Energy analysis has been performed on 63-meV He atoms scattered from 135°K LiF(001) along the $〈010〉$ direction. The results suggest that single Rayleigh phonons dominate the interaction near specular scattering. Points on the dispersion curve are determined uniquely and suggest a limiting speed of sound of (4.2 ± 0.5) × ${10}^5$ cm/sec.

We report optical absorption measurements made on thick, highly pure crystals of ${\mathrm{Cu}}_2$O at 1.6 K. For the first time direct evidence is provided for a phonon-assisted paraexciton absorption edge. The relative strengths of phonon-assisted paraexciton and orthoexciton absorption edges are discussed.

We show that contribution of monopole loops to the functional integral in four-dimensional lattice (quantum electrodynamics) can be mapped on to scalar quantum electro-dynamics. The phase transition where the monopole loops become very long then corresponds to the onset of the Higgs-Kibble mechanism and confinement due to the dual Meissner effect.

We have measured the difference between the $\mathrm{pp}$ total cross sections for parallel and antiparallel longitudinal spin states at beam momenta of 1.0, 1.1, 1.30, 1.58, 1.71, 2.1, and 2.25 GeV/c in a transmission counter experiment. These results reveal new structure in the $p_{\mathrm{lab}}$ range of 1.0 to 2.5 GeV/c.

We have observed eleven events of the reaction ${\nu }_{\mu }{e}^{-}\to {\nu }_{\mu }{e}^{-}$ in a sample of 106 000 charged-current neutrino interactions in a heavy neon-hydrogen mixture in the 15-ft. bubble chamber at Fermilab. We obtain a cross section for this process of $\left[\right(1.8\mathrm{}\pm 0.8)\times {10}^{-42\mathrm{}} {\mathrm{cm}}^2/\mathrm{GeV}]E_{\nu }$. This result is in good agreement with the prediction of the Weinberg-Salam model with ${{sin}^2\theta }_W=0.2\mathrm{}$.

It is shown that a sizable transition magnetic moment between ${\nu }_{\mu }$ and a massive neutrino ${\nu }^{\prime }$ (of mass of approximately 100 MeV) leads to some detectable effects. These effects could be revealed significantly in ${\nu }_{{\mu }^{-}} \left({\overline{\nu }}_{{\mu }^{-}}\right)$ electron scattering, but would remain hidden in most other cases. It is also pointed out under what circumstances a large transition magnetic moment arises in gauge models.

We have performed a high-sensitivity search for massive long-lived particles produced at 2.5 mrad by 400-GeV/c protons on a beryllium target using time-of-flight, Cherenkov, and calorimetric techniques. A total of ${10}^{11}$ light particles (${\pi }^{-},K^{-},\overline{p}$) was sampled at 70 GeV/c. This experiment places a limit of 1.1×${10}^{-37\mathrm{}}$ ${\mathrm{cm}}^2$/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ · nucleon on the invariant cross section for the production of stable particles in the mass range of 4 to 10 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.

We have made a systematic search for direct $e^{+}$ and $e^{-}$ production in $p-p$ and $p$-Be collisions at 12 GeV/c incident proton momentum. Data were collected at c.m. angles of 20°, 35°, 63°, and 84°. We find no evidence for the previously reported rise in the ratio $\frac{e}{\pi }$ at low momentum transfer. The data are consistent with zero direct electron production from other than previously known sources.

It is shown that experiments on $\tau$ decay and multipion production in $e^{+}{e}^{-}$ colliding beam can be used to test the hypothesis of conserved vector current, and current algebra at large timelike momentum transfer $Q^2$, independently of the structure of the hadronic weak current coupled to $\tau$.

Excitation of the $K=2^{-}$ octupole band up to the ${14}^{-}$ member in the reaction ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}(p, 2n\gamma ){}_{}{}^{180}{}_{}{}^{}\mathrm{W}$ shows an odd-even energy staggering. This staggering can be interpreted in terms of different Coriolis-induced alignments of the rotational and octupole vibrational angular momenta for the odd- and even-spin members of the $K=2^{-}$ octupole band. There is no evidence that the $K=2^{-}$ octupole vibration decomposes into two-quasiparticle decoupled states even at the highest spins observed.

