We have measured the hyperfine field at ${}_{}{}^{100}{}_{}{}^{}\mathrm{Rh}$ impurity nuclei in a ferromagnetic Ni host in the region just below the Curie temperature, using time-differential perturbed $\gamma \gamma$ angular correlations. We obtain a single-valued critical exponent of $\beta =0.385\mathrm{}\pm 0.005$.

We have made detailed measurements of the variation of the electrical resistivity in the vicinity of the critical temperature and composition of the liquid alloys Hg-Ga and Bi-Ga. Anomalies are observed in the temperature dependence of resistance at up to 10°C above the critical temperature in the Bi-Ga system and up to 2°C in the Hg-Ga system.

A calculation of the phonon frequencies of the $\beta -\mathrm{W}$ structure crystals shows that long-wavelength optic-mode instabilities occur. These are associated with a high density of electronic states in the transition-metal $d$ bands. The $\Gamma _{15}^{}{}_{}{}^{\mathrm{}(-)\mathrm{}}$ and $\Gamma _{25}^{}{}_{}{}^{\mathrm{}(-)\mathrm{}}$ optic modes soften: these are consistent with a second-order structural phase transition.

Measurements of the second derivative of the photoelectron energy distribution from cesiated Cu reveal structure not discernible in the energy distribution itself. The behavior of the structure on varying the photon energy is in excellent agreement with calculations based on $\overrightarrow{\mathrm{k}}$-conserving transitions within an interpolated band structure.

The dielectric constant of amorphous selenium is calculated in the region from 2 to 10 eV using a pseudopotential formalism to calculate "lifetimes" of electrons in the amorphous state. Spicer's "nondirect transition" model is checked and modified to include energy-dependent matrix elements.

A basic calculation of the work function and a surface potential of a single-crystal plane is presented. This first theory provides quantitative results for W(110). Smoluchowski's model is used to determine an effective surface pseudopotential, and many-electron effects are included self-consistently and beyond the local-density approximation through a gradient-expansion formalism. Some limitations of the local-density approximation are revealed. Another explanation for the experimental work-function anomaly is offered.

We have observed new "local-mode lattice vibrations" in GaP, both in Raman scattering and as cooperating phonons in optical transitions. The modes are best qualitatively described as a particle—the LO phonon —bound to a neutral donor, which provides an effective attractive interaction for the phonon. In this analogy, bound states having various angular momenta around the donor can be expected, and both $S$ and $P$ states have been identified experimentally.

Guest-host-guest exciton exchange (superexchange) is appreciable in the ${}_{}{}^1{}_{}{}^{}B_{2\mathrm{u}}^{}{}_{}{}^{}$ state of a ${\mathrm{C}}_{10}$${\mathrm{H}}_8$-${\mathrm{C}}_{10}$${\mathrm{D}}_8$ mixed crystal. The experimental resonance pair fine structure in this system has been satisfactorily fitted, resulting in three sets of six pairwise exciton interactions, consistent with all known experimental data. A point multipole expansion, limited to nonoverlapping charge distributions and truncated after the transition-octupole-transition-octupole term, is only consistent with one set, whose values are presented. Using these values, the exciton band structure is completely determined within the restricted Frenkel limit.

The hyperfine fields at Ca in ferromagnetic metals have been studied by time-differential measurements on the 3.19-MeV $6^{+}$ state in ${\mathrm{Ca}}^{42}$. The observed hyperfine field in Fe was $H_{\mathrm{hf}}=-100\mathrm{}\pm 9$ kG; preliminary results in Co indicated $H_{\mathrm{hf}}=-70\mathrm{}\pm 15$ kG and in Ni suggested $\left|H_{\mathrm{hf}}\right|<\mathrm{}30\mathrm{}$ kG. These results are in disagreement with predictions by Balabanov and Delyagin. A time-integral measurement in an external magnetic field yielded $g\left(6^{+}\right)=-0.42\mathrm{}\pm 0.03$. The mean lifetime of the $6^{+}$ state was remeasured to be $\tau =7.65\mathrm{}\pm 0.23$ nsec.

Some measurements of ($p,t$) differential cross sections are reported for which a conventional distorted-wave Born-approximation analysis does not work well, and where the findings suggest caution in the interpretation of ($p,t$) studies in the $A=50\mathrm{}$ mass region at a bombarding energy of about 27 MeV.

