Isochoric pressure measurements have been made in bcc solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ from the melting point down to 29 mK in magnetic fields up to 8.0 T and for molar volumes of 23.834, 24.163, and 24.371 ml/mole. The measurements show that the pressure at high magnetic fields is thermodynamically inconsistent with reported values for the Weiss temperature deduced from nuclear magnetic susceptibility. Furthermore, the Weiss temperature deduced from our data at 24.25 ml/mole is in disagreement with that used in the theory of Roger, Hetherington, and Delrieu.

A gas of 99.8% electron- and nuclear-spin-polarized hydrogen has been prepared. The surface and volume nuclear relaxation rates have been measured and the magnetic field dependence ${(1+\frac{16.68}{B})}^2$ has been confirmed. The ratio of the surface recombination rate constants for collisions between atoms in hyperfine states, $a-a$ and $a-b$, is measured to be 2.23(25). Nuclear relaxation on the surface has been suppressed by using ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ to make an atomically flat surface.

It is demonstrated that for a vector spin-glass in a magnetic field, replica-symmetry breaking, the theoretical indicator for magnetic irreversibility, occurs simultaneously with transverse spin-glass ordering as the temperature is reduced. It is argued that the irreversibility onset will be strong in the transverse direction, but only weak longitudinally, with a crossover to strong longitudinal irreversibility at a lower temperature.

The influence of magnetic impurities on weak localization is investigated. Thin Mg films are covered with $\frac{1}{1000}$ monolayer of Fe. A temperature-independent magnetic scattering time ${\tau }_s=4.7\mathrm{}\times {10}^{-12\mathrm{}}$ sec is obtained.

A magnetic-field-induced exchange stiffness and dispersion have been observed in the spin-flip Raman Spectra of localized donor electrons in $n$-type CdS, a model amorphous antiferromagnet. At high applied fields, there is a $q$-dependent shift in the peak position of the Stokes line. With increasing field, the peak and spectral weight of the excitations move to the low-energy side of the Zeeman energy as $q$ increases. This negative dispersion is consistent with the antiferromagnetic coupling.

The first discussion of the nonlinear mixing of bulk and surface magnetostatic spin waves is presented. The unusual property of these waves—that the frequency is dependent on the direction of propagation and not the magnitude of the wave vector—allows resonant generation of a new wave if the propagation directions of the two incident waves are properly chosen. In addition to the mixing of two bulk (or surface) waves to produce a new bulk (or surface) wave, the mixing of two bulk waves to produce a resonantly enhanced surface wave is discussed.

Existing theoretical models are unable to account for a number of important optical properties of oxygen in GaP. In this paper an energy-level structure is proposed which explains in detail the optical spectra in terms of spin- and $k$-conserving one-electron transitions. This scheme is based on spin multiplets formed from the neighboring gallium orbitals, which interact only weakly with a neutral O atom. Its striking success exposes limitations of more conventional single-particle theories.

Oscillations of the steady-state rate of catalytic CO oxidation on clean Pt surfaces were observed under low-pressure conditions and are related to the adsorption properties of the reactants. Evidence is presented for a model in which the reversible (5×20)⇄(1×1) phase transition of the Pt(100) surface (which is associated with a marked variation of the oxygen sticking coefficient) is responsible for the oscillations.

Expressions are given for the friction force and velocity autocorrelation function of a hard-spherical Brownian particle with "stick" boundary conditions in a fluid with internal rotational degrees of freedom. The velocity autocorrelation function is found to have a $t^{-\frac{3}{2}}$ tail. Comparison with recent experiments indicates that rotational transport coefficients may be measurable by means of light-scattering experiments on Brownian particles. Preliminary estimates are given for rotational transport coefficients of water.

An exact Monte Carlo method for calculating thermodynamic properties of quantum spin systems is described. Results for one-dimensional ferromagnetic and antiferromagnetic systems and for three-dimensional ferromagnetic systems show that the method can be used to study quantum spin systems as extensively as classical spin systems are studied with conventional Monte Carlo methods.

The linear-polarization correlation of pairs of photons emitted in a radiative cascade of calcium has been measured. The new experimental scheme, using two-channel polarizers (i.e., optical analogs of Stern-Gerlach filters), is a straightforward transposition of Einstein-Podolsky-Rosen-Bohm gedankenexperiment. The present results, in excellent agreement with the quantum mechanical predictions, lead to the greatest violation of generalized Bell's inequalities ever achieved.

It is shown experimentally that a bistable system is driven by a suitable external modulation to a region of random intermittency which displays a low-frequency power-law divergence. This low-frequency divergence is associated with a topological alternation between two strange attractors in phase space, either unsymmetric or fully symmetric depending on whether the two potential valleys are differently or equally located. This picture seems sufficiently general to apply to most cases of low-frequency noise currently reported.

