We report the observation of inelastic interactions induced by high-energy neutrinos and antineutrinos in which no muon is observed in the final state. A possible, but by no means unique, interpretation of this effect is the existence of a neutral weak current.

We employed a graphite mosaic crystal spectrometer to study the $K$ x rays from thin targets of titanium and manganese following bromine-ion bombardment. From the shifts and intensity ratio of the $K\alpha$ and $K\beta$ x rays we determine the $L$- and $M$-shell vacancies at $K$ x-ray emission. By estimating the effects of vacancy rearrangement before $K$ x-ray emission, we conclude that in the initial collision more $L$ vacancies are created in titanium than in manganese.

We report the determination of the hyperfine, $\rho$-doubling and rotational constants of the CN molecule, by observation of its $N=1\mathrm{}\to 0$ line emission from an interstellar molecule cloud. The $N=1\mathrm{}\to 0$ multiplet has seven allowed transitions, all of which were measured to an accuracy of 0.5 MHz or better. This astronomical measurement is the first sucessful attempt at determining the CN hyperfine structure in the free molecule, since the appropriate transitions have yet to be observed in the laboratory.

A quantum-electrodynamic theory of spontaneous emission in the presence of a dielectric has been worked out, and formulas are presented for the change in the lifetime and the Lamb shift of a two-level atom, as a result of the presence of a dielectric. Curves are given for the behavior of the damping as a function of the distance of the atom from the interface. The frequency shift for the case of a conductor is also evaluated.

"Surface sound" has been observed for the first time, in ${\mathrm{He}}^3$ adsorbed on the free surface of liquid ${\mathrm{He}}^4$. Measurements of the surface-sound velocity and surface tension are used to obtain new values for the effective mass $M=(1.3\mathrm{}\pm 0.1)m_3$ and binding energy $\frac{{\epsilon }_0}{k_B}=2.28\mathrm{}\pm 0.03$ K of the adsorbed ${\mathrm{He}}^3$.

The attenuation of 2-GHz acoustic surface waves in a 300-Å aluminum film has been measured in the temperature region around the superconducting transition temperature. The simple BCS theory yields a gap parameter of 3.60. While microwave electromagnetic-attenuation measurements in the film indicate critical fluctuation effects near $T_c$, there appear to be no such fluctuation effects in the ultrasonic-attenuation data of this short-mean-free-path Al film.

We have found what we believe to be a universal characteristic of layered superconductors: A positive curvature of the $H_{c2}$-versus-$T_c$ boundary. The origins of the effect are believed to be associated with strong anisotropies of the Fermi surface and electronphonon interaction.

Using an exactly soluble model, the decay rate of a current-carrying state of one-dimensional fermions is calculated in the presence of random scatterers at finite temperature and the dc conductivity thereby inferred. For interacting fermions it is modified by a factor ${(\frac{T}{T}+\theta )}^g$, where $g$ is a positive (negative) coupling constant for repulsive (attractive) two-body forces. While the conductivity could be greatly enhanced for $g<\mathrm{}0\mathrm{}$ and $T\ll \theta$, one-dimensional superconductivity appears ruled out at any finite temperature.

The peak structures observed in the magnetoacoustic attenuation in $p$-Ge are ascribed to the resonance absorption by acceptor holes, which is caused by the sublevel crossings due to the second-order Zeeman effect. The anisotropy with respect to the direction of a magnetic field is explained. The behavior of the magnetothermal conductivity, regarded as evidence for the Jahn-Teller effect, can also be explained by our model.

The electronic energy band structure of $2H-\mathrm{Nb}{\mathrm{Se}}_2$ is calculated using the empirical pseudopotential method. The results are compared with other calculations and with experimental data. Charge densities for the completely filled valence bands and the partially filled conduction bands are calculated using a set of special $\overrightarrow{\mathrm{k}}$ points in the Brillouin zone. The relations between the calculated charge densities and the various bonding models are discussed.

