The relative importance of the different laboratory distances of interaction of highly virtual photons is discussed in terms of the data on inelastic $\mathrm{ep}$ scattering in the scaling region. The definition of a characteristic distance distinguishing between short-range and long-range interactions is given. The magnitude of this quantity is extracted from the data to be about 0.65 F.

The projected propagator of the dual-resonance model is presented. It is used to give an operator proof of duality and to construct various tree and loop operators.

In the context of the Chew-Snider version of the Amati-Bertocchi-Fubini-Stanghellini-Tonin pion-exchange model, we investigate certain multiperipheral mechanisms that could account for those phenomena that have hitherto motivated the two-fireball model. These mechanisms are (1) double diffractive dissociation, (2) the presence of a sequence of neutral particles on the multiperipheral chain, and (3) statistical fluctuations in the $\mathrm{logtan}\theta$ spectrum. At cosmic-ray energies they are of equal importance.

We present an $S$-matrix calculation of the $K_{l3\mathrm{}}$ form factors which can explain the parameter $\xi \simeq -1\mathrm{}$ of the more recent polarization measurements. Existence of a zero in the scalar form factor near the $K_{l3\mathrm{}}$ physical region and below the $K\pi$ threshold plays an important role. We show further that the theoretical arguments based on the soft-meson theorems are inadequate to predict such a zero in the scalar form factor irrespective of the symmetry-breaking patterns employed. Implications of the zero to the off-mass-shell extrapolation of the form factors are briefly discussed.

The ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ ground state of thallium has been optically pumped in the presence of various buffer gases. The measured cross sections for the destruction of the electron polarization are small (${10}^{-19\mathrm{}}$ to ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$), verifying the selection rule $M_J\nrightarrow -M_J$ for the adiabatic contributions and demonstrating the strong dependence of the nonadiabatic contributions upon the multiplet energy separation.

In a photoionization experiment involving polarized alkali atoms and circularly polarized photons we measured the strength of the spin-orbit perturbation in potassium, rubidium, and cesium. Our results are pertinent to the theory of photoionization and to the production of polarized electrons. Extrapolation of the results to photon energies below the ionization threshold provides access to the anomalous doublet line-strength ratio of discrete $P$ states.

A high-resolution measurement of the differential elastic-scattering cross section for the Ne-Ne system shows wide-angle oscillations consistent with the prediction for identical particles based on a Lennard-Jones (12, 6) potential derived from transport properties.

This note shows that the effect observed in the Schwarz-Hora experiment, in which an electron beam passing through a crystal irradiated with laser light proceeds to a nonfluorescent screen and radiates light the same color as the laser, is probably caused by electron bunching. The crystal provides a sharply defined region of electric field amplitude which makes bunching possible.

The attenuation of first sound near the lambda point can be interpreted as being due to two phenomena: (1) a relaxation process described by Pokrovskii and Khalatnikov occurring only below the lambda point, and having a relaxation time of $\frac{\xi }{C_2}$ where $C_2$ is the velocity of second sound and $\xi$ is a coherence length of magnitude $1.36\times {10}^{-8\mathrm{}}{(T_{\lambda }-T)}^{\frac{-2\mathrm{}}{3}}$ cm; (2) a critical attenuation which is nonsingular and symmetrical about $T_{\lambda }$.

We report two-dimensional numerical studies of the nonlinear evolution of the electrostatic instabilities of two interpenetrating ion beams in an electron background, and comparison with the predictions of linear and quasilinear theory.

Measurements of the lifetime for positron annihilation in metals show a temperature dependence which has been ascribed to the trapping of positrons at vacancies. An explanation of this trapping process is presented in terms of an effective potential well, whose depth is the difference between the bottom of the positron energy band in the solid and the potential felt by the positron inside the vacancy.

Evidence is given for the existence of a Kondo state in Ag:Mn with $T_{\mathrm{K}}\sim 40$ mK. The results suggest a field dependence of the local-moment relaxation time. The relation between the $\gamma$ anisotropy and $S_z$ is discussed.

A new modulation technique is described which enhances the structure in the spectral reflectivity of metals and alloys. This technique allows the determination of the critical energy for optical interband transitions. The method is applied to various $\alpha$-brass specimens containing between 0.5 and 10 at.% Zn. The threshold energy for interband transitions in these alloys varied between 2.15 and 2.27 eV. The results are compared with those of previous workers obtained by conventional reflectivity measurements.

Self-heating in films of amorphous silicon prior to switching results from application of voltage pulses producing lateral currents. A smooth, rapid, and highly localized temperature rise always precedes the switching event resulting in a filamentary formation bridging the gap. The negative electrode edge is hotter than the positive electrode edge, and the measured filament temperatures compare favorably with temperatures calculated assuming intrinsic conduction takes place in the confined dimensions of the filament channel.

A model for paramagnetic Ni-Cu alloys is proposed, wherein magnetic clusters with giant moment (∼ 10${\mathrm{\mu }}_{\mathrm{B}}$) interact via the itinerant electrons. The interaction is shown to oscillate in space with a wavelength of the order of the cluster size. A Curie-Weiss susceptibility results in $\theta$ becoming negative (antiferromagnetic interaction) at low Ni concentration.

The ($p,t$) and ($p$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) reactions on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ targets have been studied using 43.8-MeV polarized protons. The observed cross sections and asymmetries for most states are well reproduced by distorted-wave Born-approximation calculations. However, of the five $L=2\mathrm{}$ ($S=0\mathrm{}$) transitions observed, two exhibit asymmetries which disagree markedly with the other three and with distorted-wave Born-approximation predictions. Thus asymmetries in two-nucleon-transfer reactions do not always appear to be simply characteristic of the transferred quantum numbers.

The ($p,t$) reaction has been studied with 17-MeV protons on targets of ${\mathrm{Th}}^{230}$, ${\mathrm{U}}^{234,236,238}$, and ${\mathrm{Pu}}^{242,244}$. The results indicate unexpectedly strong $l=0\mathrm{}$ transitions to states at about 900-keV excitation. Their cross sections are approximately 15% of the ground-state transitions; this percentage does not change appreciably with neutron number. This result, together with other available evidence, seems to suggest a simple and rather stable collective mode which has not yet emerged from any theoretical calculations.

By comparing energy spectra of protons from ($p,p^{\prime }$) reactions on various tin isotopes, a clean separation between direct-reaction and compound-nucleus contributions is made and the two processes are studied independently. The compound-nucleus results are in good agreement with predictions from the Gilbert-Cameron level densities. The direct-reaction angular distributions become quite isotropic for large $-Q$; the direct reaction cross section at 17 MeV is about one-third of the total reaction cross section.

The optimized polynomial expansions of $p-p$ amplitudes represented by a chosen set of five invariant amplitudes are given and the transformation matrix between them and the conventional partial waves is worked out. Through this matrix, we have re-examined the results of the elastic $p-p$ phase-shift analysis below 400 MeV done by the Livermore group and found very significant improvements.

We present a simple absorptive optical model for all scattering angles. For simplicity, we discuss the case of pion-nucleon charge-exchange scattering and show how the model contains in a unified way the dip structures in both forward and backward directions. For comparison with experiment, we present a fit to elastic ${\pi }^{+}p$ scattering at $3 \frac{\mathrm{GeV}}{c}$ where data are available at all angles.