Making use of a model Hamiltonian which includes, in addition to the pairing interaction, the spin-exchange interaction as well as the dipole interaction, we calculate explicitly the dynamical spin susceptibility of the Anderson-Morel state. It is shown within the random-phase approximation that the spin susceptibility has simple poles, which give rise to the nuclear magnetic resonance in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The result is compared with a recent phenomenological theory by Leggett.

We have experimentally determined the equation of state of a two-dimensional "gas" of pentadecylic-acid molecules moving on the surface of water. Our data provide conclusive evidence for the occurrence of a phase transition in this two-dimensional system, similar to the liquid-vapor transition displayed by three-dimensional pure fluids. We have demonstrated the existence of a critical point, determined the shape of the coexistence curve, and observed an increase in the isothermal compressibility near the critical point.

We have made the first quantitative experimental study of transient self-focusing in a Kerr liquid by propagating $Q$-switched laser pulses in an isotropic nematic substance which has a long orientational relaxation time. Our results show good qualitative, and occasionally quantitative, agreement with the existing theoretical calculations.

A theoretical model is proposed in relation with the observed lack of electron runaway processes in magnetically confined, high-electron-temperature plasmas on which electric fields of the order of or larger than the critical runaway field have been applied. The excitation of standing modes locked in with the periodic inhomogeneities of the magnetic field is considered in order to provide, via mode-particle resonance processes, a momentum exchange between the (accelerated) current-carrying electrons and the magnetic field itself.

Comparison of ultraviolet-photoemission, valence-orbital spectra (as well as high-resolution, x-ray photoemission, N-core-level spectra) of TTF-TCNQ, neutral TCNQ, and ${\mathrm{K}}^{+}$ ${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}^{-}$ indicates a large amount of charge transfer in TTF-TCNQ. The spectra for this complex show strong coupling between states near the Fermi energy and molecular vibrations due to localization of the mobile electrons on individual molecules, at least on the time scale of bond vibrations.

The heat capacity of amorphous germanium, measured between 2 and 30 K using a thermal-relaxation technique, is about 50% greater than that of crystalling germanium, but has a similar temperature dependence. We infer an amorphous phonon density of states at low frequencies given by the TA crystalline density of states, broadened, and with all modes reduced in frequency by a factor of 0.84. A re-examination of Raman measurements in amorphous germanium shows them to be consistent with this result.

Iron-57 Mössbauer absorption measurements and computer calculations show the crystalline electric field to be sharply defined in amorphous metals and alloys. Above the Curie point of amorphous rare-earth-iron compounds we observe a well-defined quadrupole splitting, but in the ferromagnetic phase there is no spectroscopic structure. Computer calculations based on a recent model of the magnetism of rare-earth-transition-metal compounds yield both the paramagnetic doublet and the ferromagnetic flat spectrum.

We show that an external field in dysprosium aluminum garnet (DyAlG) couples not only to the magnetization, but also to the staggered magnetization, in a term linear in that order parameter. Neutron-scattering experiments are interpreted from this viewpoint. Reconsideration of the phase diagram of DyAlG leads to the conclusion that the previously reported tricritical point is, in fact, a wing critical point. Production of a staggered field should be possible in a class of compensated antiferromagnets.

With the mass asymmetry described by the dynamical collective fragmentation coordinate $\xi$, and with use of the asymmetric two-center shell model, the fission mass distributions for ${}_{}{}^{226}{}_{}{}^{}\mathrm{Ra}$, ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$, and ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$ (which are typical representatives for triple-, double-, and single-humped distributions) are explained.

The inelastic scattering of 115-MeV $\alpha$ particles from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ shows an enhancement of the continuum at about 18.25 MeV excitation energy. This observation supports recent electron, proton, and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ scattering analyses which ascribe similar enhancements at $E_x\approx \frac{63}{A^{\frac{1}{3}}}$ MeV to an isoscalar giant quadrupole resonance. Although contributions from a monopole excitation cannot be ruled out, attributing all observed yields to a giant quadrupole resonance exhausts only 32% of the energy-weighted sum rule.

