An exact shell-model calculation is presented that gives a good description of the properties of ${\mathrm{O}}^{16}$ and neighboring nuclei.

We point out the importance of the random fluctuations in astrophysical magnetic fields, which lead among other things to rapid diffusion of energetic particles across the average magnetic field. Application to the interplanetary magnetic field leads to a theory in which the field-line random walk, measured by the observed power spectrum of field fluctuations, is in agreement with that deduced from the observed turbulent motions in the solar photosphere. The two determinations agree well with the recently observed spread in longitude of low-energy particles released at the sun.

The reaction ${\pi }^{+}p\to {\pi }^{+}{\pi }^{-}{\pi }^0{\Delta }^{++}$ has been studied in the range 3-4 GeV/c of incident pion momenta. Results suggest that the origin of the $H$ enhancement is purely a kinematic one that arises from the $\rho$-band cut in an essentially structureless three-pion Dalitz plot.

A sum rule for the $I=2\mathrm{}$ amplitude at the symmetry point, $s=t=u=\frac{4}{3}m_{\pi }^{}{}_{}{}^2$, is written down with the assumption that the amplitude satisfies an unsubtracted fixed-energy dispersion relation. This sum rule can be saturated by the $S$ waves and the $\rho$ and $f^0$ mesons. The known crossing relations at the symmetry point connecting the value and the derivative of the $I=0\mathrm{}$ amplitude to those of the $I=2\mathrm{}$ amplitude are then used to show that the $I=0\mathrm{}$ $S$-wave scattering length must be small and negative.

From Rayleigh linewidth and intensity studies by means of quasielastic light scattering, we report a diffusion coefficient of the form $D=d{\left[\right(\frac{T}{T_P})-1+t_{\Gamma }]}^{{\gamma }^{*}}$ for solutions of isobutyric acid in water in the neighborhood of the critical solution concentration. While $d$ and ${\gamma }^{*}\left(\cong \frac{2}{3}\right)$ remain constant within the concentration range of our investigation, $t_{\Gamma }$ depends upon concentration and vanishes at the critical solution concentration. Our results are discussed in terms of the critical-point exponents.

We have measured the linewidth of light Brillouin scattered from C${\mathrm{O}}_2$ for $0.015<~T-T_c<~15$ °C. As $T_c$ is approached from high temperature, the linewidth increases rapidly but then saturates at $T-T_c\approx 1$ °C and remains roughly constant to $T-T_C=0.015\mathrm{}$ °C. These results are discussed in the light of the dynamic scaling laws.

We describe an experiment which indicates that the addition of ${\mathrm{He}}^3$ impurities to superfluid helium has a pronounced effect on the velocity at which negative ions produce vorticity (vortex rings). The ${\mathrm{He}}^3$ impurities have no effect, however, on the creation of vorticity by positive ions.

Experiments in which a modulating magnetic field has been superimposed on the steady magnetic field necessary to observe the thermomagnetic gas torque effect have yielded a twofold behavior. For magnetic fields below that for maximum torque, a frequency-dependent torque reduction $\Delta N$ is observed. For magnetic fields equal to or somewhat greater than that for maximum torque, a second effect is superimposed on the first: an absorptionlike peak which occurs at frequencies proportional to the magnetic field strength.

We report measurements of the velocity of second sound near $T_{\lambda }$. It is found to vanish with the 0.386 power of $T_{\lambda }-T$. The results confirm the theoretical expression and permit a direct asymptotic comparison for the first time of independent but theoretically equal quantities.

Measurements of demagnetization factors of cerous magnesium nitrate thermometers show that a recent criticism of liquid ${\mathrm{He}}^3$ and ${\mathrm{He}}^3$-${\mathrm{He}}^4$ experiments is not applicable.

The nuclear spin-lattice relaxation time $T_1$ of ${\mathrm{V}}^{51}$ in a type-II superconductor ${\mathrm{V}}_3$Sn has been measured as a function of temperature as well as magnetic field. In the case of $T_c\mathrm{}\left(0\right)>T_c\mathrm{}\left(H\right)>0.6\mathrm{}{T}_c\mathrm{}\left(0\right)\mathrm{}$, the temperature variation of $T_1$ shows a minimum just below the critical temperature corresponding to the magnetic field in which $T_1$ was measured, $T_c\mathrm{}\left(H\right)\mathrm{}$, and then increases gradually. In the case of $T_c\mathrm{}\left(H\right)<0.6\mathrm{}{T}_c\mathrm{}\left(0\right)\mathrm{}$, just below $T_c\mathrm{}\left(H\right)\mathrm{}$ corresponding to that field, $T_1$ shows no minimum but increases monotonically.

It is shown that the Stark ladder for conduction electrons in a constant electric field does not follow from the existing theory. The former proofs of the ladder are shown to be based on inconsistent assumptions. A discussion is given of a tight-binding model which leads to a ladder when overlap is completely neglected.

Measurements of the spin-resonance linewidth for Mn in dilute copper alloys provides evidence of the extended nature of the magnetic impurity wave function in the metal and allows a straightforward determination of the $s-d$ admixture $V_{\mathrm{dk}}\simeq 1$ eV. A theoretical treatment of the local moment spin relaxation via the distant impurity spin-orbit interaction is given.

It is shown that the good agreement between theory and experiment which Watson, Bennett, and Freeman claim in a recent paper on the origin of solvent Knight shifts in alloys does not exist and that consequently one cannot conclude that their results per se point to deficiencies in other methods of evaluating Knight shifts.

It is shown that Fermi-liquid interactions in the alkali metals lead to a family of long-wavelength electromagnetic modes propagating parallel to a uniform magnetic field, near the cyclotron frequency. In contrast to the perpendicular case, however, there is a cutoff wavelength that increases with decreasing Fermi-liquid interaction, and can be in the range of 10 to 100 cyclotron radii, for the size of interaction now indicated in potassium.

The thermodynamics of transitions between uniformly and nonuniformly magnetized states of an isotropic ferromagnet in an external field is described in the molecular-field approximation. These results are found to be in substantial agreement with many experiments.

Observation of second-harmonic ($2\omega$) generation and mixing in damped Alfvén-wave propagation in pure bismuth, and in helicon propagation in tellurium-doped bismuth, is reported.

The two low-temperature metastable phases of gallium have superconducting energy gap to transition temperature ratios, $\frac{2{\Delta }_0}{k{T}_c}$, of 4.5 for "amorphous" gallium and 3.9 for the crystalline phase, $\beta$-Ga. Beta-gallium shows considerable structure in the tunneling current indicating the presence of several well-defined peaks in the phonon density of states. Structure observed in the "amorphous" gallium tunneling current appears to be a smeared-out version of that observed in $\beta$-Ga.

A number of peaks in photoconductivity have been observed in $n$-type InSb when the impurity-shifted cyclotron resonance frequency is near the longitudinal optical phonon frequency. Certain of these peaks are interpreted as due to photon absorption resulting in the creation of an LO phonon and simultaneous excitation of the electronic impurity state. We present a theory based on the Fröhlich-type electron-phonon interaction.