Photoelectric emission and work-function measurements on GaSb have shown that the surface potential, and therefore the band bending and work function, of freshly cleaved surfaces present variations of up to 0.5 eV over macroscopic distances along the surface. These properties vary over a period of several days at room temperature in the sense that band bending increases and inhomogeneities disappear, suggesting annealing of cleavage-induced strains or defects. The electron affinity and ionization energy of freshlyy cleaved surfaces are well defined: They do not present spatial or temporal variation. Related observations were made on InP and GaAs.

We measured the energy distribution of electrons emitted from a copper single crystal at 60° to the surface normal, using plane polarized light at normal incidence in the near uv region. Rotating the plane of polarization produced changes in the electron distribution between 5 and 28%. No such changes could be detected upon substituting a polycrystalline sample. The energy distribution of the single crystal differs considerably from that of the polycrystal. The results imply direct, $\overrightarrow{\mathrm{k}}$-conserving transitions and no scattering for a large fraction of those excited electrons which leave the crystal.

The critical magnetic neutron scattering from CoO has been measured near the Néel temperature $T_{\mathrm{N}}$. The diffuse intensity at various wave vectors was assumed proportional to $A_{+}{\left|\frac{T}{T_{\mathrm{N}}-1\mathrm{}}\right|}^{-\gamma }$ above $T_{\mathrm{N}}$ and $A_{-}{\left|\frac{T}{T_N-1\mathrm{}}\right|}^{{-\gamma }^{\prime }}$ below $T_{\mathrm{N}}$. Using the method of Als-Nielsen, we measured the temperature dependence of the critical scattering at several values of $q$ [the displacement from the (111) position in reciprocal space] and used these data to calculate the relative magnitudes of $\gamma$ and ${\gamma }^{\prime }$. In order to satisfy scaling law requirements we referred our measurements to a rigid lattice by correcting for the large tetragonal contraction below $T_{\mathrm{N}}$. We found that ${\gamma }^{\prime }=(1.02\mathrm{}\pm 0.02)\gamma$, and this suggests that static scaling laws may apply to CoO. In addition we ascertained that $\frac{A_{+}}{A_{-}}\cong 7.6\pm 1.5$ in agreement with the linear theory of Schofield, where $\frac{A_{+}}{A_{-}}=6.0\mathrm{}\pm 0.8$ for CoO.

Measurements of the tetragonal elongation in a CoO single crystal in the critical region above the Néel temperature $T_{\mathrm{N}}$ indicate that $\left|\frac{\Delta L}{L}\right|\propto {\left(\frac{T}{T_{\mathrm{N}}-1\mathrm{}}\right)}^x$, and below $T_{\mathrm{N}}$ that $\left|\frac{\Delta L}{L}\right|\propto {\left(\frac{1-T}{T_{\mathrm{N}}}\right)}^{x^{\prime }}$, where $x=0.67\mathrm{}\pm 0.10$ above $T_{\mathrm{N}}$ and $x^{\prime }=0.60\mathrm{}\pm 0.08$ below $T_{\mathrm{N}}$. We compare these critical exponents with two theoretical predictions of strain behavior in the critical region and find agreement in both instances.

Data analysis for nickel and gadolinium indicates the simple linear-model approximation for the parametric magnetic equation of state represents these data satisfactorily in the critical region. The results for nickel are in quantitative agreement with specific-heat data in the presence of magnetic fields.

Differential cross sections have been measured for the excitation, by 22.95-MeV protons, of states (up to and including the $6^{+}$ at some angles) in the ground-state rotational bands of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. Coupled-channel analyses of the angular distributions allow determination of the equilibrium deformation parameters ${\beta }_4$. The values ${\beta }_4={0.017}_{-0.030\mathrm{}}^{+0.015\mathrm{}}$ for ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ and ${\beta }_4=0.050\mathrm{}\pm 0.015$ for ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ do not agree well with theoretical predictions by Möller et al.

A method of search for an $\overline{N}N$ bound state is pointed out and evidence is presented for the existence of a $\overline{p}n$ bound state. It is produced in $\overline{p}d$ annihilations at rest and has been observed decaying into four and six pions. The binding energy is 83.3 ± 1.4 MeV and the width ≤8 MeV at the 95% confidence level.

A study of the ${A_2}^{+}$ mass spectrum in ${\pi }^{+}p$ interactions at $3.7 \frac{\mathrm{GeV}}{c}$ is presented. For a cut of $t^{\prime }=0.1\mathrm{}-2.0$ Ge${\mathrm{V}}^2$ and on eliminating the ${\Delta }^{++}$ we find that the three-pion mass spectrum in the ${A_2}^{+}$ region is fitted by the dipole formula with a confidence level of 53% and a single Breit-Wigner formula with a confidence level of 11%. Our result thus favors ${A_2}^{+}$ splitting although a single Breit-Wigner fit cannot be ruled out. We also report the ${A_2}^{+}$ decay branching fractions measured over all $t^{\prime }$ values. They are 0.78 ± 0.05, 0.15 ± 0.04, 0.06 ± 0.03, and < 0.02 for $\rho \pi$, $\eta \pi$, $K\overline{K}$, and ${\eta }^{\prime }\pi$, respectively, in good agreement with other experiments.

