A comparison between the ${\pi }^{-}p$ scattering data and the predictions of the various phase-shift analyses is presented. In particular, it is pointed out that the dispersion relation fit of the CERN group fails to represent the data.

We have examined the scattering amplitude of two scalar particles in scalar electrodynamics for arbitrary order of perturbation, and found uncanceled terms proportional to $s{\left(\ln \mathrm{s}\right)}^n$, for $n$ any positive integer. This suggests a branch point or an essential singularity at $J=1\mathrm{}$, and that total cross sections vanish at infinite energy as some negative power of lns. This form fits very well the sum of the measured ${\pi }^{+}p$ and ${\pi }^{-}p$ cross sections between 8 and 22 BeV/c.

Field-theoretic model calculations for inelastic electron scattering show that (1) scaling laws must be weakly violated; (2) there is no evidence for $\frac{{\sigma }_T}{{\sigma }_S}=0\mathrm{} or \infty$; and (3) the angular spread in production amplitudes must increase as $\left|Q^2\right|$ increases and is roughly proportional to $\left|Q^2\right|$ for large $\left|Q^2\right|$, where $Q$ is the four-momentum of the virtual photon. Some experimental tests are suggested.

It is shown that an infinite set of daughter trajectories is required to saturate finite-energy sum rules consistently. In the presence of this infinite set, the sum rules by themselves do not constrain the energy dependence of the trajectory function.

Compound states of atoms are known to decay by the emission of a single electron into many states lying at lower energies. Compound states associated with doubly excited states lie at energies above the ionization potential, and therefore the decay into an ion by the emission of two electrons is energetically possible. This paper presents evidence for such a two-electron decay in the case of the $\left(2\mathrm{}{s}^{2}2p\right){}_{}{}^2{}_{}{}^{}P$ compound state of helium which derives from the $\left(2\mathrm{}{s}^2\right){}_{}{}^1{}_{}{}^{}S$ atomic state.

We have measured the $2{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-2{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ separation, $\Delta E_{\mathrm{H}}-{\mathcal{S}}_{\mathrm{H}}$, in atomic hydrogen by an atomic-beam rf method. We find $\Delta E_{\mathrm{H}}-{\mathcal{S}}_{\mathrm{H}}=9911.213\mathrm{}\pm 0.058$ MHz. The quoted error is 1 average deviation from the mean for 115 line centers.

The magnetohydrodynamic equilibrium and stability of the plasma-current multipole configuration have been demonstrated experimentally.

Measurements of the positive-ion mobility in He II are reported, and are analyzed in terms of scattering by elementary excitations.

The specific heat of liquid ${\mathrm{He}}^3$/${\mathrm{He}}^4$ mixtures has been measured at saturated vapor pressure for three values of the ${\mathrm{He}}^3$ mole fraction $x$ near the junction of the lambda and phase-separation curves. The specific heat at the lambda peak appears to be finite, continuous, and cusped. Both the lambda peak and the anomaly in the specific heat as the system goes from the two-liquid-phase region to the one-liquid-phase region tend to disappear as the junction of phase boundaries is approached.

A laser-produced plasma has been used in a new approach to the problem of investigating the mechanisms associated with the turbulent energy dissipation is a collisionless laboratory plasma. The measurements indicate that the two-stream instability enhances the resistivity in the wave front by more than two orders of magnitude and thus determines the width of the wave front to a value of about $d\approx \frac{13c}{{\omega }_{\mathrm{pe}}}$.

We have observed a temperature-dependent enhanced diamagnetism above the critical temperature in pure bulk indium which we attribute to the effects of thermal fluctuations. The magnitude of the effect and the manner in which it scales with magnetic field are in agreement with a finite-field generalization of a zero-field result based on the Ginzburg-Landau theory.

The excitation of a small ellipsoidal sample in an electromagnetic cavity is treated quantitatively as a two-wave Rayleigh-scattering problem. Application to the special case of a solid-state magnetoplasma shows that magnetoplasma resonance occurs when ${\kappa }^{\prime }=-\left(\frac{1}{L-1\mathrm{}}\right)$, with strength proportional to $\frac{1}{{\kappa }^{\prime \prime }}$, and approximate half-width ${\kappa }^{\prime \prime }$, where $\kappa ={\kappa }^{\prime }+i{\kappa }^{\prime \prime }$ is the net bulk dielectric constant of the material comprising the ellipsoid, and $L$ is the mks depolarization factor. New methods of deducing transport parameters from magnetoplasma resonance are outlined.

