We suggest a method of using the average pair field of one superconductor to probe the fluctuation pair field of a second metal at temperature above the latter's superconducting transition point. The two metals should be fabricated as a strongly coupled tunnel junction and the dc $I-V$ characteristic measured as a function of both the bias voltage $V$ and the amplitude of a magnetic field $H$ parallel to the junction interface. The resultant $I-V$ characteristic is predicted to give a direct measurement of the frequency and wave-vector dependence of the $\Delta$ susceptibility characteristic of the superconducting transition.

The interaction between a moving dislocation and the electrons in a superconductor is treated theoretically. The results are in qualitative agreement with recent measurements of flow stress in superconductors.

Magnetic measurements of superconducting transitions of very pure isotopically separated bulk samples of Ga and Zn reveal a large "paraconductive" effect. This is contrary to the prediction for such systems by Aslamazov and Larkin based on corrections to first order in the fluctuations in the system. It is suggested that this discrepancy may be explained by increased electron pair lifetimes due to the absence of isotopic and other scattering of phonons allowing higher order processes to be significant.

Measurements of the anisotropic critical field $H_{c2\mathrm{}}$ of Nb at temperatures down to 0.06 K show that its temperature dependence contains a logarithmic factor as predicted by Gor'kov on the basis of a nonlocal theory for an isotropic type-II superconductor. The critical field extrapolated to zero temperature, when averaged over all crystallographic directions and normalized to the slope of the critical field for $T\approx T_c$, has an enhancement close to that predicted by the Hohenberg-Werthamer calculation for the nonlocal effects of Fermi-surface anisotropy, as evaluated by Mattheiss for a band model of niobium.

The room-temperature electrical resistivity of EuO is reported as a function of pressure up to 10 kbar. For the higher resistivity samples the pressure coefficient corresponds very closely to the observed shift of the optical absorption edge with pressure. Both the temperature and pressure dependence of the electrical resistivity are explained in terms of a model in which electrons are distributed between a temperature- and pressure-sensitive conduction band and a localized stationary trap level.

The angular dependence of the external photoemission is calculated for a free-electron-like metal. Numerical examples are given for sodium. Electrons which leave the solid without scattering have a very anisotropic spatial distribution: The intensity $\frac{\mathrm{dI}}{d\Omega }$ has discontinuities caused by the sharpness of the Fermi surface. These distributions can be used to determine the band structure of the metal.

The parquet-diagram technique is used to include vertex corrections in a model of local moment formation self-consistently. A Curie-law susceptibility is found in an approximation valid at high temperatures.

From an essentially model-independent analysis of the ratio of cross sections for the reactions ${}_{}{}^7{}_{}{}^{}\mathrm{Li}(p, n_0){}_{}{}^7{}_{}{}^{}\mathrm{Be}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}(p, n_1){}_{}{}^7{}_{}{}^{}\mathrm{Be}\left(0.43\mathrm{} \mathrm{MeV}\right)$, and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p, n_0){}_{}{}^6{}_{}{}^{}\mathrm{Be}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$, it is concluded that $\frac{V_{\sigma \tau }}{V_{\tau }}=0.66\mathrm{}\pm 0.08$ and is independent of bombarding energy from 10-20 MeV.

The asymmetry $A=\frac{(d{\sigma }_{\perp }-d{\sigma }_{\parallel })}{(d{\sigma }_{\perp }+d{\sigma }_{\parallel })}$ of the differential cross section for the reaction $\gamma d\to {\pi }^{-}\mathrm{pp}$ has been studied with linearly polarized photons of 3.0 GeV at squared four-momentum-transfers between 0.15 and 2.0 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The asymmetry was found to be positive at $-t$ values below 0.3 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, dipping to negative values between 0.4 and 0.6 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, and then rising again to positive values above 0.7 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$.

We present a heuristic argument suggesting that at high energies the effect of multiple scattering off the energy shell becomes important for an understanding of the propagation of one elementary particle through another.

We report the observation of a new four-pion resonance $\rho \mathrm{}\left(1630\right)\mathrm{}$ with mass 1632±23 MeV and width ${110}_{-30\mathrm{}}^{+40\mathrm{}}$ MeV produced in the channel $K^{+}p\to K^0{\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^{0}p$ and decaying predominantly to ${\rho }^{0,-}{\pi }^{0,+}{\pi }^{+}$ and $\omega {\pi }^{+}$. No decay is observed into ${\pi }^{+}{\pi }^0$, $K^{+}{\overline{K}}^0$, ${\rho }^{+}{\rho }^0$, or $A_2\pi$, so that association with the $g$ is precluded and the spin and parity probably lie in the unnatural series. The $\rho \mathrm{}\left(1630\right)\mathrm{}$ is associated with a $K\rho \mathrm{}\left(1630\right)\mathrm{}$ enhancement near threshold. This and other production characteristics are consistent with a double Regge pole exchange mechanism.

