Differential cross sections for the (${\pi }^{-}, n$) reactions in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ have been measured at energies of 100, 200, and 290 MeV. The angular distributions for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are different, with ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ characterized by an oscillatory pattern with a dip at a fixed angle of ≃ 70°. The forward-angle cross sections show a simple dependence upon momentum transfer for both ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. These results are discussed in the context of single-nucleon and multinucleon reaction diagrams.

With a zero-range interaction a valence spin-up neutron will not interact with core spin-up neutrons and hence will not deform them; it will deform spin-down neutrons. This introduces a spin-quadrupole correlation. An ideal operator for probing this correlation is the $M3\mathrm{}$ operator, since this operator is crudely $E2\mathrm{}\times M1\mathrm{}$. The suppression of the $M3\mathrm{}$ moment in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ due to this effect, as well as due to the spin dependence of the interaction, is considered.

We suggest that, within the framework of the interacting-boson model, the group O(6) of orthogonal transformations in six dimensions may be useful in classifying nuclear spectra at the end of major shells. We derive analytic expressions for the energy levels and electromagnetic transition rates in this limit.

New theoretical predictions for the contribution to elastic photon scattering from atoms due to the bound atomic electrons are compared with recent experiments and previous theory. At 1.33 MeV, we resolve the large-angle disagreement for experiments on lead. For 2.75-MeV photons scattered by lead, we confirm the theoretical Rayleigh scattering amplitudes of Cornille and Chapdelaine. At 6.84 MeV, we estimate that the form-factor approximation yielded predictions for the $L$-shell Rayleigh amplitudes which were too large by 15%. For experiments below 100 keV, the form-factor approximation is poor.

Enhanced noble-gas NMR signals are observed in mixed noble-gas-rubidium samples by monitoring spin polarization of the optically pumped rubidium ensemble mechanized as a magnetometer. These signals are believed to arise through electron exchange enhancement of the contact hyperfine interaction during noble-gas-rubidium binary collisions. Polarization of the noble-gas magnetization is obtained through spin exchange with the rubidium ensemble.

It is found that the nonlinear wave-particle interaction based on the single-wave model can be changed strongly by introducing effects of weak collisions into plasma electrons. These collisions are too weak to change the linear stage. However, they alter the phase relation between the single wave and the trapped electrons in the nonlinear stage. As a result, the wave amplitude of the first minimum decreases anomalously and the persistent trapped-particle oscillations in the collisionless case are destroyed.

A procedure which reconciles long parallel wavelength, characteristic of plasma instabilities, with periodicity in a sheared toroidal magnetic field is described. Applied to the problem of high-$n$ ballooning modes in tokamaks it makes possible a full minimization of the potential energy functional $\delta W$ and shows that previous calculations overestimated stability.

We describe a new technique to measure the spatial distribution of plasma density fluctuations integrated over both frequency and wave vector. Measurements are reported of the frequencies, wave vectors, amplitudes, and also the spatial distributions of low-frequency density fluctuations present in the alcator tokamak. Two regimes can be identified. In high-density plasmas ($\overline{n}>{10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$) the fluctuations are peaked at the limiter radius with a fluctuation amplitude of $\frac{\tilde{n}}{n}\simeq 1$. At lower densities the fluctuation amplitudes peak in the interior of the plasma with $\frac{\tilde{n}}{n}\simeq 0.07\pm 0.03$.

An ${\mathrm{O}}_2$ adsorption state on the Si(111) 2×1 surface has been found which will remove surface states without producing a chemical shift of the Si $2p$ core level, suggesting a strongly covalent bond. This is accomplished by using an initial exposure pressure of ${10}^{-8\mathrm{}}$ Torr. Exposures using an initial exposure pressure of ${10}^{-6\mathrm{}}$ Torr also remove the surface states but produce a 2.0 eV Si $2p$ chemical shift indicating an ionic bond different from that of Si${\mathrm{O}}_2$ (shift of 3.8 eV).

We report experimental evidence showing that the electric-field-dependent yield of carriers excited in the track of an $\alpha$ particle stopping in liquid argon is dominated by geminate (initial) recombination of electron-ion pairs. This is the first confirmation of geminate carrier recombination in a noble-gas liquid. The thermalization length of the hot electrons is determined to be about 28 nm.

uv photoemission results using filtered $h\nu =40.8\mathrm{}$-eV radiation show strong shifts in the low-lying $\mathrm{C}\mathrm{}\left(2s\right)\mathrm{}$-derived levels of chemisorbed hydrocarbons on Ni relative to the higher-lying $\sigma$ levels. These differential shifts provide evidence for initial-state potential and/or rehybridization effects which are important in interpreting high-lying valence orbital shifts and the bonding of chemisorbed species.

