Using neutron spectrometry we have investigated the magnon dispersion relation for the ferrimagnetic cubic Laves compound ${\mathrm{Ho}}_{0.88}$${\mathrm{Tb}}_{0.12}$${\mathrm{Fe}}_2$ at room temperature and 12 K. The results are described surprisingly well by a very simple near-neighbor exchange model which includes only iron-iron and iron-rare-earth interactions, crystal field anisotropy, and temperature renormalization that is derived from the sublattice magnetization.

A relativistic wave equation is solved for equal-mass quarks interacting via a combined linear and "Coulombic" potential, the latter being softened at short distances in accord with asymptotic freedom. Assuming that colored SU(4) is broken only by the quark mass differences, I predict masses and leptonic decay widths for the $\rho$, $\varphi$, and $\psi$ meson families of states. Agreement with experiment is excellent.

The angular distribution for deeply inelastic scattering of ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at laboratory energies of 494, 510, and 718 MeV exhibits a strong peak that moves forward and sharpens with increasing energy. Forward peaking never becomes prominent. The integrated cross section is nearly equal to the total absorption cross section at all energies. These results are inconsistent with a unique critical radius for fusion and are in contrast to those for systems with lower $\frac{Z_1}{Z_2}$ product.

A large cross section for inelastic collision is induced by an incident laser tuned to the frequency of the interatomic energy defect. We study energy transfer from the Sr $5p{}_{}{}^1{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}$ level to the Ca $4d{}_{}{}^1{}_{}{}^{}D$ level and measure a cross section for inelastic collision of 3×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at a laser power density of 8.6×${10}^6$ W/${\mathrm{cm}}^2$ and a wavelength of 6409.0 Å.

Suppression of the $m=1\mathrm{}$ growing mode of a screw pinch is obtained by feedback stabilization. The transverse field produced by $l=1\mathrm{}$ windings is automatically controlled by the magnetically detected plasma motion, in order to create a restoring force for both displacement coordinates.

Measurements of electron density and x-ray emission have been made on a C VII plasma, generated by a 9×${10}^{12}$-W-${\mathrm{cm}}^{-2\mathrm{}}$ C${\mathrm{O}}_2$ laser beam. A density cavity and x-ray filamentation are observed. The relevance of these results to theories of resonance absorption, soliton formation, self-modulation, and filamentation of laser light is noted.

By use of a small launcher in an ion-beam—plasma system, a spatially growing mode, which propagates obliquely to the ion beam, was observed. With ion beams, the wave propagation vector was found to be not in the radial direction from the launcher. The observed phase velocity and spatial growth rate of a slow ion-beam—plasma mode are explained by three-dimensional wave theory.

A simulation model has been developed to study the low-frequency trapped-particle instability in a linear geometry. Low-frequency drift instabilities identified as the dissipative trapped-electron modes grow, accompanied by the turbulent transport of plasma. Measured electron heat conductivity is a few times larger than the particle diffusion constant.

A $T^{\frac{3}{2}}$ contribution to the low-temperature specific heat of the ferroelectrics triglycine sulfate, potassium dihydrogen phosphate, BaTi${\mathrm{O}}_3$, and LiNb${\mathrm{O}}_3$ is reported. This may be a domain-wall contribution because it is not present in paraelectrics or antiferroelectrics.

Application of the technique of forced thermal light scattering allowed the observation of second sound in NaF in spite of the extremely weak coupling between light and thermal fluctuations. The velocity and damping were measured up to 23 K. These measurements extend the results of previous heat-pulse experiments in agreement with theory.

By correct reduction of some quartic forms in fermion field operators, I eliminate all but a constant and some quadratic terms. I can use this to transform the Wolff model, of a magnetic impurity in a nonmagnetic metal, into a solvable quadratic form in fermions. Applying the same method (with less justification) to Hubbard's model in three dimensions, I obtain an oversimplified but nevertheless suggestive, and diagonal, Hamiltonian.

The velocity spectrum of ${\mathrm{Cs}}^{+}$ and ${\mathrm{Br}}^{-}$ ions emitted from thin CsBr films irradiated with fission fragments show that the ions are not ejected by direct collisional interactions with the fission fragments but appear to be thermionically emitted with an average temperature of 6.6 × ${10}^4$ K. This suggests the existence of a transient hot thermal core within the fission fragment track. Transient fission tracks in condensed phases may be convenient media for studying fast high-temperature atomic and molecular interactions.

The question of $C$, $P$, and $T$ nonconservation in gravity is reexamined, and feasible experiments are suggested to test these effects.

The decay rate of orthopositronium is found to depend linearly on the mass per free volume in powders of Si${\mathrm{O}}_2$ with grain radii of 35 and 70 Å. Three data points have a decay rate significantly less than both the theoretical free-space decay rate and the results of previous experiments. The value of ${\lambda }_3$ extrapolated to zero density, 7.104±0.006 μ${\sec }^{-1\mathrm{}}$, is (1.9±0.1)% below the theoretical value of the free-space lifetime. Possible interpretations of these results are discussed.

In an attempt to confirm the charm interpretation of dimuons, we have constructed an explicit quark-parton model for the production and decay of a new hadron in neutrino interactions. The model produces, among other results, a distribution for the muon energy ratio $\frac{E\left({\mu }^{+}\right)}{E\left({\mu }^{-}\right)}$, which is independent of the neutrino spectrum and in remarkable agreement with observations. The model encourages the hope that the study of dimuon characteristics could reveal the charge of the charmed quark and the chirality of the charmed current.

We have observed the decay $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\eta$ with a branching fraction of (4.3±0.8)%. This measurement, together with previous measurements of $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)+\mathrm{anything}$, $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}{\pi }^{+}{\pi }^{-}$, and $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\gamma \gamma$, indicates that isospin is conserved in the decay $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\pi \pi$ and establishes the isospin and $G$ parity of the $\psi \mathrm{}\left(3684\right)\mathrm{}$ to be $I^G=0^{-}$.

The total fusion cross section for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ system has been measured in the ranges $13 \mathrm{MeV}<~E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~27 \mathrm{MeV}$. The cross section is found to increase with bombarding energy up to $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}\approx 17$ MeV but to stay roughly constant at higher energies, in qualitative agreement with predictions of current models. Superimposed on this average cross-section behavior we observe unexpected oscillations with a period of about 3-4 MeV (c.m. energy).

We have measured the predicted orientation induced by first-order Stark effect on $\mathrm{sp}$ coherent levels of ${\mathrm{He}}^{+}$ and H excited by a 100-keV ${\mathrm{Na}}^{+}$ beam impinging on a cell filled with He or ${\mathrm{H}}_2$. We discuss the mechanism of production of $\mathrm{sp}$ coherence by dissociative excitation of ${\mathrm{H}}_2$.

The vibrational motion of Sn in the high-critical-field superconductor Sn${\mathrm{Mo}}_6$${\mathrm{S}}_8$ has been studied with the ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ Mössbauer effect. The Mössbauer thermal shift and recoil-free fraction are found to contain large anharmonic contributions from the soft modes. The soft vibrational motion contributes substantially to the mass enhancement $\lambda$.

The critical properties of the model of a spin-glass proposed by Edwards and Anderson are studied using the renormalization group. The critical exponents are calculated in $6-\epsilon$ spatial dimensions. It is argued that a tricritical point can exist where the nonordering field is the skewness of the distribution of $J$.