The branching ratio for the process $K^{+}\to {\pi }^{+}+\nu +\overline{\nu }$ is shown by a counter spark chamber experiment to be less than 1.2×${10}^{-6\mathrm{}}$ of all decay modes, assuming a pion energy spectrum like that of $K^{+}\to {\pi }^0+e^{+}+\nu$. Our apparatus was sensitive to pions in the kinetic energy range 117-127 MeV.

The suppression of drift instability is observed by applying a homogeneous rf electric field in a dc discharge diffused plasma. The instability amplitude is reduced by more than a factor of 30 and, concomitantly, a decrease of plasma loss across the magnetic field is also observed.

We have measured the critical magnetic field $H_c$ of aluminum films, 50-220 Å thick, at temperatures between 0.4°K and the transition temperature. For the thinnest films a qualitative change in the form of the transition for $\frac{T}{T_c}<0.5\mathrm{}$ indicates the presence of the first-order phase transition predicted for paramagnetically limited superconductors. The results also seem to demonstrate the existence of fluctuation broadening at higher temperatures.

Low-temperature measurements of the absorptivity of superconducting and normal Pb in the phonon frequency region 15-200 ${\mathrm{cm}}^{-1\mathrm{}}$ show an onset of absorption when the photon energy is large enough to excite appreciable numbers of acoustic phonons. The onset begins aroung the transverse phonon frequency $\Omega \simeq 35$ ${\mathrm{cm}}^{-1\mathrm{}}$ in the normal metal and around $\Omega +2\mathrm{}\Delta \simeq 55$ ${\mathrm{cm}}^{-1\mathrm{}}$ in the superconductor. Most features of the data can be explained by a "Golden Rule" calculation of the phonon-generation process proposed by Holstein.

We report results of studies utilizing ultraviolet synchrotron radiation as a selective excitation source for the $R$-line fluorescence transitions of ${\mathrm{Cr}}^{3+}$ in cubic MgO and ${\mathrm{Al}}_2$${\mathrm{O}}_3$. Pump bands for these fluorescences spanning the near and vacuum ultraviolet are identifiable as charge transfer bands of the Cr${\mathrm{O}}_6^{3-}$ complex. We report the observation of broad bands originating from ligand-to-metal bands and terminating in ${\mathrm{}\left(3d\right)\mathrm{}}^3$ states. Comparison of the excitation spectra of the broad-band fluorescence with that of the $R$ lines allows us to assign certain properties to the charge-transfer bands.

The $f$-sum rule is applied to the conduction- and valence-band edges at the $L$ point in PbS, PbSe, and PbTe. Experimental values of the energy gaps and electron and hole effective masses for PbS and PbSe follow the $f$-sum rule while those for PbTe do not. It is proposed that the well-known anomaly in the relative values of the energy gap of these semiconductors is due to an irregular value for PbTe.

Small-angle optical harmonic scattering in N${\mathrm{H}}_4$Cl reveals the presence of long-range, macroscopic order well above the transition temperature, $T_{\lambda }=242.6\mathrm{}°$K, for orientational disordering of the N${\mathrm{H}}_4^{+}$ ions.

Domain-wall mobility values from 6000 cm ${\sec }^{-1\mathrm{}}$ ${\mathrm{Oe}}^{-1\mathrm{}}$ at 300°K to 50 000 cm ${\sec }^{-1\mathrm{}}$ ${\mathrm{Oe}}^{-1\mathrm{}}$ at 77°K, among the highest observed in insulating magnetic materials, have been measured in YFe${\mathrm{O}}_3$. We have observed a monotonic temperature dependence of mobility which is qualitatively different from that found in other magnetic insulators and which we believe represents intrinsic behavior of wall mobility in YFe${\mathrm{O}}_3$. Domination of wall relaxation by surface roughness has been eliminated by proper surface preparation.

The perpendicular resonance linewidths of standing-spin-wave modes in Permalloy thin films have been measured as a function of temperature from 4 to 300°K. It is found that the linewidths obey the relation $\Delta H_k\mathrm{}\left(T\right)=\Delta H_k\mathrm{}\left(0\right)(1-a_k{T}^{\frac{3}{2}})$ where $\Delta H_k\mathrm{}\left(0\right)\mathrm{}$ is the linewidth at absolute zero of the spin-wave mode indexed by $k$. The ratio $\frac{a_k}{c}$ is found to decrease regularly as the mode number increases; $c$ is the Bloch constant (describing the temperature dependence of the magnetization).