Measurements of neutron polarization are reported for the reaction $\mathrm{T}\mathrm{}(d,n)\mathrm{}{}_{}{}^4{}_{}{}^{}\mathrm{He}$ at 0° in which the incident beam is polarized with quantization axis perpendicular to the direction of motion. The beam polarization was described by $p_3=p_{33}\approx 0.76$, while beam intensities varied from 10 to 40 nA. At $E_d=15\mathrm{}$ MeV the neutron polarization was measured to be +0.56±0.036 with respect to the quantization axis. At 3.9 MeV the polarization was zero, showing the influence of spin-flip interactions from the low-energy ${}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{}$ resonance. The measurements are related to polarization transfer and efficiency tensor functions for the reaction.

Mass relationships are used to compute the energy of quartet excited states in $N=Z$ even-even nuclei for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ up to ${}_{}{}^{52}{}_{}{}^{}\mathrm{Fe}$. The states obtained are quasibound up to excitation energies of about 40 MeV and could account for the narrow structures recently observed in heavy-ion transfer experiments.

Gamma rays from resonance neutron capture in ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ were detected in the neutron energy range 40 eV-1 keV. The resonance energy dependence of the radiative transition intensities to the low-lying levels shows a nonstatistical structure. This structure is found to be correlated with the local neutron strength function.

In a sample of 8300 events of the type ${\pi }^{-}+p\to {\pi }^{-}+{\pi }^{+}+n$ obtained from a hydrogen bubble chamber exposure, a strong sharp $\omega \to {\pi }^{-}+{\pi }^{+}$ peak is observed. Analysis indicates that this $\omega \to 2\pi$ decay interferes almost perfectly constructively with the prominent decay of ${\rho }^0\to {\pi }^{-}+{\pi }^{+}$. The interference phase is determined to be -15°±30°. This phase is consistent with predictions of $\pi -B$ degeneracy using Regge-pole methods.

The reaction ${\gamma }_{\perp ,\parallel }p\to {\pi }^{+}n$ has been studied with linearly polarized photons of energy 3.0 GeV at $-t$ values between 0.15 and 1.2 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$. The asymmetry $A^{+}=\frac{(d{\sigma }_{\perp }-d{\sigma }_{\parallel })}{(d{\sigma }_{\perp }+d{\sigma }_{\parallel })}$ is found to be positive throughout this four-momentum-transfer range, implying the dominance of natural parity exchange in the $t$ channel. Comparison of $d{\sigma }_{\perp }({\gamma }_{\perp }p\to {\pi }^{+}n)$ and $d{\sigma }_{\perp }p\to {\pi }^{-}p$) from a previous experiment indicates strong interference between the isoscalar and isovector photon amplitudes for photons polarized perpendicular to the production plane.

The $K_L-K_S$ mass difference, $\Delta m\equiv \frac{(M_L-M_S)c^2}{\hslash }$, has been redetermined in a high-statistics experiment performed at the zero-gradient synchrotron of Argonne National Laboratory, using the "gap method" originally developed at Princeton. Two independent measurements, using ${\mathrm{B}}_4$C and Cu, respectively, as regenerators, were performed and gave consistent results. Their mean is $\Delta m=(0.542\mathrm{}\pm 0.006)\times {10}^{10}$ ${\sec }^{-1\mathrm{}}$. With this value, the result of our recent determination of arg ${\eta }_{+-}$ by "vacuum regeneration" is recalculated to be (44.7 ± 5.0)°, where the error allows for the uncertainty in $\Delta m$ given above.

We determine the absorption coefficient and polarization selection rules for photon splitting in a strong magnetic field, and describe the possible application of our results to pulsars.

Recent measurements of neutron-proton charge-exchange scattering showed a change in the behavior of the cross section at $u=0\mathrm{}$, near the one-pion threshold. The slope of the backward cross section also increased rather rapidly, with a maximum also near the one-pion threshold. We point out that the one-pion-exchange amplitude, interfering with a slowly varying amplitude at $u=0\mathrm{}$, gives qualitatively the same behavior as observed in the experiments. A similar explanation has been suggested as an explanation for the $n-p$ charge-exchange data above 2 GeV.

We present a new scaling law and empirical formulas for the double differential cross section of secondary production between 10 and 70 BeV. The 0° momentum spectrum is found to scale according to the square root of the incident momentum, thus reflecting the importance of the c.m. system in the pionization process. It is pointed out that the 70-BeV production data of the Serpukhov-CERN collaboration experiment are very likely too low by a factor of ∼ 2.5.

Remarks are made about the hypothesis of limiting fragmentation. In particular, the concept of favored and disfavored fragment distribution is introduced. Also a sum rule is proved leading to a useful quantity called energy-fragmentation fraction.