We propose a description of collective quadrupole states in even-even nuclei in terms of representations of a boson SU(6) group. We show that within this model both the vibrational and the rotational limit can be recovered.

A uniform semiclassical $S$ matrix has been developed for collisions of charged particles with rotating rigid dipoles, with use of first-order perturbation theory. The resulting expression is analytical, depending on tabulated functions, and trivial to calculate; it allows evaluations of quantum transitions in classically forbidden regions, and of quantum interference effects.

It is shown that Brillouin scattering of intense laser light in plasmas can be limited by momentum and energy deposition as a result of reflection of the light. The calculations compare favorably with some recent experimental results.

A new model for time-dependent and steady-state ion and electron flow in large-aspect-ratio diodes is constructed. The electron trajectories are computed with use of the self-consistent fields calculated during the initial ion motion. The dynamic formation of a tightly pinched electron flow is qualitatively explained. Very large ion currents, nearly equal to the electron current, are predicted for flat solid cathodes, when steady-state flow is achieved.

Using the time-of-flight technique, energy distribution measurements were made of the $\alpha$ particles emitted from laser implosions of DT gas in glass microshells. The number of nuclear reactions was determined by an absolute measurement of the number of $\alpha$ particles. From the width of the energy distributions, upper limits of the plasma ion temperature have been inferred.

The alignment of impurity nuclei recoil-implanted into copper has been measured as a function of temperature. At 300 K, ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{67}{}_{}{}^{}\mathrm{Ge}$ impurities lose 50% of the nuclear alignment within ${10}^{-8\mathrm{}}$ sec after implantation into the copper host, while the full alignment is observed for the ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$ impurity. The temperature dependence of the alignment can be explained by a simple model which assumes static quadrupole interactions with lattice defects in the vicinity of the impurity.

The resonant Jahn-Teller coupling of the $B_{2\mathrm{g}}$ acoustic phonon and the Zeeman-split ground doublet in TmV${\mathrm{O}}_4$ has been studied by inelastic neutron scattering. Tuning of the magnetic field provides a means for investigating the wave-vector dependence of the interactions. We find that the coupling is constant in the region where the phonon dispersion is linear, up to 0.4 of the distance to the zone boundary. This agrees with the predictions of a Debye model.

A convergent perturbation scheme known as the layer-doubling method is used to determine the chemisorption position and bond length of an oxygen $p(2\mathrm{}\times 1)$ overlayer on W(110) surface. The use of perturbation treatment allows accurate and economical determination of surface crystallography on this strong-scattering material. Using eight phase shifts and 89 beams in the calculation, the oxygen atoms are found to occupy threefold-coordinated binding sites with a bond length of 2.08 Å.

Submillimeter photoconductivity in doped germanium has been studied with a lamellar grating spectrophotometer. The observed photoconductivity is ascribed to a shallow trapping state such as $D^{-}$ or $A^{+}$. However, our spectral peak energies and shapes are quite different from those previously reported by Gershenzon, Gol'tsman, and Mel'nikov.

A full series of combined cyclotron- and spin-resonance transitions is observed in magnetophonon oscillations in $n$-InSb under hot-electron conditions. These originate from the emission of LO phonons. Probabilities of combined resonances induced by polar and nonpolar coupling with optical phonons are calculated for the spin-orbit interaction mechanism.

The temperature-dependent impurity susceptibility for the symmetric Anderson Hamiltonian is discussed for all physically relevant values of its parameters $U$ (the Coulomb correlation energy) and $\Gamma$ (the $d$-level width). For $U>\mathrm{}\pi \Gamma$, the results, for temperatures less than $\frac{U}{10k_B}$, map onto those of the spin-½ Kondo Hamiltonian with an effective exchange constant given by $\rho J_{\mathrm{eff}}=-\frac{8\Gamma }{\pi U}$. At higher temperatures the results show the formation of the local moment from the free orbital.

Molecules diffracted from a crystal can exchange energy between translation and rotation. Such an interchange can lead to an extremum in the scattering angle as a function of the incident wavelength; this in turn concentrates scattered intensity at the extremal angle, causing a singularity in the differential cross section. Extremal scattering in rotationally inelastic collisions is explored quantitiatively for the diffraction of hydrogenic molecules and shown to affect significantly experiments with thermal beams.

We report the first experimental determination of the orientation of the main axes of the constant-energy ellipsoids of the secondary valence-band extrema of PbTe. These extrema are generally believed to be located at the $\Sigma$ point of the Brillouin zone. Investigation of the anisotropic behavior of the coefficient of the conductivity of warm holes shows that the main axes of these ellipsoids are parallel to $〈100〉$ and do not coincide with the symmetry direction of the $\Sigma$ point.

A new class of exact standing-wave solutions of the Maxwell cold-plasma equations with fixed ions is described. The waves are transverse, and circularly polarized. These solutions permit an analytical treatment of intense wave penetration into inhomogeneous plasmas with fixed ions.

From the intensity and Rayleigh linewidth of light scattered by the system Ne-Kr near the temperature minimum of the critical line (double plait point), we have verified the phenomenological rule that, for constant overall composition, the critical exponents are independent of the path of approach to the critical line, except along a path which is asymptotically parallel to the critical line where they assume twice their usual values.

The general features of $T_1\left(\omega \right)$ data on dilute ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are explained in terms of coupled rotation-translation motions of ${\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)}_2$ molecules bound together by the elastic ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ interaction. As the concentration of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is lowered the molecular motions become two-dimensional and give rise to the anomalous structure observed in the $T_1\left(\omega \right)$ spectrum.

Experiments based on an analogy to the ac Josephson effect have shown in both ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ that a pairing theory of the superfluidity of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is essentially correct. Additional observations of parallel ringing are not in agreement with the simple "pendulum models" used to describe nonlinear dynamic magnetic effects.

A new interferometric method of measuring $\Delta n$, the variation of refractive index of liquids with pressure, to 14 kbar is described. The results obtained on $\Delta n$ versus pressure up to the freezing point of water and carbon tetrachloride at room temperature are presented and discussed.

It is shown that in ferromagnets, an antisymmetric Dzialoshinsky-Moriya interaction will introduce an additional phase shift (dynamical canting) between spins in their spinwave precession motion. This phase shift will have a most pronounced influence on the resonance intensities of the standing spin-wave mode in a thin film of a material having such an interaction.

We have investigated the effect of temperature on the cyclotron resonance of electrons in an inversion layer on (100) Si between 4 and 80 K. With increasing temperature the resonance line is found to broaden and to shift considerably to higher resonance fields. The latter effect is strongest at low electron densities and, if interpreted as due to a temperature-dependent effective mass ${m_c}^{*}$, corresponds to changes in ${m_c}^{*}$ in excess of 50%.