Presented herein is a second-quantized formulation for a system of interacting nuclei and electrons expressed in terms of the creation and annihilation operators of various species of atoms and ions which can be formed by combining various numbers of the "elementary" particles. Processes such as ionization and recombination appear naturally. Explicit expressions for interatomic forces including exchange effects are generated from a "cluster expansion" reminiscent of the Ursell expansion.

New boundary conditions on the Einstein-Rosen-Bondi gravitational-wave metrics yield closed inhomogeneous universes which solve Einstein's vacuum field equations exactly. Space sections of these universes have either the three-sphere topology $S^3$ or the wormhole (hypertorus) topology $S^1\otimes S^2$.

We have measured the photon asymmetry parameter for radiative $\mu$ capture in ${\mathrm{Ca}}^{40}$, for photon energies from 57 to 75 MeV. The result obtained seems inconsistent with predictions based on the $V-A$ theory.

The spin-orbit interaction and the correction to the dipole transition moment due to core polarization are included in a calculation of the potassium photoionization cross section. The computed spin orientation of photoejected electrons (Fano effect) and the behavior of the cross section in the region of its minimum are in harmony with recent measurements.

The differential cross section for the electron-impact excitation of the $b{}_{}{}^1{}_{}{}^{}\Sigma _g^{}{}_{}{}^{+}$ state from the ground state of ${\mathrm{O}}_2$ is found to decrease rapidly as the scattering angle approaches zero. This behavior is the diatomic-molecule analog of "parity-unfavored" transitions in electron-atom scattering. A group-theoretic argument is given which explains the observations and provides a selection rule for ${\Sigma }^{+}\leftrightarrow {\Sigma }^{-}$ transitions in diatomic molecules.

The sodium $D$ resonance lines have been studied in saturated absorption with a repetitively pulsed tunable dye laser. The hyperfine splitting of the $3{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ and $3{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ states of ${\mathrm{Na}}^{23}$ is resolved. Measurements with a delayed probe reveal a remanent hole burning in the velocity distributions of the two ground-state levels, caused by a velocity-selective optical pumping cycle. A time-resolved observation of the collisional-velocity thermalization in the presence of Ar buffer gas is reported.

We report the observation of laser emission in optically excited CdSn${\mathrm{P}}_2$:Ag at a threshold of ∼50 ${\mathrm{k}\mathrm{W}/\mathrm{c}\mathrm{m}}^2$ at 20°K. From a study of the magnetic-field-induced shift in wavelength of the spontaneous and stimulated emission, the recombination mechanism is identified as band to band in a regime where electron-hybrid-plasmon (plasmaron) coupling is dominant. This is the first observation of plasmaron coupling in semiconductor laser action, and the first unambiguous experimental evidence for plasmaron coupling in semiconductors.

Evidence is presented that below a rather large angular velocity, ${\omega }_{c1\mathrm{}}$, there is a vortex-free state in rotating locked helium, which we call the Landau state. This is similar to the Meissner state in superconductors. We further show that all the properties of the rotating helium have counterparts in irreversible type-II superconductors and find that ${\omega }_{c2\mathrm{}}$ (analogous to $H_{c2\mathrm{}}$) greatly exceeds our high speeds of rotation.

Nonlinear Landau damping and growth have been observed for ion-acoustic waves. The measured nonlinear wave-wave coupling coefficients are in reasonable agreement with theory. The forced beat oscillations between the two injected waves, which cause non-linear Landau damping, were also observed.

The magnetic field dependence of the stress changes associated with the normal-to-superconducting-state transition was measured for single crystals of Pb-5 at.% In and Pb-10 at.% In, and was found to be in agreement with the magnetic field dependence of the ultrasonic wave attenuation in type-II superconductors.

The nuclear quadrupole interaction of the 247-keV level of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ in pure Cd metal has been measured by the time-differential perturbed angular correlation method. The interaction frequency ${\nu }_Q=\left(\frac{e^2\mathrm{qQ}}{h}\right)=125\mathrm{}\left(1\right)\mathrm{}$ MHz at 298°K. A measurement at 77°K shows an increase of ${\nu }_Q$ by 10% instead of a decrease expected from the contraction of the unit lattice of Cd metal.

