Fano's theory of configuration interaction has been extended to Jahn-Teller systems. Homogeneous broadening and shift of the zero-phonon lines are directly connected with interlevel spin-orbit interaction and with the density of states of the interacting continuum. Application to MgO: ${\mathrm{V}}^{2+}$ and ${\mathrm{Al}}_2$${\mathrm{O}}_3$: ${\mathrm{Cr}}^{3+}$ gives excellent agreement between theory and experiment.

Microwave radiation (0.1 to 12 GHz) was propagated in a microstrip transmission line formed by a superconducting Al film on a Ba${\mathrm{F}}_2$ substrate. Cross strips formed Al-Al oxide-Al tunnel junctions that were used to study the effect of microwaves on the superconducting properties of the Al films. Large increases in the energy gap and transition temperature were observed for frequencies near 3.7 GHz. The enhancements were negligible below 1 GHz. Anomalous behavior of the features in the tunneling characteristics was observed above 5 GHz.

Applying the time-differential perturbed angular distribution method on three long-lived nuclear isomers in Ce isotopes, we present microscopic observations of the $4f^1$ state and its interactions with conduction electrons of extremely dilute Ce ions in solid and liquid metals in the temperature range 77 to 950 K.

The finite-temperature magnetic properties of the (100) surface of vanadium have been studied by means of spin-fluctuation theory. It is found that the surface contribution to the magnetic susceptibility exhibits strong temperature dependence having its origin in the appearance of large localized moments at the surface. These moments show antiferromagnetic interactions. These findings are in agreement with recent experiments.

Structure in the induced torque rotation pattern of potassium, observed for magnetic fields above 5 T and at a sample temperature of 1.4 K, gives evidence of open orbits in potassium. The presence of open orbits is expected from the charge-density-wave model of potassium but the directions of induced-torque peaks are not explained satisfactorily by the model.

Band representations of space groups are defined and they are used for the symmetry specification of bands in solids. While the symmetry of atomic orbitals is specified around a single center, the band symmetry of a solid is defined with respect to a whole lattice of centers.

Peculiar rodlike diffuse critical scattering above the type-I antiferromagnetic (AF/D) phase transition has been observed in the actinide compound UAs and demonstrates that the transition is in the vicinity of a Lifshitz point. A mean-field theory is proposed based on an anisotropic Hamiltonian and provides a reasonable description of the results.

The electron-core-hole interaction is studied via energy derivative reflectance spectra of 20-eV transitions from Ga $3d$ core levels to lower conduction-band final states in $\mathrm{Ga}{\mathrm{As}}_{1-x}{\mathrm{P}}_x$ alloys. A two-level anticrossing behavior of line shapes and threshold energies as the relative positions of the $L$ and $X$ minima invert yields a previously unanticipated $L-X$ mixing energy $\left|V_{\mathrm{LX}}\right|\sim 50$ meV.

By measuring the penetration depth and the critical current of three-dimensional assemblies of weakly coupled superconducting grains as a function of temperature, two critical exponents, $\beta$ and ${\nu }^{\prime }$, were determined characterizing the transition to coherence of the system. As in calculations on disordered systems, strict universality does not hold, but the exponents are shown to be compatible with the hypothesis of weak universality.

The results of a tunneling experiment in thin films of amorphous Mo and Nb stabilized with ${\mathrm{N}}_2$ are presented. The data were analyzed by several methods to obtain the Eliashberg function, ${\alpha }^{2}F\left(\omega \right)$. The resulting spectra are qualitatively different from ${\alpha }^{2}F\left(\omega \right)$ of amorphous simple metals, and in good agreement with computer model simulation of Rehr and Alben of the phonon spectrum of amorphous transition metals.

The Raychaudhuri equation is used to analyze the effect of the Hawking radiation back reaction upon a black-hole event horizon. It is found that if the effective stress-energy tensor of the Hawking radiation has negative energy density as expected, then an evaporating black hole initially a solar mass in size must disappear in less than a second. This implies that either the evaporation process, if it occurs at all, must be quite different from what is commonly supposed, or else black-hole event horizons—and hence black holes—do not exist.

