It is shown theoretically for systems with a special geometry that nucleation of superconductivity can occur for magnetic fields above $H_{c3\mathrm{}}$.

The optical absorption of the sodium halides (NaF, NaCl, NaBr, NaI) has been studied at energies about 30 to 75 eV, i.e., in the neighborhood of the sodium $L_{2,3}$ edge. The intense continuum of the synchrotron radiation emitted by the 6-GeV electron synchrotron has been used as the light source.

Recent measurements of electronic transport properties showing the dominance of electron-electron scattering in transition metals at low temperatures are suggested to have an interpretation in terms of Baber's model.

Photoemission and reflectivity data from copper-rich copper-nickel alloys are presented. A rigid-band model is found not to hold for these alloys; rather the virtual-bound-state model gives a more adequate description of the electronic structure.

The short-range, one-band model for electron correlations in a narrow energy band is solved exactly in the one-dimensional case. The ground-state energy, wave function, and the chemical potentials are obtained, and it is found that the ground state exhibits no conductor-insulator transition as the correlation strength is increased.

Plastic detectors were used to observe angular distributions of fission fragments emerging from a U${\mathrm{O}}_2$ single crystal. In fission induced by thermal neutrons and by 12-MeV protons, characteristic blocking patterns were observed, showing strong attenuations along major crystal axes. This shows that fission occurred while the nuclei were within 0.1 Å of a lattice site and indicates that the total lifetime in 12-MeV proton fission is less than 2×${10}^{-17\mathrm{}}$ sec.

A measurement of delayed coincidences characteristic of muon decay has been made at a depth of 1440-hg/${\mathrm{cm}}^2$ standard rock with a 200-liter liquid scintillation detector. These results are consistent with the decay rate predicted from the depth-intensity curve for the penetrating component of the cosmic rays, providing independent evidence that this component is energetic muons.

The conversion process ${\Sigma }^{+}n\to \Lambda p$ has been observed using the sequence $K^{-}d\to {\pi }^{-}\left({\Sigma }^{+}n\right)\to {\pi }^{-}\left(\Lambda p\right)$. The results of this study are that (1) the conversion process at very low energy is dominated by the ($\Sigma N$) triplet state; and (2) the reaction is strongly enhanced for $\Lambda p$ masses below ${\Sigma }^{+}n$ threshold, suggesting the existence of a bound state in the ${\Sigma }^{+}n$ system and, hence, an elastic resonance in the $\Lambda p$ system.

The two-body radiative decays of nonstrange vector and pseudoscalar mesons are calculated by using the technique of current algebra, partial conservation of axial-vector current, and hard pion and eta. The predictions agree quite well with the available experimental results.

We have found the branching ratio for the electronic decay of the ${\Sigma }^{-}$ to be $\frac{R({\Sigma }^{-}\to n+e^{-}+\overline{\nu })}{R({\Sigma }^{-}\to n+{\pi }^{-})}=(1.11\mathrm{}\pm 0.09)\times {10}^{-3\mathrm{}}$. Similarly, in a measurement of 5×${10}^4$ ${\Sigma }^{+}\to n+{\pi }^{+}$ decays we have found no example of decays of the type ${\Sigma }^{+}\to n+e^{+}+\nu$ or ${\Sigma }^{+}\to n+{\mu }^{+}+\nu$. This gives an upper limit of 6.3% (90% confidence level) on the relative rate $\frac{R(\Delta S=-\Delta Q)}{R(\Delta S=+\Delta Q)}$ for the process in this experiment.

The lifetime of the $2{}_{}{}^1{}_{}{}^{}P$ state of helium has been measured, using a modified Hanle-effect method, as $\tau =(5.8\mathrm{}\pm 0.4)\times {10}^{-10\mathrm{}}$ sec. The oscillator strength for the $2{}_{}{}^1{}_{}{}^{}P-1\mathrm{}{}_{}{}^1{}_{}{}^{}S$ transition determined from the lifetime is $f=0.27\mathrm{}\pm 0.02$.

Observation of the nuclear-acoustic-resonance dispersion mode of ${\mathrm{F}}^{19}$ in antiferromagnetic RbMn${\mathrm{F}}_3$ is reported. Saturation studies indicate that the dispersion mode saturates at higher ultrasonic powers than does the pure absorption mode.

The existence of strong variations in the total secondary electron current with incident beam direction from a tungsten (110) surface can be explained on the basis of the observed angular distribution of the secondary emission and the reciprocity theorem. We propose a dynamical two-beam model based on the variation of electron absorption in the crystal as a function of the diffraction conditions.

The power-dependent suppression of spin-lattice relaxation observed in gadolinium hexa-antipyrene iodide is explained as a suppressed Raman relaxation due to a severely bottlenecked direct process.

The low-temperature susceptibility above the magnetic ordering temperature of La-Ce alloys (Ce concentration ≤ 40 at%) and of $\alpha$-Ce and $\beta$-Ce is proportional to $T^{-\frac{1}{2}}$. This is the temperature dependence recently suggested by Anderson in the case of spin compensation. The susceptibility per Ce atom for the alloys above the magnetic ordering temperature is independent of Ce concentration. It is suggested that these systems exhibit spin compensation.

Calculations of lattice thermal conductivities have been performed, using the self-consistent phonon approximation to treat the zero-point motion.

Resonant interference between one- and two-phonon states has been observed in BaTi${\mathrm{O}}_3$, and has been shown to obey the quantum mechanical formalism developed by Fano for Auger processes. By selecting different components of the differential polarizability tensor and by changing the propagation direction, the degree of interference could be varied over a wide range. The linewidth and line-profile parameters were determined for several different crystal orientations.