The Raman scattering spectrum of V${\mathrm{O}}_2$ is reported between 4.2 and 600°K. In the semiconducting monoclinic phase only sharp phonon structure is observed. The metallic rutile phase exhibits a pronounced softening and damping in the observed phonon spectrum. This evidence supports a recently proposed phenomenological mechanism for the semiconductor-to-metal transition.

Basic statistical considerations are shown to imply pronounced effects on many properties of materials having energy-band tails. For extrinsic cases a metallike temperture dependence of the Fermi energy occurs; in consequence, a method is proposed for directly measuring the density of states in the tail. For intrinsic amorphous semiconductors, severe limitations are found for the inference of a sharp mobility edge from temperature-dependent conductivity data.

We have illuminated a liquid-helium cooled, Hg-doped, Ge photoconductor with 10.6-μm radiation at power levels varying by a factor of 2000. The noise temperature was constant at 35°K over this range, in spite of a resistance inversely proportional to power. This temperature has been used to infer a value of 0.135 for the ratio of free-carrier energy-loss time to recombination time.

Experimental study of low-energy electron-diffraction rotation diagrams from the (001) surface of Al reveals the appearance of systematic structure in the specularly reflected beam. This structure does not seem to be associated either with the secondary Bragg features or with the threshold effect. It has been identified as being due to the coupling between an incident beam and a localized surface state. A simple calculation of the $\varphi$ dependence of the resonance minima based on the Kronig-Penney model confirms this conclusion. The resonance intensity profile is generally in agreement with McRae's prediction.

Proton magnetic-resonance measurements are carried out on a single crystal of $\mathrm{Cu}{\left(\mathrm{N}{\mathrm{O}}_3\right)}_2·2\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$ in magnetic fields up to 50 kOe at temperatures below 1 K. The copper ions form pairs with an exchange interaction $-\frac{J}{k}$ of about 5 K. In magnetic fields around 36 kOe the much weaker interpair exchange $J^{\prime }$ leads to short- and long-range order below 0.35 and 0.16 K, respectively. The phase transition at 0.16 K is characterized by a spontaneous component of the time-averaged magnetic moment of the Cu ions perpendicular to the external field, and disappears below 29 and above 42 kOe.

Neutron-scattering measurements have been made of the critical parameters of the simple Heisenberg ferromagnets EuO and EuS. Values of the critical exponents $\beta$ and $\nu$ and the amplitudes of $B$ and $F$ describing, respectively, the reduced magnetization and the inverse correlation range (above $T_c$) are in good accord with theory. The measured values of the exponent $\gamma$, describing the static susceptibility, support the recent prediction that $\gamma \approx 1.40$ in a simple nearest-neighbor Heisenberg ferromagnet. The scaling relation between $\beta$, $\nu$, and $\gamma$ is fulfilled.

The elastic and inelastic form factors for the $0^{+}$, $2^{+}$, and $4^{+}$ states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured. The data were analyzed by treatment of the rotational excitation in the framework of the Nilsson model. We have obtained a single intrinsic state which satisfies simultaneously the observed form factors for the intraband transitions. The deformations were extracted directly from the charge distribution of the intrinsic state.

The angular-momentum dependence of the matrix element which couples the rotational and vibrational bands in deformed nuclei is determined from the measured energies of ground-state band levels. A calculation involving three bands and matrix diagonalization produces excellent overall agreement with experimental $E2\mathrm{}$ transitions between the $\beta$-vibrational, $\gamma$-vibrational, and ground-state-rotational bands, and for transitions within the ground-state band.

The reactions ${\mathrm{He}}^3\mathrm{}(p,pd)p$ and ${\mathrm{He}}^3\mathrm{}(p,2p)d$ have been studied at 35 MeV. A dominant feature of these data is $p-p$ and $p-d$ quasielectric scattering. A plane-wave impulse approximation gives a qualitative fit to the ${\mathrm{He}}^3\mathrm{}(p,2p)d$ data, but fails to explain the ${\mathrm{He}}^3\mathrm{}(p,pd)p$ data. Various possible explanations are discussed.