We have observed the elastic neutral-current reaction ${\nu }_{\mu }+p\to {\nu }_{\mu }+p$ and compared it to the quasielastic reaction ${\nu }_{\mu }+n\to {\mu }^{-}+p$. We have measured the ratio of the two reactions to be 0.23 ± 0.09.

Using a sample of 4994 neutrino events and 2408 antineutrino events we have measured the ratio of antineutrino to neutrino charged-current cross sections up to 100 GeV. Neutrino flux-independent and flux-dependent measurements were carried out with good agreement between the two methods. Below 30 GeV the ratio was found to be 0.38 ± 0.06. The cross-section ratio shows a significant departure from this value above 50 GeV.

The sign of $P_3=M_{02}{M}_{{22}^{\prime }}{M}_{{02}^{\prime }}$ [$M_{\mathrm{rs}}=-〈\mathcal{r}\parallel M\left(E2\mathrm{}\right)\mathrm{}\parallel s〉$] has been determined by observing interference between one-step and two-step amplitudes for $\alpha$-particle excitation of the second $2^{+}$ states of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}$ and ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$. The sign of $P_3$ predicted by Kumar and Baranger is found to be correct for ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ but incorrect for ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}$.

The spin alignment of excited states which decay in flight by $\gamma$ emission can be determined by measuring the line shape of the corresponding peak in the energy spectrum of the outgoing particle. The linewidth is broadened by the $\gamma$ recoil and the shape is characteristic for different $m$ substates.

Electron energy spectra obtained from the ${\mathrm{He}}^{+}$-He collision system at 1400-eV impact energy and at a laboratory emission angle of 180° show pronounced oscillatory structure. By comparison with calculated spectra using a simple potential-curve model, we show that the observed structure is due to an interference between the electron-emission amplitudes of different coherently excited autoionizing states.

We present the first direct observation of nucleus-nucleus bremsstrahlung from heavyion collisions, and demonstrate the characteristic forward-backward emission asymmetry predicted for interfering dipole and quadrupole emission components. These studies indicate that both the intensity and angular distribution of nucleus-nucleus bremsstrahlung constitute important considerations in the quasimolecular spectroscopy of heavy collision systems.

By applying oscillating charges to a small probe in a magnetized plasma, we observed the low-frequency resonance cone below the ion-cyclotron frequency. The observed cones were in quantitative accord with theoretical results which include the effect of the ion temperature. The measurement of the low-frequency cones may be useful for determining the ion temperature.

The propagation of ion-acoustic waves in two-ion plasmas is investigated both experimentally and theoretically when the ratio of electron to ion temperature is 10 to 15. Although a single mode is observed in an argon-neon plasma, two modes are detected in an argon-helium plasma.

Essentially exact numerical solutions of the self-consistent atom-jellium model are used to show how the chemical concepts of electronegativity, shell-filling, and covalent or ionic bonding manifest themselves in the microscopic redistributions of charge and state density which accompany chemisorption. Realistic results are provided for chemisorbed Li, Cl, and Si, illustrating the three basic types of bonding—cationic, anionic, and covalent.

The frequency-dependent conductivity $\sigma \left(\omega \right)$ of a two-dimensional interacting electron gas in the presence of a random array of scattering centers and a dc magnetic field is studied. Electron-electron interaction effects enter $\sigma \left(\omega \right)$ through the holomorphic memory function $M\left(\omega \right)$ whose imaginary part is the inverse of the frequency-dependent relaxation time $\tau \left(\omega \right)$. A qualitative explanation of some of the perplexing results observed in infrared cyclotron resonance, including how electron-electron interactions affect both the fundamental and harmonics, is given.

I have calculated the electronic spectra of CO adsorbed onto Ni(001) in the $c(2\mathrm{}\times 2)$ structure. The $4\sigma$ band is found 10.8 eV below $E_{\mathrm{F}}$. The $1\pi$ and $5\sigma$ bands overlap to form one peak at - 7.9 eV below $E_{\mathrm{F}}$. This two-peak structure agrees with photoemission measurements. The results indicate that the chemisorbed CO molecular states are sufficiently extended so that dynamic final-state relaxation effects are negligible, and energy-level shifts are due to chemical bonding alone. Similar results are obtained for ${\mathrm{C}}_2$${\mathrm{H}}_4$ and ${\mathrm{C}}_2$${\mathrm{H}}_2$.

The methods of statistical mechanics are used to evaluate sums of many-vertex Feynman graphs in a simple quantum-field-theory model.

We rigorously prove that in three or more dimensions, the nearest-neighbor, simple-cubic, ferromagnetic, quantum Heisenberg model of spin $S(=\frac{1}{2}, 1, \dots )$ has a phase transition at nonzero temperature.

Recent measurements of ($p, {\pi }^{+}$) reactions near threshold allow us to restrict substantially the possible forms of the empirical nonrelativistic $\pi \mathrm{NN}$ vertex.

A search has been made for photoproduced bosons or leptons of mass between 1.2 and 3.5 GeV that decay into either an electron-positron pair, two photons, or an electron and a photon. Within the sensitivity of the experiment no evidence for any new narrow resonance was found. An upper limit is given for the cross section per nucleon times the branching ratio.

Counter-telescope and recoil-coincidence techniques were used to observe the reaction ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{22}{}_{}{}^{}\mathrm{O}$ at 100 MeV. These data indicate a mass excess for ${}_{}{}^{22}{}_{}{}^{}\mathrm{O}$ of 9.48±0.10 MeV, which differs by ∼2.0 MeV from the previous value, but is in excellent agreement with several theoretical predictions.

A new technique exploiting proton-x-ray coincidences has been used to measure ${10}^{-16\mathrm{}}$-sec lifetimes of proton-unstable levels in ${}_{}{}^{69}{}_{}{}^{}\mathrm{As}$ produced in the electron-capture decay of ${}_{}{}^{69}{}_{}{}^{}\mathrm{Se}$. The results are compared with statistical-model calculations.

An intracavity crossed laser-beam, molecular-jet-beam system has been developed for studying the properties of expanding jet beams by means of light scattering. Raman scattering has been used to measure the local rotational temperature and absolute density of monomers in a jet beam of C${\mathrm{O}}_2$ as a function of axial distance from the nozzle. A well-defined rotational temperature has been observed. This temperature drops rapidly for distances of a few nozzle diameters in agreement with isentropic theory and thereafter remains roughly constant.

A three-dimensional, nonlinear, numerical simulation is described in which saw-tooth oscillations occur as a result of a hydromagnetic relaxation instability. The time evolution of the magnetic topology demonstrates the essential validity of the model suggested by Kadomtsev to explain the saw-tooth oscillations observed in tokamak experiments.

Warm plasma has been injected along field lines into a quasi-steady-state magnetic mirror in the $2X\mathrm{IIB}$ experiment. This has provided a suitable target plasma for density buildup and heating with neutral-beam injection. With the injection of 310 A equivalent of 14-keV deuterium atoms, the density exponentiated to 3.7 × ${10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$, the average ion energy increased to 12 keV, and the $\beta$ reached 0.4. A rate equation describing the density buildup is given.