Apparent discrepancies in the amount of $E2\mathrm{}$ strength located in the giant resonance region of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ are resolved by a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\alpha , {\alpha }^{\prime }c)$ coincidence experiment at 104 MeV. The summed $E2\mathrm{}$ strengths in the dominant decay channels $c={\alpha }_0, {\alpha }_1$, and $p_0$ in the range $20<~E_x<~30$ MeV exhaust less than 15% of the energy-weighted sum rule. So far ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is the only investigated nucleus which does not exhibti a giant quadrupole resonance.

We have excited the 14-keV level of the ${\mathrm{Fe}}^{57}$ nucleus using synchrotron radiation, and observed the conversion electrons emitted in the decay of that state. We believe this to be the first observation of nuclear excitation via synchrotron-produced x rays.

Data have been obtained for the polarization analyzing power $A_y\left(\theta \right)$ in $\mathrm{pp}$ elastic scattering from near 30° to 90° (c.m.) at 643, 787, and 796 MeV. Relative uncertainties are typically ± 0.003 with an overall normalization uncertainty of $\left(\{+1\mathrm{}\}\{-0.5\mathrm{}\}\right)\%$. Data are not consistent with existing phase-shift analyses.

Pion-nucleus scattering is described by the excitation of bound nucleons into the $\Delta$ resonance leading to isobaric resonances of the whole nucleus. A few broad collective resonances of different multipolarity are shown to dominate elastic and inelastic $\pi$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ scattering. From the qualitatively good agreement with the data, we conclude that those giant isobaric resonances are a general feature of the nuclear excitation spectrum in the $\Delta (3, 3)$ energy range.

The possibility of observing neutron-rich isotopes in hard heavy-ion reactions is studied. The influence of target isospin correlations on participant and spectator mass and charge distributions is calculated. Calculated spectator distributions for a Pb target are compared to experiment.

Calculations for the $X{}_{}{}^2{}_{}{}^{}\Sigma$, $A{}_{}{}^2{}_{}{}^{}\Pi$, and $B{}_{}{}^2{}_{}{}^{}\Sigma$ states of the NaNe molecular system are reported. The electron-neon interaction is represented by a local potential together with an explicit orthogonality condition to the neon orbitals. The well depth and location are $D=7.8\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$ at ${\mathcal{r}}_m=10\mathrm{}$ a.u. for the $X{}_{}{}^2{}_{}{}^{}\Sigma$ state and $D=132\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$ at ${\mathcal{r}}_m=5\mathrm{}$ a.u. for the $A{}_{}{}^2{}_{}{}^{}\Pi$ state, in excellent agreement with the laser-spectroscopy results of Ahmad-Bitar et al.

Significant unexplained oscillator structure has been observed in the wings of the forward electron-loss peak from 1.6-3.9-MeV/amu ${\mathrm{O}}^{q+}$ and ${\mathrm{Si}}^{q+}$ ions traversing Ne and Ar gases. On the basis of the observed projectile $Z_1$, $q$, and velocity and target $Z_2$ dependencies, this structure appears likely to arise from interference of amplitudes describing alternative channels for populating projectile-centered continuum states, conceivably including channels involving simultaneous ejection of two or more electrons.

We report an observation of electric quadrupole transitions in a laboratory plasma. Two intense lines seen at 58.832 and 57.927 Å in the spectrum of the TFR tokamak are attributed to the $E2\mathrm{}$ transitions $3d^{10}-3\mathrm{}{d}^{9}4s(J=2\mathrm{})\mathrm{}$ of Mo xv. This classification is based on the agreement between experimental and computed values for wavelengths and intensities of these lines in the tokamak plasma. The influence of cascades on intensities is discussed.

A general virial theorem is proved without any assumption of special symmetries and used to calculate the threshold and time for direct collapse of a two-dimensional Langmuir wave packet. The analysis is shown to apply to "bump-on-tail" instabilities, when the "bump" is broad, low, and at high velocity. The example of the type-III solar radioburst problem is treated both numerically and analytically.

A well-defined internal-friction peak has been observed near 260 K in amorphous rf-sputtered films of ${\mathrm{Nb}}_3$Ge, studied at audio frequencies by a vibrating-reed technique. The characteristics of the peak are consistent with a stress-induced ordering mechanism involving a presently unidentified center which undergoes reorientation by an atomic jump with a sharply defined activation energy of 0.52 eV. The peak appears to be the first example of its type found in a metallic glass.