The isotope shifts of ${}_{}{}^{188}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$, and ${}_{}{}^{184}{}_{}{}^{}\mathrm{Hg}$ in the 2537-Å line have been measured by use of tunable dye laser at the on-line mass separator ISOLDE at CERN. The results are $\delta \nu ({}_{}{}^{188}{}_{}{}^{}\mathrm{Hg}-{}_{}{}^{204}{}_{}{}^{}\mathrm{Hg})=35.8\mathrm{}\left(2\right)\mathrm{}$ GHz; $\delta \nu ({}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}-{}_{}{}^{204}{}_{}{}^{}\mathrm{Hg})=39.4\mathrm{}\left(2\right)\mathrm{}$ GHz; and $\delta \nu ({}_{}{}^{184}{}_{}{}^{}\mathrm{Hg}-{}_{}{}^{204}{}_{}{}^{}\mathrm{Hg})=43.1\mathrm{}\left(2\right)\mathrm{}$ GHz. These data combined with those obtained by $\beta$-radiation-detected optical pumping ($\beta$-RADOP) on the odd Hg isotopes yield a huge odd-even staggering for ${}_{}{}^{185}{}_{}{}^{}\mathrm{Hg}$ of $\gamma =\frac{\left(2\mathrm{}\delta {\nu }^{\frac{185}{184}}\right)}{\delta {\nu }^{\frac{186}{184}}}=13\mathrm{}\left(1\right)\mathrm{}$ which has to be interpreted as nuclear shape staggering.

The $4s-4p$ resonance transitions in the copperlike and zinclike ions from Rb to Mo have been observed by means of a low-inductance open spark and a 10.7-m grazing-incidence spectrograph. Lines belonging to highly charged ions could be distinguished by their abnormally large widths. The observations confirm the identification of the resonance lines of Mo xiii and Mo xiv in the Princeton University $\mathrm{ST}$ tokamak by Hinnov, Johnson, Meservey, and Dimock.

This Letter report the application of the Stark-switching technique to study the two-photon coherent precession effect. Using this technique, I have made the first time-do-main measurement of the collision-induced dephasing time in a two-photon transition in N${\mathrm{H}}_3$, and the result is compared with pressure-broadening measurements in the frequency domain.

We report the computer-generated damping rates of shocked acoustic pulses in a perfect fluid for the entire range of velocity discontinuity $0<~\Delta v<~c$. We obtain the significant result that the damping rate, instead of increasing monotonically with $\Delta v$, decreases asymptotically and vanishes as $\Delta v\to c$. Hence the conventional weak-shock decay law fails completely in the limit of strong relativistic shocks.

Fast shock heating in a toroidal belt pinch produces a highly elongated, weakly compressed high-$\beta$ plasma with electron and ion temperatures in the keV range. Electron heating is attributed to ion-sound turbulence. The effective drift velocity is increased above instability threshold by a distortion of the electron distribution related to strong density and temperature gradients. Quenching of the instability is related to ion-tail formation. Reflection of ions by the piston, however, is mainly responsible for ion heating and increases with increasing initial density.

A model for the University of Texas turbulent torus is described. The prediction of the model shows a strong skin effect, and is in agreement with the experimental data if one saturates the Buneman instability by using the electron-trapping condition and the ionsound instability by using the anomalous collision frequency ${\nu }^A\simeq {10}^{-5\mathrm{}}\left(\frac{T_e}{T_i}\right)\left(\frac{u}{v_e}\right){\omega }_{\mathrm{pe}}$, which correlates with ion tail formation. An interpretation of the laser-scattering temperature measurements is proposed.

The physical mechanism of the Alfvén ion-cyclotron instability due to ion-temperature anisotropy in a high-$\beta$ plasma is explored. We have observed evidence for the proposed mechanism in runs on a magnetostatic particle simulation code. Saturation and stabilization of the instability are discussed on the basis of the present mechanism.

A stationary spectrum in the frequency range much below the ion cyclotron frequency is obtained for a strongly turbulent nonuniform plasma. The $\omega$-integrated $k$ spectrum is given by $k^{1.8}{(1+k^2)}^{-2.2\mathrm{}}$, while the width of the frequency spectrum is proportional to $k^3{(1+k^2)}^{-1\mathrm{}}$, where $k$ is normalized by $\frac{c_s}{{\omega }_{\mathrm{ci}}}$. The result compares well with the recently observed spectrum in the ATC tokamak.

High-resolution electron-energy-loss spectroscopy is applied to detection of surface vibrations induced by adsorption of hydrogen on clean W(001). The two $\beta$ states are resolved and a bending mode of the ${\beta }_2$ state is detected. Results of experiments with ${\mathrm{D}}_2$ and HD compared with those of the calculated vibrational modes of their possible molecular configurations on W(001) constitute a decisive and conclusive proof of the atomic nature of these adsorbed species on W(001) for the whole range of coverage.

