With use of the technique of spin-polarized photoemission the magnetic properties of the chromium (100) surface have been investigated. Highly diluted oxygen incorporated into the lattice induces magnetic long-range order whereas oxygen adsorbed on top of the surface does not. No indication of ferromagnetism of the oxygen-free surface has been observed.

A new interpretation of the scalar product in Hilbert space was presented recently by Aharonov, Albert, and Au. Here the essential equivalence between such a view-point and Wigner's exact reformulation of nonrelativistic quantum mechanics using distribution functions is pointed out.

Two reactions, ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$+ ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{170}{}_{}{}^{}\mathrm{Er}$+ ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, have been used to produce ${}_{}{}^{200}{}_{}{}^{}\mathrm{Pb}$. Measurements of fission and evaporation residues allow the fission probability to be obtained as a function of input angular momentum. Fission sets a sharp limit ($\sim 35\hslash$) to the angular momentum which can be observed in the evaporation residues.

Discrete yrast transitions from states with spins up to $I=38\mathrm{}$ have been observed in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Er}$ via the reaction ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}({}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}, 4n\gamma )$. In addition to the pronounced backbend at $I=14\mathrm{}$ and the upbend at $I=28\mathrm{}$ previously known, the start of a third yrast discontinuity at $I=38\mathrm{}$ is indicated. Candidates for the $I=40\mathrm{}$ state are suggested and possible causes of the yrast discontinuity are discussed.

The Wannier theory for the double escape of two electrons from a positive ion is extended to general values of the total orbital and spin angular momentum and parity of the pair. Except for ${}_{}{}^3{}_{}{}^{}S_{}^e{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}P_{}^e{}_{}{}^{}$, all states are described by the same threshold law. Specific results on the correlations in energy, angle, and spin of the electrons are derived and compared with experimental data.

This paper describes observations of magnetohydrodynamic instability with neutralbeam heating in the ISX-$B$ tokamak and the theory specifically developed to support these experiments. The observed magnetohydrodynamic activity is explained by the resistive model presented but is not responsible for the observed degradation of confinement. Increasingly important $n>\mathrm{}1\mathrm{}$ pressure-driven modes are predicted by the theory for the higher experimental ${\beta }_p$ values, but there is no experimental verification of their presence.

The spontaneous formation of a finite-amplitude density wave of hcp lattice symmetry is discussed, following the work of Ramakrishnan and Yussouff. The freezing parameters do not depend on the interatomic force law, contain no adjustable parameters, and can be improved perturbatively. The results agree very well with those from computer simulation for a wide range of systems.

Energy losses observed when low-energy electrons were scattered from a Cu(100) surface exposed at $T\sim 15$ K to ${\mathrm{H}}_2$ (and ${\mathrm{D}}_2$,HD) lie close to rotational and rotational-vibrational transitions (${\mathrm{H}}_2$,${\mathrm{D}}_2$) of the free molecules. Both $o$- and $p$-${\mathrm{H}}_2$ and -${\mathrm{D}}_2$ physisorb on the surface, with negligible conversion on the time scale of the experiment. The relative populations were different from those characteristic of the adsorbing gas, suggesting a $j$-dependent sticking coefficient.

The lifetimes of the C-H and C-D stretch vibrational modes of methoxide adsorbed on Cu(100) have been measured by infrared spectroscopy. It is shown that the damping of these vibrational states is caused by excitation of electron-hole pairs in a region very close to the vibrating molecule. It is argued that the electron-hole pairs are excited because a resonance around the Fermi level fills and empties during the vibration.

For a dynamically disordered continuum it is found that the exact quantum mechanical mean square displacement $〈x^2\mathrm{}\left(t\right)\mathrm{}〉\sim t^3$, for $t\to \infty$. A Gaussian white-noise spectrum is assumed for the random potential. The result differs qualitatively from the diffusive behavior well known for the one-band lattice Hamiltonian, and is understandable in terms of the momentum cutoff inherent in the lattice, simulating a "momentum bath."

Optically detected magnetic resonance in $a$-${\mathrm{As}}_2$${\mathrm{S}}_3$ has shown that the emission consists of a high-energy triplet exciton recombination overlapping a low-energy pair process. The results are consistent with recombination at axial defects such as ($D^{+}, D^{-}$) intimate valence-alternation pairs.