In critical or nearly critical heavy-ion collisions, induced as well as spontaneous energyless $e^{-}{e}^{+}$ pair creation result in the decay of the neutral vacuum. Induced transitions from the negative-energy continuum into a vacant molecular $1s$ level can occur even in the absence of diving and produce a substantial enhancement and broadening of the previously considered spontaneous positron spectrum. Total cross sections of 5 b have been calculated for U-U collisions.

The effect of the Pauli principle on the low-energy pion-nucleus interaction is examined. We find that the Pauli effects do not appreciably alter the estimate of the strength of the $p$-wave optical potential based on free-space scattering volumes.

Nuclear finite size correction to the vacuum polarization is examined and applied to muonic atom spectrum. An analytic expression for the potential due to this correction is given. It increases the present discrepancy by 5 eV in the $5g_{\frac{9}{2}}-\mathrm{to}-4f_{\frac{7}{2}}$ transition in lead.

We have calculated the change in the vacuum polarization for muonic atoms with a high-$Z$ nucleus arising from the finite extent of its charge distribution. In the calculation, the electron mass is set equal to zero and only the first term in an expansion in (nuclear radius)/(radius of the muonic state) is retained. The calculation is done to all orders in $Z\alpha$ and a simple closed-form result is obtained.

It has been suggested that elementary particles should be associated with the irreductible representations of the Bondi-Metzner-Sachs group, on the grounds that in these, only discrete spins appear. We emphasize that the last statement strongly depends on the topology originally chosen for supertranslations, and we discuss in some detail how continuous spins appear when other equally reasonable topologies are chosen, which depend in a more explicit way on the smoothness of supertranslations.

It is shown that the energy shift of $K$ x rays emitted by an atom doubly ionized in the $K$ shell comprises a 16% Breit-interaction contribution for $Z=81\mathrm{}$ and thus constitutes a sensitive test of these corrections. The calculated shift of the $K{\alpha }_1$ line agrees with the present experiment (1160 ± 70 e V). This invalidates the much larger 2100-e V shift, reported by another group, which appears to be due to spurious effects.

The Raman and Brillouin processes have important sharp-threshold parametric instabilities that afford explanations of long-standing anomalies in stimulated-scattering and self-focusing experiments. Below the threshold intensity $I_c$, the gain is nonexponential and greater than that of previous theories of stimulated scattering, and at the threshold the Stokes intensity increases nearly discontinuously. Typically, $I_c\sim {10}^9$ W/c${\mathrm{m}}^2$ for a number of gases, liquids, and solids. The theoretical results agree well with previous experimental results.

We propose the heating of collisionless plasma by utilizing a spatial phase mixing by shear Alfvén wave resonance and discuss the application to toroidal plasma. The phase mixing takes place as a result of the nonuniform Alfvén speed. The approximate heating rate per cycle of the wave frequency is given by $\frac{\left(\frac{b_0^{}{}_{}{}^2}{{\mu }_0}\right)\kappa }{k_{\perp }}$ where $\kappa$ is the measure of the nonuniformity, $k_{\perp }$ is the wave number perpendicular to the direction of the magnetic field and the nonuniformity, and $b_0$ is the flux density of the applied-wave magnetic field.

This one-dimensional model exhibits a strong spatial collapse of the electric field when the self-consistent pump amplitude is held constant. The linear instability saturates if one allows for the self-consistent modification of the pump due to nonlinearities. The saturated state is characterized by relaxation oscillations and spatially localized electric fields of finite amplitude.

The exact transition temperature and the order of phase transition are determined for a vertex model in three dimensions. The transition is in general of first order with a latent heat and occurs in a limited region in the parameter space. Details of the region depend on the underlying lattice and differ significantly between lattices with high (fcc and bcc) and low (simple cubic and diamond) coordination numbers.