Measurements of the coefficient of linear thermal expansion accurate to 1% are reported for free-standing samples of solid argon for temperatures from 1 to 25 K. These data were obtained using a differential parallel-plate-capacitor technique and at low temperatures can be represented by $\alpha =(3.34\mathrm{}{T}^3+0.030\mathrm{}{T}^5)\times {10}^{-8\mathrm{}}$ ${\mathrm{K}}^{-1\mathrm{}}$ ($1<T<\mathrm{}6\mathrm{}$ K). When combined with other data, these results can be used to obtain Grüneisen parameters which are systematically 10% lower than those reported for anharmonic theories. Preliminary data also showed a low-temperature thermal expansion anomaly which is believed due to the spin-split ground state of ${\mathrm{O}}_2$ impurities.

An x-ray structural analysis on cerium under pressure was made in order to investigate its valence behavior in the metallic state. A new form, ${\alpha }^{\prime }-\mathrm{Ce}$, always fcc but strongly collapsed, was found to exist at pressures higher than 50 kbar. It was deduced that Ce is tetravalent in the ${\alpha }^{\prime }$ form. The atomic radius of ${\mathrm{Ce}}^{\mathrm{IV}}$ was calculated, and the probable values of the valency in $\gamma -\mathrm{Ce}$ and $\alpha -\mathrm{Ce}$ are also estimated.

The ${\mathrm{Nb}}^{93}$ spin-lattice relaxation time $T_1$ in the mixed state of niobium metal has been observed to depart at high temperatures from the temperature and field dependence predicted by the theory of gapless superconductivity. This anomaly indicates either a breakdown of the gapless theory or, more plausibly, the existence of a new relaxation mechanism at high temperatures.

We report the first observation of the radiative recombination from photoexcited hot carriers in GaAs. Our results show that the hot carriers have an effective temperature which implies a Maxwellian distribution. This temperature increases with the excitation intensity. An empirical relationship between this temperature and the power transferred from the hot carriers to the lattice is in quantitative agreement with the theoretical predictions for carrier scattering by polar optical modes.

On the assumption that in Ni-Cu alloys the spin moment on a Ni atom depends on the local atomic environment, it was possible to find moment values for the various atomic configurations so as to give average moments in reasonable quantitative agreement with the values measured in the ferromagnetic composition range. The local environment is specified by the number of Ni nearest neighbors and the number of Ni second-nearest neighbors. This model allows also a consistent qualitative interpretation of the effect on the average moment of low-temperature annealing treatment and of plastic deformation.

It is shown that it should be possible to reduce the dominant two-magnon linewidth well below the smallest value obtained to date by choosing the radius $R$ and thickness $S$ of a thin film of ferromagnetic insulator such that there are no modes degenerate with the main-resonance mode. For a sufficiently thin sample ($S\lesssim 1\mu$) the frequencies of the exchange modes are well above that of the main-resonance mode, and for a sufficiently small aspect ratio ($\frac{2R}{S}\lesssim 3\times {10}^3$) the low-order magnetostatic modes are also well resolved. In the limit of no two-magnon scattering, the resonance linewidth of yttrium iron garnet at 9.3 GHz approaches 0.2 Oe at 300°K, or a few mOe at 4.2°K.

A relationship is derived between the proton mean-square radius, the neutron mean-square radius, a pair correlation function in the nuclear ground state, and energy-weighted sums of the electric dipole photodisintegration cross sections to the two final isospin states.

We have studied isotopes of element 104 formed by bombarding ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ions. ${}_{}{}^{257}{}_{}{}^{}104$ and ${}_{}{}^{259}{}_{}{}^{}104$ were positively identified by milking their daughters, ${}_{}{}^{253}{}_{}{}^{}\mathrm{No}$ and ${}_{}{}^{255}{}_{}{}^{}\mathrm{No}$. ${}_{}{}^{257}{}_{}{}^{}104$ is a 4.5-sec alpha-particle activity with a complex spectrum; ${}_{}{}^{259}{}_{}{}^{}104$ is likewise an alpha emitter with a half-life of 3 sec. ${}_{}{}^{258}{}_{}{}^{}104$ is tentatively identified as an 11-msec spontaneous-fission activity.