From 12000 charged-current ${\nu }_{\mu }$ D events obtained in an exposure of the Fermilab 15-ft bubble chamber to a high-energy wide-band neutrino beam, the absolute neutrino flux is determined using the reaction ${\nu }_{\mu }n\to {\mu }^{-}p$. For the total charged-current cross section, ${\sigma }_t=k{E}_{\nu }$, $k=(0.68\mathrm{}\pm 0.04\pm 0.10)\times {10}^{-38\mathrm{}}$ ${\mathrm{cm}}^2$/GeV is obtained for $E_{\nu }$ between 10 and 200 GeV. No clear energy dependence of the slope parameter $k$ is observed.

A fully microscopic analysis of the experimentally observed $1^{+}$ and $7^{+}$ ($p, n$) cross sections in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ is presented. Subnuclear $\Delta$-isobar degrees of freedom are treated explicitly in both the structure and reaction calculation. It is shown that the quenching due to the $\Delta$ isobars depends on the multipolarity of a given state.

A relativistic description of deuteron elastic scattering based on a two-particle Dirac Hamiltonian containing phenomenological nucleon-nucleus Dirac potentials is developed. The resulting effective central potential is like that obtained with a folding model based on the Schrödinger equation; the spin-orbit potential, however, is only one-half as strong. Dirac and Schrödinger fits to 80-MeV $d$+${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ data with potentials consistent with nucleon-nucleus phenomenology are of comparable quality.

The parities of eleven $J=1\mathrm{}$ levels in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ were determined by nuclear resonance fluorescence scattering of linearly polarized photons. A new $1^{+}$ level at $E_x=5.846\mathrm{}$ MeV with $\frac{{{\Gamma }_0}^2}{\Gamma }=1.2\mathrm{}\pm 0.4$ eV was found. This level can probably be identified with the theoretically predicted isoscalar $1^{+}$ state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. All other bound dipole states below 7 MeV with $\frac{{{\Gamma }_0}^2}{\Gamma }>1.5\mathrm{}$ eV have negative parity. The $1^{-}$ assignment to the 4.842-MeV level is of special significance because of previous conflicting results about its parity.

Competition between third-harmonic generation and multiphoton ionization in xenon is confirmed in a direct experiment using counterpropagating circularly polarized laser beams to suppress third-harmonic emission. Three-photon resonantly enhanced multiphoton ionization through the $6s$ and $6s^{\prime }$ levels in xenon, previously reported to disappear at pressures above a few Torr, gives rise to sharp intense ionization signals under these conditions.

By directly observing the nuclear polarization of ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$, the efficiency $\eta$ of spin exchange between optically pumped Rb spins and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ nuclei has been measured. It is found that $\frac{1}{\eta }=23\mathrm{}\pm 4$ rubidium $D_1$ resonance-line photons are required to polarize a ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ nucleus when long-lived van der Waals molecules are unimportant. The binary spin-exchange cross section deduced from our measurements is ${\sigma }_{\mathrm{ex}}=(7.3\mathrm{}\pm 1.1)\times {10}^{-21\mathrm{}}$ ${\mathrm{cm}}^2$.

Photoelectron spectra for the three-photon resonant, five-photon ionization of NO via the $v^{\prime \prime }=0\mathrm{}$ level of the $C{}_{}{}^2{}_{}{}^{}\Pi \left(3p\pi \right)$ Rydberg state show that N${\mathrm{O}}^{+}$ ($X{}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$) is formed primarily in $v^{\prime }=0\mathrm{}$ and $v^{\prime }>~3$. The relative populations of the $v^{\prime }=0\mathrm{}$ to $v^{\prime }>~3$ levels are strongly dependent on the excited rotational level of the $C$ state. These data are consistent with known perturbations between the nearly degenerate $C{}_{}{}^2{}_{}{}^{}\Pi$, $v^{\prime \prime }=0\mathrm{}$ Rydberg and $B{}_{}{}^2{}_{}{}^{}\Pi$, $v=7\mathrm{}$ valence levels.

Space-dependent extrema of the one-loop effective action in quantum field theory are found with use of scattering variables in the angular momentum. The $N$-component $g{\left({\overrightarrow{\varphi }}^2\right)}^2$ theory in three space dimensions is studied in detail. These instantons are classified in "homotopy classes" by "Regge poles." A comprehensive picture of them is obtained from exact results in the limits $g\to 0^{+}$ and $g\to \infty$ and from variational calculations. The large-order behavior of the $\frac{1}{N}$ series is obtained.