We present production and decay distributions for the reaction $\nu p\to {\mu }^{-}p{\pi }^{+}$ with $M_{{\pi }^{+}p}<1.4\mathrm{}$ GeV. This reaction is primarily $\nu p\to {\mu }^{-}{\Delta }^{++}$, but we find evidence for the presence of non-$\Delta$ amplitudes for $Q^2>1\mathrm{}$ Ge${\mathrm{V}}^2$. The data are fitted by various theoretical models. For $Q^2<1\mathrm{}$ Ge${\mathrm{V}}^2$ the best fit yields the value $M_A={1.25}_{-0.13\mathrm{}}^{+0.15\mathrm{}}$ GeV, using a dipole-nucleon axial-vector form factor in Adler's model, although none of these models successfully reproduces the observed $\Delta$-decay distributions.

Nonoverlapping orbitals make Hartree- Fock calculations possible in the presence of hard-core interactions. Such orbitals tend to be unfavorable to rotational invariance and to $\alpha$ clustering. They define a new type of collective motion, correlation vibration.

Antisymmetrization effects in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ heavy-ion potential and their dependence on the nucleon-nucleon interaction have been studied. It is shown that for some choices of nucleon-nucleon interaction the recently conjectured cancellation of antisymmetrization and polarization effects breaks down completely.

In a pion—$\gamma$-ray coincidence spectrum from 190-MeV ${\pi }^{-}$ reactions with ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, prominent lines are observed corresponding to the equivalent removal of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, $\alpha$, $t$, $d$, $p$, and $n$. When the data are normalized to $n$ removal and compared to the inclusive singles $\gamma$-ray data, pion-scattering cross sections on the order of (50-100)% of the total for these reactions are implied.

We have identified yrast states of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ to spin ∼37, with unusually strong population of high-spin states in the (${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, $4n\gamma$) reaction. Yrast isomers with spins ∼17, 21, 27, and 31 were detected. For $I>~14$ the yrast states scatter about a straight line on an $E$ vs $I(I+1\mathrm{})\mathrm{}$ plot, consistent with predictions for aligned-particle configurations. The slope of the line yields an effective moment of inertia 18% larger than the rigid-sphere value. This and other arguments suggest possible oblate deformation at high spin.

A theory of the branching ratio for radiative pion capture with respect to absorption of stopped negative pions is developed by analogy to the Primakoff theory for the total capture rate of ${\mu }^{-}$. It is shown that the systematics of pion absorption predict a linear dependence of the ratio of $\frac{\mathrm{}(A-Z)\mathrm{}}{2A}$. A comparison to experimental data tends to confirm this prediction.

Quasi-Landau resonances have been recorded for lithium atoms in magnetic fields of up to 47 kG, with a spacing of only half the cyclotron frequency rather than $\frac{3}{2}$ as expected from previous theory. The intensity distribution over satellites in the $l$-mixing region (including the appearance of parity-forbidden transitions) is discussed in terms of magnetic mixing among nearly degenerate levels. An intensity sum rule is demonstrated.

It is shown that at a high impact velocity $\overrightarrow{\mathrm{v}}$ the second-order Born term can provide a significant asymmetric (skew) contribution to the cusp at $\left|{\overrightarrow{\mathrm{v}}}_e\mathrm{}\right|=\left|\mathrm{}\overrightarrow{\mathrm{v}}\right|$ in the differential cross section for "electron capture to the continuum" from a hydrogenlike atom in its $1s$ state by a bare ion, where ${\overrightarrow{\mathrm{v}}}_e\approx \overrightarrow{\mathrm{v}}$ is the velocity of the emergent electron. The asymmetry in the cusp, heretofore unexplained, has been observed in several recent experiments.

A new Doppler-free stimulated-emission technique using an optically pumped laser with applications in spectroscopy and optical frequency standards is reported. An argon-laser-pumped cw ${\mathrm{I}}_2$ laser is used to demonstrate the technique as well as measure the complete hyperfine structure of the ${\mathrm{I}}_2$ $B{{\mathrm{O}}_{\mathrm{u}}}^{+}-X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}$ (43,83) $P\left(13\right)\mathrm{}$ line. Hyperfine coupling strengths obtained for the $X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}{v}^{\prime \prime }=83\mathrm{}$, $J^{\prime \prime }=13\mathrm{}$ level are $\mathrm{eQ}{q}^{\prime \prime }=-1550.1\mathrm{}\pm 0.5$ MHz and $C^{\prime \prime }=59\mathrm{}\pm 5$ kHz. In addition, the ${\mathrm{I}}_2$ laser has been actively stabilized to within 1 kHz of the observed line center of an ${\mathrm{I}}_2$ hyperfine component.