The differential cross sections for ${\pi }^{-}p$ charge exchange at 180° are given as a function of ${\pi }^{-}$ momentum from 1.8 to $6.0 \frac{\mathrm{GeV}}{c}$. Below $4 \frac{\mathrm{GeV}}{c}$ there is a resonancelike structure. Above $4 \frac{\mathrm{GeV}}{c}$ the data are in excellent agreement with a smooth exponential drop. A modification of the Igi model gives a good fit to the data. The momentum dependence of the moduli of the isospin-½ and $\frac{3}{2}$ amplitudes and their relative phase is presented.

The final states $K^{-}{\pi }^{+}n$ and ${\overline{K}}^0{\pi }^{-}p$ were measured in a $K^{-}p$ experiment at $5.5 \frac{\mathrm{GeV}}{c}$. The data on the angular distribution of the outgoing $K$ meson in the $K\pi$ rest system at low momentum transfer were analyzed by a simple model including $I=\frac{3}{2}$ $s$-wave and $I=\frac{1}{2}$ $s$-, $p$-, and $d$-wave amplitudes. The results show that the phase shift for the $I=\frac{3}{2}$ $s$ wave is negative. The two solutions obtained for the $I=\frac{1}{2}$ $s$-wave off-mass-shell phase shift are consistent with an $s$-wave resonance at either ∼0.85 or ∼1.2 GeV.

We observe a splitting in the $K^{+}{\pi }^{+}{\pi }^{-}$ mass spectrum in $K^{+}d$ interactions at $9 \frac{\mathrm{GeV}}{c}$. We find a mass of $1243\pm 8 \frac{\mathrm{MeV}}{c^2}$ and a width of ${70}_{-18\mathrm{}}^{+26\mathrm{}}$ for the lower mass state, and a mass of 1344 ± 8 and a width of less than $60 \frac{\mathrm{MeV}}{c^2}$ for the higher mass state. The isospin of both states is determined to be ½. The results can be interpreted as evidence for the mixing of two $J^P=1^{+} K^{*}$ states.

When particles like quarks and magnetic monopoles are produced in pairs, there is a suppression of the production due to the superstrong attractive forces which exist between the constituents of the pair. We present an approximate way of incorporating this effect into a production model, and estimate lower bounds on the masses of the particles from present experimental data using our method in conjunction with the standard statistical model.

A recent result of Aviv, Hari Dass, and Sawyer, relating the anomalous value of $\gamma \gamma \to \left(\mathrm{any}\mathrm{odd}\mathrm{number}\mathrm{of}\mathrm{pions}\right)$ to the anomalous rate of ${\pi }^0\to 2\gamma$, is demonstrated by conventional graph techniques. It is also shown that the neutral mode $\gamma \gamma \to n{\pi }^0$ is suppressed for all odd $n$.

We present a model for the Pomeranchukon which relates its couplings to those of the $f$ and $f^{\prime }$ trajectories. We successfully explain several features of total—cross-section data, and discuss $s$-channel helicity conservation at high energies in $\pi N$ scattering and $\rho$ photoproduction, but we do not expect it to be a feature of all diffractive processes.

In order to determine the differential cross section for excitation of a given radiative level, in ion-atom collisions, the scattered ions are detected at a given angle, in coincidence with the photons emitted by the excited target atoms. The method has been applied to the ${\mathrm{He}}^{+}$-He collision at laboratory energies of 200, 300, and 350 eV in the angular range 5-18 deg, for the $3{}_{}{}^3{}_{}{}^{}P$ level of He. At 200 and 300 eV, the differential cross sections exhibit an interference pattern which is characteristic of a curve crossing. The behavior is more complicated at 350 eV because, we believe, more than two molecular states are involved.

"Polarization-free" excitation cross sections for the $1{}_{}{}^1{}_{}{}^{}S-n{}_{}{}^1{}_{}{}^{}P$ transitions of He have been measured from threshold to 2 keV using a crossed-beam technique. Results have been made absolute using the accurately known oscillator strengths. Maxima in the cross sections for the $n{}_{}{}^1{}_{}{}^{}P$ levels occurred around 100 eV and were found to be 106×${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$ ($2{}_{}{}^1{}_{}{}^{}P$), 31×${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$ ($3{}_{}{}^1{}_{}{}^{}P$), and 13×${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$ ($4{}_{}{}^1{}_{}{}^{}P$).

We report observations of the ionization of atomic cesium by the simultaneous absorption of three ruby-laser quanta. Our results appear to be in qualitative agreement with theory, and indicate that circularly polarized ruby light produces ionization about twice as efficiently as does linearly polarized light.

The ${\mathrm{Ar}}^{+}$+Ar collision has been studied for evidence that an $L$-shell electron may be promoted to a higher bound level. An ion-ion coincidence apparatus was used on events where the incident energy $T_0$ was 25 keV and the scattering angle $\theta$ was 16°. We successfully sought those inner-shell vacancy-producing collisions in which no purely outer-shell autoionization processes took place and in which only one electron was ejected per vacancy. For such an event to occur the inner-shell electron must be promoted to a bound state. This effect can be accounted for using the promotion model of Fano and Lichten and provides additional evidence of the model's validity.

An experiment is described which determines the probability of nucleation of a quantized vortex ring by an ion as a function of the ion velocity. The "lifetime edge" produced by a series of such measurements is compared with the theoretical predictions of Donnelly and Roberts.

The temperature dependence of the vortex-core parameter is determined by means of precise measurements of vortex-ring velocities. The results agree with calculations based on the vortex-core model of Glaberson, Strayer, and Donnelly and disagree with the calculations of Pollock.