We have derived a microscopic Hamiltonian that takes into account rotational-translational coupling in molecular crystals. This coupling leads to an effective orientational interaction among nonspherical molecules. It is responsible for an anomalous behavior of the elastic constants and of the transverse-acoustic phonons. The temperature behavior of $c_{44}$ and $c_{11}$ in KCN above the 168-K phase transition is explained.

Inelastic and elastic neutron scattering have been used to study the dynamics and structure of butane (${\mathrm{C}}_4$${\mathrm{H}}_{10}$) adsorbed on a graphitized carbon powder at 77 K. In addition to the intramolecular vibrations found in the bulk solid, new surface vibratory modes are observed. A simple model which fits the principal features of the monolayer excitation spectrum suggests an orientation of the adsorbed butane molecule and the location and strength of the bonds to the substrate.

Measurements on the antiferromagnet ${\mathrm{Fe}}_x\mathrm{O}$ demonstrate that threshold photoelectric currents plotted vs temperature yield the spin correlation function of a thin sheet at the surface. The data support an interpretation based on a magnetic final-state effect. Similar phenomena are expected to occur in many magnetic materials.

We demonstrate the efficiency of scattering of reflected light from shear bulk acoustic phonons, acoustoelectrically amplified in the frequency range of $0.2<~f<~2$ GHz in GaAs and CdS. Bulk-phonon-induced surface ripples, as opposed to fluctuations in the dielectric constant, are shown by several experiments to provide the dominant scattering mechanism.

Serious doubt is cast on Allen's claim that the anomalous high-temperature electrical resistivity of Nb cannot be accounted for within the framework of the Boltzmann equation.

The behavior of a superconducting A1 film under conditions of large nonequilibrium injection of quasiparticles is studied by means of a tunnel generator and detector. At a critical injection density, $n_c$, a second energy gap develops in the superconductor. The relevance to recent theories of nonequilibrium superconductivity is discussed.

We report measurements of the electrical conductivity, $\sigma$, of thin amorphous films of hydrogen tungsten bronze, ${\mathrm{H}}_x\mathrm{W}{\mathrm{O}}_3$, as a function of temperature and hydrogen/tungsten ratio, $x$. For $x\lesssim 0.3$ the temperature dependence of $\sigma$ can be explained by the variable-range hopping model. At $x=0.32\mathrm{}$ an insulator-to-metal transition occurs with a minimum metallic conductance of about 5.1 × ${10}^{-5\mathrm{}}$ ${\mathrm{\Omega }}^{-1\mathrm{}}$.

The dynamical stability of the current in a superconducting filament against small fluctuations of the complex order parameter and the electric potential is studied using equations based on time-dependent self-consistent mean-field theory. In the low-frequency, long-wavelength limit near the transition temperature, simple calculations are performed which predict slowing modes associated with the tendency toward resistive behavior.

Backward-wave phonon echoes (polarization echoes), heretofore only observed in piezoelectric crystals, were generated in several different glasses. Echo amplitudes were found to be proportional to the number of unassociated hydroxyl ions in the samples. It is proposed that O${\mathrm{H}}^{-}$ ions in glass form a distribution of inhomogeneously broadened resonances, sensitive to both ultrasonics and electromagnetic fields. Effect of this conjecture on other measurements in glasses are discussed, as are various measured properties of the echoes.

To reduce the discrepancies in the crystal-field analyses of the electronic configurations $4f^N$ of lanthanide ions, it is argued that each component ${\left({C_q}^{\mathrm{}\left(k\right)\mathrm{}}\right)}_i$ of the single-electron tensor $C^{\mathrm{}\left(k\right)\mathrm{}}$ for electron $i$ occurring in the conventional crystal-field Hamiltonian should be augmented to $c_k\left(\overrightarrow{\mathrm{s}}·{\overrightarrow{\mathrm{s}}}_i\right){\left({C_q}^{\mathrm{}\left(k\right)\mathrm{}}\right)}_i$. Parameters $c_k$ of the order of - 0.1 lead to significant improvements in the fit with a wide variety of experimental data.

Single- and double-pion inclusive spectra are presented for 100-GeV/c $\overline{p}p$ interactions and compared with related $\mathrm{pp}$ data. Double-fragmentation distributions are shown to be understood within a Mueller-Regge framework as a product of single-fragmentation distributions. Consideration of $\mathrm{pp}$ and $\overline{p}p-pp$ distributions shows factorization to hold in Pomeron and in Reggeon exchanges independently.