Neutron scattering has been used to investigate the structure of nitrogen adsorbed on Grafoil. At 78°K, the diffraction patterns at the lowest and highest coverages studied are characteristic of systems with short-range but no long-range order. At intermediate coverages the diffraction patterns indicate formation of a two-dimensional triangular lattice in registry with the substrate. At low temperatures and high coverages a more compressed triangular lattice formed.

The two-photon absorption spectrum due to excitonic molecules is measured in CuCl at 77 and 4.2°K. We measured values of the two-photon transition cross section of the order of ${10}^{-44\mathrm{}}$ ${\mathrm{cm}}^4$ sec and estimated a peak value of ${10}^{-42\mathrm{}}$. The binding energy of the molecule is found to be 255 ${\mathrm{cm}}^{-1\mathrm{}}$.

Exact renormalization-group recursion relations are studied for a spin-1 Ising model in one dimension. In this model, critical lines are marked by a double degeneracy of the largest eigenvalue of the transfer matrix, and the tricritical point by a triple degeneracy. This is directly related to the tricritical fixed point being more unstable than the critical fixed points.

Diagonalization of a Hamiltonian containing magnetic, elastic, and magnetoelastic contributions leads to mixed modes of magnetoelastic character. Linear combinations of creation operators appropriate to standing waves are formed, and boundary conditions require a node at the substrate-film interface, and an antinode at the free surface. Standing-wave modes can be excited with applied rf and dc fields perpendicular to each other in the plane of the film.

We observed "quasifission" events (or "incomplete fusion" events) in the bombardment of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ by 525-MeV ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ ions. By a simple method, the angular distribution of these events has been obtained. Its maximum value appears around 65° lab, i.e., ∼95° c.m. The integrated cross section for this reaction is 500 mb, more than $\frac{1}{2}$ of the total reaction cross section. No symmetric fission coming from a complete fusion nucleus has been observed, and it seems that the "quasifission" reaction occurs instead of complete fusion, as was previously observed at 500 MeV bombarding energy.

It is shown that nuclear matter is compressed during the encounter of heavy ions. If the relative velocity of the nuclei is larger than the velocity of first sound in nuclear matter (compression sound for isospin $T=0\mathrm{}$), nuclear shock waves occur. They lead to densities which are 3-5 times higher than the nuclear equilibrium density ${\rho }_0$, depending on the energy of the nuclei. The implications of this phenomenon are discussed.

We have used rf techniques and a fast hydrogen beam to observe in zero magnetic field the two-quantum transition ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}$ in the $n=3\mathrm{}$ state of atomic hydrogen. The possibility of using this and related transitions for a high-precision measurement of the fine-structure constant is discussed.

We present an experimental technique enabling a direct observation of the momentum transfer distribution generated by rotationally inelastic molecular collisions of ${\mathrm{CO}}_2$ with ${\mathrm{H}}_2$, He, ${\mathrm{CO}}_2$, and Kr. The observations indicate that the rotational transition results primarily from peripheral collisions which are effective in transferring angular momentum, but which communicate a relatively small linear momentum transfer. The mean change in the $z$ component of velocity is presented for ${\mathrm{CO}}_2$-${\mathrm{H}}_2$ collisions.

We have measured the fine-structure splitting of the $4d{}_{}{}^2{}_{}{}^{}D$ state of neutral sodium using high-resolution, cw, simultaneous two-photon excitation from the $3s{}_{}{}^2{}_{}{}^{}S$ ground state. Sodium atoms in an atomic beam were excited by a single-mode, cw, tunable dye laser, and the resonance was detected by monitoring the decay fluorescence from the excited state. The fine structure of the $4d{}_{}{}^2{}_{}{}^{}D$ state was well resolved and measured to be ${\Delta }_{\mathrm{fs}}=1025\mathrm{}\pm 6$ MHz.

Experiments on the $3S-5S$ two-photon transition in sodium give evidence that Doppler broadening is eliminated if the atom absorbs two photons propagating in opposite directions. The proof is given by the comparison of the two-photon absorption line shape in traveling and standing waves.