General techniques are introduced to expose new $\mathrm{CP}$-nonconserving effects in cascade decays of $B$ mesons. These effects are computed in the Kobayashi-Maskawa model. The $\mathrm{CP}$ asymmetries so obtained range from 2% to 20% if the parameters are in the favorable range $s_3<s_2\lesssim 0.1$. Effects of this size should be observable in upcoming experiments.

In a sample of ∼15000 charged current $\nu +d$ interactions from an exposure of the Fermilab 15-ft bubble chamber to a high-energy, wide-band neutrino beam, the production of the ${{\Lambda }_c}^{+}$ charmed baryon decaying into $\Lambda {\pi }^{+}$ and $K^{0}p$ is observed. The measured mass value is 2.275±0.010 GeV. The products of the production rate and the branching ratio for these channels are (1.8±0.9)×${10}^{-3\mathrm{}}$ and (3.5±2.0)×${10}^{-3\mathrm{}}$, respectively.

The Crystal Ball detector at SPEAR has been used to investigate the decays ${\psi }^{\prime }\to \eta \frac{J}{\psi }$ and ${\psi }^{\prime }\to {\pi }^0\frac{J}{\psi }$ resulting from production of 776000 ${\psi }^{\prime }$. Our measurement for the branching ratio of the $\eta$ mode is (2.18 ± 0.14 ± 0.35)%, where the first error results from statistics and acceptance uncertainties, and the second error is systematic; this is almost a factor of 2 smaller than found in early experiments. For the isospin-nonconserving ${\pi }^0$ mode, a branching ratio (0.09 ± 0.02 ± 0.01)% is obtained.

A massive Dirac neutrino has a magnetic moment, which causes its spin to precess in a magnetic field. This reduces the effective weak cross sections for relativistic neutrinos. An estimate on the basis of phenomenological considerations as well as the standard electroweak theory indicates that massive neutrinos from supernovae and neutron stars may contain significant mixtures of negative- and positive-helicity states.

Correlations of two ${\pi }^0$ mesons with transverse momenta $p_T$ up to 13 GeV/c have been measured with large azimuthal acceptance. Results for cross sections, $p_{\mathrm{out}}$, and $z$ distributions are compared in detail with models based on two-constituent scattering and fragmentation. The width of the constituent transverse-momentum Gaussian distribution would have to be doubled to match that from experiments with $p_T$ below 5 GeV/c. A more likely explanation is the presence of processes with more than two constituents in the final state.

The ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}F_3^{}{}_{}{}^{}$ $N-N$ amplitudes are studied in a unitary dynamical model. Parameterfree long- and medium-range forces are given by multiple pion exchange, allowing coupling to the $\mathrm{NN}\pi$ channel. Short-range forces are mainly given by $\rho$ and $\omega$ exchange, parametrized to fit known low-energy phase shifts for $J>~2$. Resulting Argand diagrams at medium energies show counter-clockwise loops, but far less dramatic than in the Hoshizaki phase-shift analysis. However, the results are similar to recent Arndt phase shifts.

A classical, static non-Abelian gauge-field configuration with singularities along a line is exhibited and its effect on cross sections for massless fermion creation computed. It is shown that, while the effect of such a configuration on inclusive processes is negligible at high energy, its contribution to certain differential processes can be substantial, even to the point of dominating over the nominally leading, perturbative results.

It is shown that it is possible to obtain the neutral-current weak interaction as the third component of the SU(2) group without electroweak unification, provided that fundamental doublets contain in general a mixture of left-handed and right-handed fields. The main experimental consequencé is the relation ${m_W}_3\simeq \sqrt{2}{m}_W$, with the further posibility that $m_W$ could be lower than that predicted by the standard model.

A broad bump in $t$ spectra from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-induced nuclear reactions has been observed. Energy and target-mass dependences have been investigated. Possible reaction mechanisms are discussed.