An analysis was made of the decay angular distribution of rho mesons produced via $\gamma p\to p{\rho }^0$ by linearly polarized photons at 2.8 and 4.7 GeV. The reaction proceeds almost completely through natural-parity exchange, the contribution from unnatural-parity exchange for momentum transfers $\mathrm{}\left|t\right|<1\mathrm{}$ Ge${\mathrm{V}}^2$ being (3.1±2.2)% at 2.8 GeV and (-1.1±1.9)% at 4.7 GeV. The behavior of the density-matrix elements shows that the rho-production mechanism conserves $s$-channel c.m. system helicity for $\mathrm{}\left|t\right|<0.4\mathrm{}$ Ge${\mathrm{V}}^2$.

The angular distribution for the charge-exchange reaction ${\pi }^{-}p\to n{\pi }^0$ has been measured for an incident pion momentum of 6 GeV/c. The cross sections are presented for a range of crossed four-momentum transfer from $u=0.06\mathrm{}$ ${\mathrm{}\left(\mathrm{GeV}\right)\mathrm{}}^2$ (180°) to $u=-1.4\mathrm{}$ ${\mathrm{}\left(\mathrm{GeV}\right)\mathrm{}}^2$ (66° lab). These data are compared with the predictions of Barger and Cline and are found to be in qualitative but not quantitative agreement.

We conjecture that the linear polarization of a large-mass timelike photon emitted in high-energy hadron-hadron collisions is predominantly longitudinal ($\lambda =0\mathrm{}$). The conjecture can be tested experimentally by studying the decay angular distribution of muon pairs produced in $p\left(\pi \right)+N\to {\mu }^{+}+{\mu }^{-}+\mathrm{hadronic}\mathrm{system}.$

We have observed new effects in the Zeeman hyperfine spectra of ${\mathrm{H}}^1$ and ${\mathrm{Rb}}^{87}$ when a nonresonant linear radiofrequency field is applied perpendicular to the static field: The Zeeman lines coalesce in some cases; new sideband resonances also appear. A theoretical explanation is given for these effects. Some possible applications for atomic clocks and masers are considered.

The presence of strong rf electromagnetic echoes is reported in silver alloys containing small (≲0.1 at.%) amounts of Mn or Ni. The echoes are observable at 4 MHz from 1.8 to 300°K and possess an amplitude directly proportional to the applied magnetic field. The decay constant, $T_2$, is about 60 μsec and is not strongly dependent on impurity concentration or magnetic field. Echo amplitudes decrease with increasing impurity concentration.

Raman-shifted ruby-laser light on the high-frequency side of the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ resonance line (7665 Å) of potassium was self-focused by a dilute potassium gas.

We have measured the magnetic flux trapped in superconducting tin cylinders (56-μm i.d., 0.7- to 5-μm walls, 24 mm long) and find that for most values of applied magnetic field the entire cylinder is in the same quantized flux state trapping an integral multiple of $\frac{\mathrm{hc}}{2e}\pm 1$%. For some applied fields we have evidence that the cylinder exists in a mixed state with bands along the length in states differing by one flux quantum.

A model is proposed consisting of domains with alternating circulation along the length to account for observations of flux trapped by superconducting cylinders in amounts intermediate between flux quanta. The domains are shown to be metastable once they are established, and two mechanisms for nucleating domains are discussed.

The current-voltage characteristics of superconducting weak links are measured near their transition temperature. The effect of thermal fluctuations on these characteristics is found to be in excellent agreement with a calculation of Ambegaokar and Halperin.

The transmission of microwaves through thin (≤ 150 Å) Pb films indicates considerable excess conductivity at temperatures below the superconducting transition temperature. This excess conductivity is interpreted as evidence for fluctuations in the order parameter below $T_c$.