Fourier analysis applied to the recently introduced thermal pulse method yields new and unique relations between the time-dependent pyroelectric response of a thin specimen and the Fourier coefficients of the charge or polarization distribution across its thickness. The new analysis is applied illustratively to thermal pulse data for a vinylidene fluoride copolymer electret.

A scaling theory is used to show that for temperatures $T\ll U$, the properties of the asymmetric Anderson model ($U\gg \left|E_d\right|, \Delta$) are universal functions of the scaling invariants $\Delta$ and ${E_d}^{*}=E_d+\left(\frac{\Delta }{\pi }\right)\ln \left(\frac{W_0}{\Delta }\right)$, where $W_0$ is the conduction electron bandwidth or $U$, whichever is smaller. Crossovers between various regimes of simple behavior as the temperature changes are described. $\left|{E_d}^{*}\right|\lesssim \Delta$ is identified as the criterion for a "mixed-valence" ground state, where the susceptibility $\approx {\Delta }^{-1\mathrm{}}$. For $-{E_d}^{*}\gg \Delta$, there is a local-moment regime with a Kondo temperature $T_{\mathrm{K}}\approx \Delta \exp \left(\frac{\pi {E_d}^{*}}{2\Delta }\right)$.

I examine the new gauge theory of gravitation theory proposed recently by Mansouri and Chang. It appears that the predictions of the theory are indistinguishable from those of general relativity with regard to the usual tests. With the aid of the symbolic manipulation computer system, macsyma, I find that the theory possesses a remarkable similarity to Einstein's theory with respect to vacuum solutions. While the field equations are greatly different, a question arises whether there are any solutions of the new equations which are not Einstein vacuum spaces.

The differential cross sections for $\gamma p\to \gamma p$ and $\gamma p\to {\pi }^{0}p$ have been measured from $\mathrm{}\left|t\right|=0.7\mathrm{} \mathrm{to} 4.3$ Ge${\mathrm{V}}^2$ and for incident energies in the range 2 to 6 GeV. The energy dependence of Compton scattering is well described by parton model ideas. However, the energy dependences of ${\pi }^0$ photoproduction and the ratio of Compton scattering to ${\pi }^0$ photoproduction are not consistent with dimensional counting arguments.

We have observed anomalous electron production in multiprong events produced by $e^{+}{e}^{-}$ annihilation at the $\psi \mathrm{}\left(3772\right)\mathrm{}$. For electron momenta greater than 300 MeV/c we measure an anomalous electron production cross section of 1.1 ± 0.3 nb. The measured spectrum is consistent with that expected for semileptonic $D$ decay. With reasonable assumptions we find the branching ratio for $D$ decay to an electron plus additional particles, averaged over the neutral and charged $D$, to be (7.2±2.8)%.

We discuss the consequences of our classical meron-pair model on the quark-confinement phase transition in an SU(2) Yang-Mills quantum field theory.

The requirement that $P$ and $T$ be approximately conserved in the color gauge theory of strong interactions without arbitrary adjustment of parameters is analyzed. Several possibilities are identified, including one which would give a remarkable new kind of very light, long-lived pseudoscalar boson.

In inclusive electroproduction, the production ratios of kaons to pions for both charge signs, and of $K^{+}$ to $K^{-}$, have been measured in the positive-$x_{\mathrm{F}}$ region. The $\frac{K}{\pi }$ data for a deuterium target display behavior similar to that for a hydrogen target. The $\frac{K^{+}}{{\pi }^{+}}$ ratio shows a general rise and the $\frac{K^{-}}{{\pi }^{-}}$ ratio shows a decrease as $x_{\mathrm{F}}$ increases. For high $x_{\mathrm{F}}$, $\frac{K^{+}}{{\pi }^{+}}$ increases with ${P_T}^2$ while $\frac{K^{-}}{{\pi }^{-}}$ stays flat. The $\frac{K^{+}}{K^{-}}$ ratio shows a dramatic rise as $x_{\mathrm{F}}$ increases.

We present additional evidence against the vector-meson hypothesis obtained from the $\mu -e$ events accumulated at SPEAR. Assuming that $\tau$ is a heavy lepton, we show that the data satisfy predicted scaling in the $z$ variable and determine the "Michel parameter" for the $\tau$ decay to be $0.32<\mathrm{}\rho <~1$.