Optical pumping of neon metastable atoms in a helium-neon discharge has been accomplished in a manner similar to that for helium. Metastable neon has a $P$ configuration and was expected to have a large spin-disorientation cross section; however, the depolarization cross section is less than 5.4 × ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$. The measured $g$ factor is $g_J=1.50152\mathrm{}\pm 0.00064$.

Light scattering attributable to a change in polarizability produced in colliding pairs of atoms is observed in gaseous Ar and Kr. The experimental results are qualitatively accounted for by relations between the integrated intensity and the collision-induced polarizability.

${\mathrm{H}}^{-}$ and ${\mathrm{D}}^{-}$ ions produced by dissociative attachment of electrons to ${\mathrm{H}}_2$O and ${\mathrm{D}}_2$O have been used as primary ions in the measurement of a cross section of (1.6 ± 0.3) × ${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$ for the negative-ion-molecule reaction ${\mathrm{H}}^{-}$ + ${\mathrm{H}}_2$O → ${\mathrm{OH}}^{-}$ + ${\mathrm{H}}_2$ at an ${\mathrm{H}}^{-}$ energy of 1.93 ± 0.45 eV and (5.8 ± 1.2) × ${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$ for the reaction ${\mathrm{D}}^{-}$ + ${\mathrm{D}}_2$O → ${\mathrm{OD}}^{-}$ + ${\mathrm{D}}_2$ at a ${\mathrm{D}}^{-}$ energy of 1.84 ± 0.38 eV. The method is quite generally applicable to the study of negative-ion reactions in the energy region from thermal energies to ∼3 eV.

The production of a spark by focusing a single subnanosecond laser pulse in air and other gases has been investigated. Streak photographs reveal that the plasma development is significantly different from that observed with conventional $Q$-switched laser pulses. Preliminary studies of the pressure dependence of the breakdown threshold in argon and nitrogen are reported.

The optical saturation of atomic laser transitions depends upon two linewidths ${\Gamma }_1$ and ${\Gamma }_2$ which have not been independent observables in previous experiments. We have obtained an independent measurement of the linewidth ${\Gamma }_1$ while observing magnetic resonance in a stimulated-emitting state.

The electrical conductivity of a highly turbulent plasma is measured in the electron density range ${10}^{10}$-${10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$, using hydrogen, argon, and xenon. When the applied electric field is large (≳ 100 V ${\mathrm{cm}}^{-1\mathrm{}}$), it is found that the conductivity may be described by the formula $\sigma \approx \frac{1}{2}{\left(\frac{M}{m}\right)}^{\frac{1}{3}}{\omega }_{\mathrm{pe}}$, which was first suggested by Buneman.

Measurements of the magnetic susceptibility of very dilute solid solutions of ${\mathrm{He}}^4$ in ${\mathrm{He}}^3$ as a function both of molar volume and of ${\mathrm{He}}^4$ concentration in the $\alpha$ phase have been made between 1 and 0.04°K by steady-state nuclear-resonance techniques. The most dilute solution (5 × ${10}^{-7\mathrm{}}$ ${\mathrm{He}}^4$) followed Curie's law over the range in molar volume (23.0-21.0 cc) measured. The less dilute solutions (1 × ${10}^{-4\mathrm{}}$ and 3 × ${10}^{-4\mathrm{}}$ ${\mathrm{He}}^4$) followed a Curie-Weiss law with relatively large, antiferromagnetic Weiss constants.

Measurements of the linear thermal expansion coefficient $\alpha$ of Gd crystals have shown that $T_c$ as well as the temperature dependence of $\alpha$ is a function of the electron-impurity mean free path. These results have allowed us to infer the temperature dependence of the coherence length $\xi$.

Coherent exchange scattering has been observed in low-energy electron diffraction from antiferromagnetic NiO. Half-order diffraction beams which correspond to the translational symmetry of the magnetic cell occur below the Néel temperature, $T_{\mathrm{N}}=525\mathrm{}$°K, and disappear at $T_{\mathrm{N}}$. These beams are attributed entirely to exchange scattering because of their intensity, which is much too great to be accounted for by direct dipole-dipole and spin-orbit interactions.

