A spin and parity decomposition is presented of the (${\pi }^{+}{\pi }^{+}{\pi }^{-}$) final state formed opposite a proton by incident 13-GeV/c ${\pi }^{+}$ mesons. The $A_3$ enhancement is identified as the $2^{-}$ amplitude decaying to $f^0{\pi }^{+}$ via an $S$ wave. A change in relative phase is noted between the $2^{-}S$ amplitude and the other principal contributions; this is not incompatible with analyses of the ${\left(3\mathrm{}\pi \right)}^{-}$ system. The method employs the University of Illinois three-body partialwave analysis program.

All independent energy intervals have been measured in the metastable $1s2s2p{}_{}{}^4{}_{}{}^{}P$ state of the helium negative ions ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{-}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{-}{}_{}{}^{}$. These results are of sufficient precision to provide a critical test of any proposed wave functions for this state and, when adequate wave functions become available, can be used to test relativistic and radiative corrections in three-electron atomic systems.

Two techniques of laser photodetachment spectroscopy have been utilized to provide the first accurate experimental determinations of alkali-atom electron affinities. Strong resonances corresponding to autodetaching states are found near the first ${}_{}{}^2{}_{}{}^{}P$ levels of the neutral alkalis. These resonances are by far the narrowest observed to date in electron-atom systems.

Binding energies of the ground ${}_{}{}^1{}_{}{}^{}S$ states of the alkali negative ions are calculated using the coupled equations of scattering theory, based on semiempirical effective potentials for the neutral atoms. An additional true bound state with configuration ${}_{}{}^3{}_{}{}^{}P$ lying just below the first excited state of the neutral atom is predicted for every species except ${\mathrm{Li}}^{-}$.

We report a significantly shortened scattering lifetime in molecular iodine when the frequency of a single-mode 5145-ÅA incident laser is tuned away from resonance with a discrete transition. This observation of a shortened scattering time is indicative of what has been conventionally called a Raman process. Off-resonance lifetime measurements, as reported here, may provide a means of determining the relative contribution to the absorption linewidth of homogeneous and inhomogeneous broadening.

The dielectric function for the two-dimensional guiding-center plasma is discussed. An error is noted in a calculation based on the Vlasov equation by Lee and Liu and an improved derivation is given using the Kubo formalism. Although this new dielectric function embodies the correct screening effect, it does not (contrary to earlier suggestions) essentially change the Taylor-McNamara result for the diffusion coefficient.

Conditions of global energy and pressure balance are applied to a cylindrically symmetric plasma column having a $B_{\theta }$ confining field and a $B_z$ stabilizing field, as exist in stabilized $z$ pinches and tokamaks. In the process of producing stable configurations the plasma pressure due to Ohmic heating during magnetic field diffusion may become too large for the confining field to contain.

We show that collision-induced light scattering at the frequency range of vibrational Raman bands of perturbed molecules can be observed and analyzed and that for gases the scattering process is similar to the one of depolarized Rayleigh scattering. In particular the $I_{\mathrm{VH}}$ component of the totally symmetric ${\nu }_1$ vibration of S${\mathrm{F}}_6$ and C${\mathrm{F}}_4$ has been studied. The depolarized light scattering at the ${\nu }_1$ Raman band of liquid S${\mathrm{F}}_6$ is also discussed.

The existence of polarization modes formed by light coupling to pairs of elementary excitations in liquid helium is suggested on theoretical grounds. The mode coupling is calculated by considering the atomic polarization associated with density fluctuations of two quasiparticles with small total momentum. The mode interactions involve the induced dipole moment of helium atoms and can be enhanced by an external field. The polarization modes may be observable in Raman scattering experiments.

Measurements of the impedance of phase-biased superconducting point contacts are interpreted in terms of the Josephson expression for the total current, $i=i_{c}sin\varphi +G_0(1+\alpha \times cos\varphi )V$. The data give good agreement with this expression and yield a parametric inductance $\mathcal{L}\left(\varphi \right)=\frac{\hslash }{2e{i}_{c}cos\varphi }$ and a phase-dependent conductance $G\left(\varphi \right)=G_0(1+\alpha cos\varphi )$, with $\alpha \approx -1\mathrm{}$.

It is shown that attractive electron-electron interaction arising from the exchange of two optical phonons is a possible mechanism for superconductivity in some degenerate semiconductors. This mechanism is present independent of whether the semiconductor is many-valley or not. Application to SrTi${\mathrm{O}}_3$ is discussed.

We present experimental evidence for the interaction of vortex lines with a controlled pinning configuration induced by periodic thickness modulation of superconducting films. The critical current density as a function of a transverse magnetic field shows characteristic peaks at well-defined field values. These features give evidence for matching of the two-dimensional vortex-line lattice with the one-dimensional periodic pinning structure. A model is proposed which accounts for the observed temperature dependence of the matching effects.

We describe nuclear-orientation experiments on $\mathrm{La}\mathrm{Ce}$ alloys under pressure and show that, in an analysis with a minimum of parameters, dilute $\mathrm{La}\mathrm{Ce}$ can be described by an ionic model in the pressure range studied (0-10 kbar). Our results are compared to indirect magnetic data extracted from measurements of transport properties.

We report three fully self-consistent calculations of the ionization potential, charge density, and surface potential for the Si(111) surface in which the normal coordinates of the outer two planes of surface atoms were allowed to vary. The ionization potential, calculated to be 5.4 eV, and the Fermi energy (relative to the valence-band maximum), calculated to be 0.3 eV, are both relatively insensitive to surface geometry. This is not true of the surface-state bands, which are quite sensitive to surface geometry.

The oxidation of strontium has been studied by Auger-electron spectroscopy. It is found that the surface of Sr remains metallic during oxidation, in support of recent photoemission experiments. A model based on the large electrostatic or Madelung energy of "ionic" metal/adsorbate systems is suggested that explains the phenomena.

EPR measurements of ${\mathrm{Gd}}^{3+}$ impurities in PrAl${\mathrm{O}}_3$ show that the direction of maximum electric field gradient at the ${\mathrm{Pr}}^{3+}$ site rotates continuously from the [101] to [001] perovskite axis below 151 K. This angle gives a direct measure of the displacement associated with the optical phonon mode participating in the Jahn-Teller transition; the angle is found to vary as ${(T_c-T)}^{\frac{1}{2}}$ near $T_c$.

We present a dispersion-theoretic formalism for obtaining the off-shell $t$ matrix, which allows the possibility of working directly from relativistic meson theory, without the necessity of explicitly using a potential. The formalism is illustrated for two simple models of the two-nucleon interaction.

We report evidence for an excited $K^{\pi }=0^{+}$ rotational band in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ and its mixing with vibrational states. The mean life of the 937-keV $0^{+}$′ state was measured to be 22.8±1.4 nsec, yielding $B\left(E2\mathrm{}\right)=36\mathrm{}\pm 7$ single-particle units for the 75-keV $0^{+}$′ → $2^{+}$ transition. From in-beam, $\gamma$-ray spectroscopy following the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 2p)$, a strong $\gamma$-ray cascade was observed from an yrast band of levels $0^{+}$, $2^{+}$,... to spin ${12}^{+}$ in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$.

A variational expression is used to prove that all axisymmetric modes of the Kerr sequence of rotating black holes are stable.

The one-loop divergences of coupled general relativity and electrodynamics cannot be absorbed by renormalization.