The Compton profile of polycrystalline titanium has been measured at Mo $K\alpha$ ($\lambda =0.709\mathrm{}$ Å). The valence-electron momentum density evidences significant $4s$ character, and the discontinuity in momentum density associated with the Fermi surface is at 1.08 ± 0.06 a.u. compared with the free-electron value of 1.01 a.u. for four electrons per atom. Band-momentum wave functions are unavailable for comparison with theory.

Raman scattering data for KCl:${\mathrm{Tl}}^{+}$ crystals are reported. The dominant scattering amplitudes are attributed to vibrations having $E_g$ and $T_{2g}$ symmetry about the ${\mathrm{Tl}}^{+}$ ion. Comparison of the data with theory suggests a small change in interatomic force constants which can be understood in terms of Coulomb and repulsive forces. The ${\mathrm{Tl}}^{+}$-Cl equilibrium spacing in the electronic ground state appears to be consistent with the value computed by Williams.

We show that many properties of bound hole states in cubic semiconductors are strongly modified by coupling to local distortions of the lattice through the dynamic Jahn-Teller effect. We compute reductions in the deformation potentials and $g$ factors caused by coupling to lattice modes of symmetry $E$ and $T_2$ and show that even small coupling strengths produce significant effects. We discuss several examples.

An extra luminescence band is observed in CdS, CdSe, and ZnO under intense illumination by laser light. It is suggested that the additional luminescence arises from a particular exciton-exciton interaction process common to these semiconducting compounds.

It is shown that the thermoelectric power of Ni as a function of temperature exhibits a minimum followed by a maximum in the same temperature interval in which a deviation from the logarithmic temperature dependence of the $\alpha \mathrm{}\left(T\right)=\frac{d\rho \mathrm{}\left(T\right)\mathrm{}}{\mathrm{dT}}$ curve was observed. In other samples of the same purity the $\alpha \mathrm{}\left(T\right)\mathrm{}$ curve did not show any deviation from the logarithmic temperature dependence and the thermoelectric power is a monotonic function of the temperature.

Neutron-scattering experiments show evidence of long-range magnetic polarization of the palladium matrix in dilute ferromagnetic Pd(Ni) alloys. The measured cross sections, for alloys containing up to 4.7 at.% nickel, are interpreted in terms of a model in which the concentration of ferromagnetically aligned giant moments is less than the concentration of nickel atoms.

The specific heat of Au:Co alloys down to 0.02 K is reported. The nuclear term ($A{T}^{-2\mathrm{}}$) is due to the magnetic Co atoms which are found to be those included in groups of three and more neighbors. The low-temperature linear term ($\gamma T$) is the sum of the contributions of the magnetic Co groups, nonmagnetic pairs, and isolated atoms. We estimate fluctuation temperatures of 50 K for the pairs and 700 K for the isolated atoms.

Static quadrupole moments of the first excited states of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ have been measured using the reorientation effect in projectile Coulomb excitation. The results obtained are $Q({}_{}{}^{28}{}_{}{}^{}\mathrm{Si}, 2^{+})=+0.11\mathrm{}\pm 0.05$ b, $Q({}_{}{}^{32}{}_{}{}^{}\mathrm{S}, 2^{+})=-0.20\mathrm{}\pm 0.06$ b, and $Q({}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}, 2^{+})=+0.01\mathrm{}\pm 0.04$ b.

The cross section for the $1h_{\frac{9}{2}}-1\mathrm{}{i}_{\frac{13}{2}}$ single-proton transition in the reaction ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(p, p^{\prime }){}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}_{}^{*}{}_{}{}^{}$ at 39.5 MeV has been measured. It is shown that most of the observed cross section is due to admixtures of the state formed by coupling the valence proton of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ to the highly collective $3^{-}$ state of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at 2.614 MeV. An estimate of core polarization, based on the work of Kuo and Brown, grossly underestimates the $L=3\mathrm{}$ component of the cross section.

The effects of pairing correlations on the ground-state band of ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ are investigated. It is shown that the computed low-lying excited-state spectrum is significantly affected, whereas the $E2\mathrm{}$ transition probabilities are almost unaffected by the pairing correlations.