A study of both thick-crystal and thin-film optical absorption data for the thallous halides (CsC1 crystal structure) indicates a direct band gap associated with the excitation of the thallous rather than the halide ions. Extremely narrow and very strong exciton lines exhibiting sidebands have been observed in thin films which are relatively free of strain. A very small exciton binding energy, a high polarizability, and large electron-lattice interaction favor this sideband structure which is probably due to coupled exciton-phonon states.

The shifts of the first two exciton peaks with hydrostatic pressure have been measured in CsI films at 78°K and found to be linear. The deformation potentials deduced are -2.10 eV and +2.10 eV, respectively. These results confirm Onodera's assignment of the two peaks to excitons derived from bands of different symmetry. The data indicate that above 7 kbar the conduction bands cross and the ${\Gamma }_{12}$ level lies below the ${\Gamma }_1$ (Onodera's assignment).

The size distribution of noncatastrophic flux jumps in cylindrical specimens of Pb + 2 at.%-In alloys in an axial, homogeneous, linearly swept magnetic field has been measured as a function of field at 4.2°K and found to approximate the form $N\left(\varphi \right)=N\left(0\right)\mathrm{}\times \exp (-\frac{\varphi }{\overline{\varphi }})$, where the mean bundle size $\overline{\varphi }$ was of the order of ${10}^2{\varphi }_0$ to ${10}^4{\varphi }_0$. The fraction of the entering flux participating in the jumps was found to have a field dependence similar to that of $\overline{\varphi }$. When surface superconductivity was present, the jumping persisted up to $H_{c3\mathrm{}}$.

Measurements of the Hall resistivity in cadmium and cadmium-zinc-alloy single crystals (up to 1.5 at.% Zn) indicate that scattering of carriers between two adjacent branches of the hole surface is possible and that this intersheet scattering can affect the galvanomagnetic properties very markedly.

Two- and four-prong final states in a 28.5-GeV/c $p-p$ bubble-chamber experiment were examined for single-isobar production in various decay channels; results are compared with missing-mass-spectrometer data. The 1400 enhancement was found to be an $N\pi$ system with the ratio $\frac{n{\pi }^{+}}{p{\pi }^0}\sim 2$, which establishes the isospin assignment $I=\frac{1}{2}$. The final state ${\Delta }^{++}\mathrm{}\left(1238\right)n$ was measured and compared with low-energy data to show that the cross section decreases according to $P_{\mathrm{lab}}^{}{}_{}{}^{-(1.91\mathrm{}\pm 0.08)}$, consistent with single-pion exchange.

Experimental distributions in all kinematic variables for the reaction $\mathrm{pp}\to \mathrm{pn}{\pi }^{+}$ at 28.5 GeV/c are consistent with predictions of a double-Regge-pole model employing Pomeranchuk and pion exchanges with the pion required to couple in conspiracy fashion to $\mathrm{np}$. The 1400-MeV $\pi N$ enhancement seen in these data is well fitted.

Applying the technique of finite-energy sum rules to the recent CERN $\pi N$ phase-shift analysis, we investigate the Regge structure of $B^{\mathrm{}(-)\mathrm{}}$ at large momentum transfer. The features found are most easily explained by an additional fixed pole at $\alpha =-1\mathrm{}$. Some of its implications are discussed.

We consider vector and pseudoscalar meson decays using vector gauge fields with current mixing. The processes $\omega \to 3\pi$, $\omega \to \pi \gamma$, and $\pi \to 2\gamma$ are fitted with one value of the gauge field's coupling $g$, which also determines leptonic decay rates of vector mesons. Octet breaking of the underlying $\mathrm{VVP}$ strong interaction introduces four parameters. The available experimental information on $\pi$, $\eta$, $\omega$, and $\varphi$ decays gives relations among these parameters which predict rates for decays such as $K^{*}\to K\gamma$.

We present results pertaining to threshold $\pi$ production in nucleon-nucleon collisions, obtained in the soft-pion approximation. A typical result is ${\sigma }_{\mathrm{tot}}(pp\to \mathrm{np}{\pi }^{+})=24\mathrm{}$ μb at $T_{\mathrm{lab}}=310\mathrm{}$ MeV, in good agreement with extrapolations from higher energy data.

The optical nutation effect has been observed on a rotational-vibrational transition in gaseous S${\mathrm{F}}_6$ at 10.6 μ.

The excess pressure due to phase separation of solid ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures held at constant volume has been measured. From this we obtain the phase-separation temperature as a function of the mole fraction, the excess volume, and the pressure dependence of the critical temperature.