A modulated electron beam is injected into a low-$\beta$ plasma parallel to the confining field to investigate the energy-transfer rate from the electron beam to the plasma. Parametric excitation of electrostatic lower-hybrid waves and ion-cyclotron quasimodes is experimentally identified. The temperature of both ions and electrons is observed to increase significantly concomitant with the growth of the instability.

For density profiles, $N\left(y\right)\mathrm{}$, making a smooth transition from $N(-\infty )=0\mathrm{}$ to $N(+\infty )=\mathrm{const}$ with $\frac{d\ln N}{\mathrm{dy}}$ decreasing monotonically with $y$, it is shown that the Rayléigh-Taylor instability exhibits essentially different behavior above and below a certain critical wave number, $k_c$. For $k>\mathrm{}{k}_c$ the growth of the response to an initial perturbation is slower than exponential, $\sim t^{-\frac{1}{2}}\exp \left({\gamma }_{b}t\right)$. For $k<\mathrm{}{k}_c$ an unstable eigenmode (analogous to that in the sharp boundary case) exists, and purely exponential growth occurs.

Measurements of the dispersion curves on single crystals of Nb${\mathrm{D}}_{0.85}$ and Nb${\mathrm{H}}_{0.82}$ reveal two new excitations at $\hslash \omega =18.4\mathrm{} \mathrm{and} 10.8$ meV. The positions of these excitations are independent of temperature and mass of the light atom, but the linewidth is broader in the ${\alpha }^{\prime }$ solid-solution phase than in the $\beta$ phase, and broader in the hydrogen system than in the deuterium system.

Positive muons implanted in single-crystal Al doped with Mn are localized below 20 K in contrast to the case of pure Al, where the muon is completely delocalized down to 1 K. Applying the Anderson theory of localization, we show consistently that a coherent tunneling state, which exists in pure Al, is destroyed under the influence of lattice strains generated by the Mn impurities. Our data suggest strongly that the muons are localized at tetrahedral sites at 15 K.

Thermal conductivity measurements have been performed in nematic and smectic liquid crystalline phases by the forced Rayleigh light-scattering technique. Results show clearly that the thermal transport anisotropy is governed by the molecular shape anisotropy and by the molecular orientation but is independent of the smectic layer ordering.

The (110) surface atomic geometries of GaAs and ZnSe and of 2 × 1 reconstructed (111) surface of Si are calculated by minimizing the total energy of the electron-ion system. The corresponding reductions in total energy between the relaxed and unrelaxed surfaces are calculated to be - 0.51, - 0.30, and - 0.37 eV per surface atom, respectively. Subsurface relaxations are generally found to make a very small (≤ 0.02 eV) contribution to the reduction in total energy.

Angle-resolved photoemission offers a means for determining the presence and the wave vector of an incommensurate charge-density wave in a simple metal.

The instability which arises in current mean-field theories of spin-glasses is removed, within the replica method, by breaking the symmetry between replicas. For the Sherrington-Kirkpatrick (SK) model the spin-glass order parameter has the expansion $q=t+t^2+O\left(t^3\right)$ $(t=1-\frac{T}{T_c})$, which differs at $O\left(t^2\right)$ from that given by Sk.

Thin-film energy-band determinations of a surface-state-surface-resonance band in Al(001) are found to account completely for and clarify the new angle-resolved photoemission observations of Gartland and Slagsvold. The transition from a true surface state to a surface resonance is explained in terms of a mechanism in nearly-free-electron metals for the formation of surface resonances in "partial" Bragg-reflection bulk energy gaps.

Slow (<5 eV) positrons ($e^{+}$) are observed emanating from clean (submonolayer contaminated) single-crystal metal surfaces which are being bombarded by 0.1-3-keV $e^{+}$. A portion of the emitted slow $e^{+}$ from Al(100) has a narrow range of energies and a temperature-dependent intensity which suggests that these $e^{+}$ are thermalized in the bulk and have a negative work function ${\varphi }_{+}=-0.2\mathrm{}\pm 0.1$ eV. A higher-energy portion of the slow-$e^{+}$ spectrum has a temperature-independent intensity attributable to nonthermalized $e^{+}$.

We consider the magnetic-field ($H$) dependence of the magnetization ($M$) of a thin low-anisotropy ferromagnetic film near $T_c$ placed on a magnetically hard substrate well below its Curie temperature. Our mean-field-theory analysis uses a free-energy functional analogous to the ${\varphi }^4$ Lagrangian for a complex scalar field used recently in a description of solitons in charge-density-wave condensates. We find a novel critical point in the appropriate $M-H$ plane and comment on its accessibility to experimental investigation.