The equilibrium constant of the ion-pairing reaction ${\mathrm{Li}}^{+}$ + ${\mathrm{B}}^{-}$ ↔ LiB in silicon has been determined by Hall-effect measurements. The result can be expressed as $K=A\times \exp \left(\frac{E}{\mathrm{kT}}\right)$ with $A=21\mathrm{}$ and $E=0.39\mathrm{}$ eV.

There have been a series of optical experiments recently in which two magnons are created on or near an impurity in an antiferromagnet. It is shown that if at least one of these magnons is localized around the impurity, the three-body problem reduces to a series of effective two-body problems. Green's function methods have been used to calculate the line shapes for ${\mathrm{Ni}}^{++}$-doped RbMn${\mathrm{F}}_3$ and KMn${\mathrm{F}}_3$, giving good agreement with experiment.

We report the discovery of a localized enhancement of the Lorenz function in the vicinity of the Néel point of chromium. It is believed to be a manifestation of the inelastic scattering processes that occur due to the critical fluctuations in the spin-density-wave system resulting in an augmentation of the electron and spin-wave thermal conductivities.

We report thermal broadening of the 18418-${\mathrm{cm}}^{-1\mathrm{}}$ purely electronic transition in Mn${\mathrm{F}}_3$ split by an external magnetic field of 25 kOe. A differential broadening of the split line is observed, demonstrating the important role of Raman scattering of magnons as a mechanism for broadening this optical line at low temperatures. A temperature-dependent reduction of the effective $g$ factor is also observed. Calculations based on a simple model give satisfactory agreement with the observations.

It is pointed out that the statement made by Phillips that large discrepancies exist between the observed cohesive energy of certian crystals and the values calculated by the electronegativity-difference equation is false. The purported discrepancies occurred because of errors in Phillips's calculations.

The question raised by Pauling of the number of single bonds per unit cell of partially ionic semiconductors is discussed in terms of optical spectra. It is argued that the assumption of classical resonance theory that only half the valence electrons in II-VI semiconductors are in bonding states is inconsistent with their optical spectra.

The effects determining the energies of isobaric analog resonances are studied. In particular, the compound and continuum shifts, nuclear two-body correlations, isospin-nonconserving nuclear forces, and isospin impurity are discussed. These effects are important in deriving the excess neutron density from analog-resonance experiments.

Beams of 18-MeV $\alpha$ particles and 70-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ were used for $E3\mathrm{}$ Coulomb excitation of the weak-coupling $3^{-}|h_{\frac{9}{2}}〉$ septuplet $J^{\pi }={\frac{3}{2}}^{+}, \cdots , \frac{15}{2^{+}}$ at 2.6 MeV in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. A complete decay scheme was obtained and short lifetimes were determined from observed Doppler effects. We deduce several absolute transition probabilities for both excitation and decay involving the multiplet and low-lying single-particle states.

Using the Princeton-Pennsylvania Accelerator rapid-cycling bubble chamber in a flash-lamp triggered mode we have observed backward (${\pi }^{+}{\pi }^{-}$) and (${\pi }^{+}{\pi }^{-}{\pi }^0$) multipion production in the reaction ${\pi }^{+}n\to pm\left(\pi \right)$ at 2.15 BeV/c. The main characteristics of the data are a sharp forward peaking of the proton relative to the incident ${\pi }^{+}$ direction for all multipion masses below 1100 MeV/c and the strong production of the $\omega$ meson. Backward $\omega$ production is observed to be more probable than backward $\rho$ production. The sharp forward peaking of the proton in these reactions is suggestive of the dominance of baryon exchange.

Preliminary measurements of the transition radiation in the x-ray region indicate that an average of 12 x-ray photons are produced by a single positron of 2-BeV energy traversing a stack of 231 thin aluminum foils. This number is large enough to indicate that it is feasible to use the x-ray transition radiation for the determination of the relativistic factor $\gamma$ rather than $\beta$ of superhigh-energy particles. Such an application may well provide a unique method for distinguishing monoenergetic particles in the superhigh-energy region.

Preliminary measurements of the transition radiation in the x-ray region indicate that an average of 12 x-ray photons are produced by a single positron of 2-BeV energy traversing a stack of 231 thin aluminum foils. This number is large enough to indicate that it is feasible to use the x-ray transition radiation for the determination of the relativistic factor $\gamma$ rather than $\beta$ of superhigh-energy particles. Such an application may well provide a unique method for distinguishing monoenergetic particles in the superhigh-energy region.

A nearly monochromatic high-energy photon beam produced by Compton backscattering of ruby laser light has been used to study photoproduction in a hydrogen bubble chamber. The total hadronic $\gamma p$ cross sections at 1.44, 2.8, and 4.7 GeV are found to be 145.1 ± 5.7, 131.3 ± 4.3, and 124.2 ± 3.9 μb, respectively. Partial cross sections are presented also.

A weak-interaction Hamiltonian is presented which can account in a unified way for the $\mathrm{CP}$ nonconservation observed in $K_L$ decay and for a possible lepton nonconservation associated with nuclear double-beta decay.

It is shown that the forward peak in the differential cross section for positive-pion photoproduction can be explained with Veneziano representation for the appropriate amplitude.

Elastic scattering of $\overline{p}$ on $p$ has been studied for ${cos\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ between -0.88 and -1.0 and $P_{\mathrm{lab}}\left(\overline{p}\right)$ between 0.70 and 2.16 GeV/c. The momentum dependence of the cross section shows a sharp dip at 0.9 GeV/c and a broad peaking around 1.4 GeV/c. The possibility of the peak resulting from direct formation of boson resonances has been studied. Alternatively, a diffraction model agrees qualitatively with our data and other elastic data at different angles.

Rotational excitation of homonuclear diatomic molecules can be simply yet accurately calculated from the scattering parameters of elastic electron-molecule scattering in the fixed-nuclei approximation. The total scattering cross sections for $\Delta j\ne 0$ transitions are independent of $s$-wave parameters, and ratios of $\Delta j=\pm 2$ cross sections agree with experimental results in ${\mathrm{H}}_2$ and with rotational close-coupling calculations. Absolute total and differential cross sections can be explained.

Results showing the attenuation of second sound due to the flow of He II film from a beaker into a resonant cavity are presented. The attenuation caused by the film flow is found to depend on the height above the cavity of the bulk He II level in the beaker. These results are interpreted in terms of vortices which are carried by the film into the resonant cavity.

Some absorption lines of rare-earth ions in calcium fluoride were found to be considerably affected by irradiation with x rays. These narrow lines, which appeared superimposed on a broad background of color-center absorption, were in some cases over 100 times stronger after irradiation and had strongly asymmetric line shapes, often resulting in an antiresonance dip. It is proposed that these effects are caused by interaction of the rare-earth ion and a neighboring color center.

The anomalies present in the electrical resistivity of Ce${\mathrm{Al}}_2$ have been suppressed by partial replacement of Ce by Th. It is argued that this substitution influences appreciably the density-of-states function of the conduction electrons at the Fermi surface. The result of the Th substitution is thought to bring further evidence in favor of the occurrence of the Kondo effect in Ce${\mathrm{Al}}_2$.

The influence of free-carrier screening of the Coulomb interaction on bound states of excitons in crystals is investigated. The dependences of the ground-state energy and oscillator strength of the free-carrier concentration are obtained within the effective mass formalism employing a screened Coulomb potential. The results are used to successfully predict CdS modulated reflectance line shapes as a function of free-carrier concentration.