The valence of an atom occupying a particular crystal lattice site can be determined from the chemical shift in a transmission electron energy-loss spectrum obtained with the intensity of the incident electron wave maximized at that site by dynamical electron diffraction. The new technique is demonstrated by determining the location of ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions in a mixed-valence spinel.

A laser-induced pressure-pulse method for measuring the charge distribution in (10 to 100 μm thick) dielectric samples with a resolution of about 4 μ m is described. A short (< ns) energetic light pulse from a neodymium-doped yttrium aluminum garnet laser is applied to a specially coated surface of the sample. The recoil due to ablation of material from the coating generates a pressure pulse (∼2 ns) which propagates through the sample. The charge distribution is evaluated by measuring the electrode currents from 25- and 75-μm polymers charged with corona and electron-beam methods.

Analytic studies of the Yvon-Born-Green equation have suggested that it may show no true critical region for spatial dimension $d<~4$ but that for $d>\mathrm{}4\mathrm{}$ there is a critical point of the mean-field type. Presented here are the results of numerical solution of the equation which strongly support these suggestions. Thus the Yvon-Born-Green equation exhibits the correct borderline dimensionality of four and the expected mean-field behavior for $d>~4$, but for $d<\mathrm{}4\mathrm{}$ has only a region of long, but finite, ranged correlations.

Implementation of universality "reduces" the most general simple gauge group that treats all fermions of one color irreducibly to the gauge group $G=\mathrm{U}\mathrm{}\left(1\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\otimes \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}^{\prime }$. For the natural choice of Higgs representation, the $G$ gauge theory is the same, at low energy, as the standard U(1) ⊗ SU(2) theory. The fundamental representation of the unifying group breaks up into identical families of SU(2) doublets.

The small-angle correlation function of two indistinguishable particles produced in hadronic processes is shown in general to be unrestricted by Bose-Einstein or Fermi-Dirac statistics. The analogy of hadron interferometry to Hanbury-Brown and Twiss intensity interferometry can break down because of dynamical correlations between observed and unobserved fragments. Two physical examples in the context of relativistic nuclear collisions illustrate this point.

Evidence for a new resonance $\theta \to \eta \eta$ in the process $\frac{J}{\psi }\to \gamma \eta \eta$ is presented. The resonance parameters of the $\theta$ are $M=1640\mathrm{}\pm 50$ MeV and $\Gamma ={220}_{-70\mathrm{}}^{+100\mathrm{}}$ MeV. $J^{\mathrm{PC}}=2^{++}$ is preferred over $0^{++}$.

The discrepancy between the theoretical and the experimental values of the forward deuteron photodisintegration cross section is found to be sensibly reduced by the inclusion of the relativistic corrections (Darwin-Foldy and spin-orbit terms) in the charge density. On the contrary, the pionic corrections calculated in the pseudoscalar $\pi \mathrm{NN}$ coupling are in the opposite direction.

The nuclear gyromagnetic ratio of the 3291-keV $J^{\pi }={\frac{25}{2}}^{+}$ ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ level has been measured with use of $\gamma$-ray perturbed angular distribution techniques with the result $g=0.544\mathrm{}\pm 0.008$. The state was populated with the reaction ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}(t, 2n){}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$. With use of the known quantities $g({}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}{7}^{-}; E_x=2200\mathrm{} \mathrm{keV})$ and $g({}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}{\frac{9}{2}}^{+}; E_x=0\mathrm{} \mathrm{keV})$ the proton orbital magnetic $g$ factor for the $1h$ orbital was deduced to be $g_l=1.115\mathrm{}\pm 0.02$. This result has been corrected for wave-function admixtures and core polarization effects.

An isovector $M6\mathrm{}$ transition is observed for the first time in a ($p, n$) reaction. A prominent peak was seen at $E_x=5.545\mathrm{}\pm 0.025$ MeV in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ in the study of the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(p, n){}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ at $E_p=35\mathrm{}$ MeV. This state is interpreted as the "stretched" particle-hole state with $J^{\pi }=6^{-}$, $T=1\mathrm{}$, which corresponds to the 15.13-MeV state in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. Distorted-wave Born approximation analysis gives a result consistent with those for ($p, p^{\prime }$) and ($e, e^{\prime }$) reactions, indicating that at least 50% of the isovector $M6\mathrm{}$ strength is missing.