high energies are parametrized in terms of a "statistical yrast line." This line lies parallel to the usual yrast line (given by the rigid-body moment of inertia, $\frac{2}{5}M{{\mathcal{r}}_0}^2{A}^{\frac{5}{3}}$) but is shifted upward by an additional energy $\Delta Q$. Most experimental fusion cross sections for systems with $A\lesssim 80$ are well reproduced with values of ${\mathcal{r}}_0=1.20\mathrm{}\pm 0.05$ fm and $\Delta Q=10\mathrm{}\pm 2.5$ MeV.

Seven differential cross sections of the reaction $p+d\to {}_{}{}^3{}_{}{}^{}\mathrm{He}+\gamma$ have been measured at $T_p=450\mathrm{} \mathrm{and} 550$ MeV between 52° and 92° (${\theta }_{\gamma }$ c.m.). ${}_{}{}^3{}_{}{}^{}\mathrm{He}$'s were analyzed by the SPES I spectrometer in coincidence with photons detected by Cherenkov counters. The results are about twice the cross sections of the inverse reaction measured recently by Hegerath et al. and by Argan et al. The data are consistent, however, with the $\gamma +{}_{}{}^3{}_{}{}^{}\mathrm{He}\rightleftarrows p+d$ data of Heusch et al.

Transition-energy correlations are studied in rotational erbium nuclei up to 1250 keV. A collective moment of inertia ${\mathcal{I}}_c$ corresponding to in-band transitions is directly deduced from the data and compared to the effective moment of inertia, ${\mathcal{I}}_{\mathrm{eff}}$, deduced from multiplicity measurements. For $I\sim \mathrm{}(30-45)\mathrm{}\hslash$ it is found that ${\mathcal{I}}_c$ is 25-50% smaller than ${\mathcal{I}}_{\mathrm{eff}}$, which suggests an important contribution to the total spin from a few aligned particles. This description implies band crossings for which there is independent evidence.

The mean charge, $\overline{q}$, has been measured for projectiles $5<~Z_1<~26$ exiting thin carbon foils at velocities $0.8<~\frac{v}{v_0}<~1.0$. It is observed that $\overline{q}\left(Z_1\right)$ increases strongly with $Z_1$ with a broad peak occurring at $Z_1\sim 15$. It is shown that much of the enhancement can be accounted for by post-foil Auger decay of projectile inner-shell vacancies.

Shapes and stability of surface-tension-endowed drops rotating rigidly at fixed angular momentum are calculated by finite-element analysis. A new family of asymmetric two-lobed drop shapes is discovered that branches from, and rejoins, the Pik-Pichak family of symmetric two-lobed shapes. The computations are verified for axisymmetric and symmetric two-lobed drop shape by comparison with previous approximations.