We investigate molecular-orbital (MO) x-ray transitions resulting from collisions between 7-95-MeV sulfur ions and various thin, solid targets. MO radiation profiles beyond the united-atom limit are measured over several orders of magnitude in intensity, and absolute contributions of spontaneous and induced MO x rays are identified. We discuss formulations of MO theories which are in excellent agreement with our experimental spectral shapes and cross sections.

We have measured the Rayleigh intensity and linewidth in cholesteryl oleyl carbonate continuously through the cholesteric-isotropic phase transition. Above the phase transition the intensity data do not agree with the theory of de Gennes; we also do not observe the instability of the isotropic phase predicted by de Gennes. At the phase transition we observe two exponentials simultaneously which we associate with order-parameter and director fluctuations.

The interaction of a pinched relativistic electron beam with a solid target is calculated by use of the Monte Carlo method for energy deposition and two-dimensional particle-in-cell (PIC) hydrodynamics to take into account the full effect of target expansion. Bremsstrahlung emission is also evaluated through the use of the Monte Carlo method. Self-magnetic-field effects are neglected. It is found that target expansion can considerably reduce the efficiency of energy deposition in the focal region.

An experimental study of irradiation of spherical targets by single relativistic electron beams has been conducted to determine deposition symmetry. A 700-keV, 300-kA, 100-nsec beam was used with diagnostics consisting of x-ray pinhole photography, flash radiography, and evaluation of anode-backing-plate damage. The degree of symmetry was typically much better than 2:1 over the target surface, indicating that single-beam irradiation could be an acceptable approach to pellet fusion.

The mechanism of the high-frequency driven ion-cyclotron instability is investigated and shown, for a $Q$-machine plasma column with symmetric external excitation, to correspond to a three-wave resonant process in which an electron-plasma wave decays into an electrostatic ion-cyclotron wave and an oppositely propagating electron-plasma wave, all waves being in their lowest-order mode.

Two-dimensional numerical-simulation techniques have been used to study fluid instability in laser-fusion pellets. Comparisons with analytic solutions in nonablating test cases show good agreement. Isentropic ablative accelerations exhibit growth rates 50%-100% of Rayleigh-Taylor values, while nonisentropic cases show suppressed growth. Design optimization has led to an impulsively accelerated, low-aspect-ratio shell which operates successfully with a surface perturbation of a few tens of angstroms.

We report the first magnetic data for an expanded liquid metal: the Knight shift in liquid Hg from the normal liquid density to less than 8 g/${\mathrm{cm}}^3$ at 1730 K and 1411 bar. An abrupt metal-nonmetal transition between 9 and 8 g/${\mathrm{cm}}^3$ is preceded by ranges of roughly linearly decreasing shift ($11\lesssim \rho \lesssim 13.6$ g/${\mathrm{cm}}^3$) and constant shift ($9\lesssim \rho \lesssim 11$ g/${\mathrm{cm}}^3$). The latter behavior fails to support current theories developed to explain electronic transport properties.

From available quadrupole coupling constants in noncubic metals, measured with the sign, we have extracted in each case the component $e{q}^{\prime }$ commonly attributed to specific conduction-electron field gradients. These data reveal for the first time a systematic and universal dependence of $e{q}^{\prime }$ on the lattice gradient as well as the Sternheimer antishielding factor $1-{\gamma }_{\infty }$. This is unexpected from the point of view of current theoretical models of the electric field gradients in metals.

Electron-energy-loss spectra of epitaxial Al foils of {110} orientation show previously unobserved structures between 1.5 and 10 eV for the momentum transfer $\overrightarrow{\mathrm{k}}$ in directions $〈100〉$, $〈110〉$, and $〈111〉$. For $\overrightarrow{\mathrm{k}}\parallel 〈100〉$, this structure may be consistently interpreted within the essential features of the nearly-free-electron-band structure. Interband transitions show a marked influence on the plasmon dispersion for small $k$; only for $k>\mathrm{}0.75\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$ may it be discussed within the jellium model.

A simple picture based on colored quarks and gluons yields ${\alpha }_{\rho }\mathrm{}\left(0\right)=\frac{1}{2}$, ${\alpha }_{\Delta }\mathrm{}\left(0\right)=0\mathrm{}$, and ${\alpha }_{\mathrm{P}}\mathrm{}\left(0\right)=1\mathrm{}$, and explains various features of Pomeron exchange.

Strong photoionization spectra have been observed in molecular iodine following laser excitation in the near ultraviolet. The dependence upon laser power, and the structure of the spectra are consistent with three-photon ionization with resonance in an intermediate state excited by two photons.

A polyisotopic sodium beam of ${}_{}{}^{21-25}{}_{}{}^{}\mathrm{Na}$, produced by spallation of Al, was illuminated with a tunable cw dye laser. The atomic beam, analyzed by a six-pole magnet is then ionized and detected by use of a mass spectrometer. The results are as follows: isotopic shifts relative to ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$=-53.5 mK, ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$=-25.3 mK, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$=+23.1 mK, ${}_{}{}^{25}{}_{}{}^{}\mathrm{Na}$=+44.6 mK; ${\mu }_I\left({}_{}{}^{25}{}_{}{}^{}\mathrm{Na}\right)=+3.685\mathrm{}\left(22\right)\mathrm{}{\mu }_N$; $b$ factor in the $P_{\frac{3}{2}}$ state of ${}_{}{}^{25}{}_{}{}^{}\mathrm{Na}$=-16(8) MHz.

The proton spin lattice relaxation time was measured as a function of temperature over an extended nematic range for $p$-methoxybenzylidene aminophenylacetate and $p$-azoxydianisole by supercooling. The results show that the relaxation rate varies exponentially with reciprocal temperature in a manner similar to that in $p$-methoxybenzylidene butylaniline and ethoxybenzylidene butylaniline. The results are interpreted in terms of the Doane, Tarr, and Nickerson model of relaxation in nematic mesophases.

A damping-growth transition for ion-acoustic waves propagating in a nonuniform plasma ($e$-folding length for the density $l_n$) is observed at a wavelength $\lambda \sim 2\pi l_n$. This result supports calculations performed in connection with the problem of heating of the solar corona by ion-acoustic waves generated in the solar photosphere.

The $\frac{1}{f}$ noise spectra of current-biased tin films on glass substrates at the superconducting transition were in quantitative agreement with the semiempirical formula of Clarke and Voss. Tin films with an aluminum underlay to reduce the thermal boundary resistance between film and substrate had spectra that were flat at low frequencies. Spatial correlation of the noise was observed in both types of samples.

Low-temperature specific-heat measurements of amorphous silica and polymethyl methacrylate have been performed on a ${10}^{-4\mathrm{}}$-sec time scale using a novel heat-pulse technique. The data disagree with a recent theoretical prediction of Phillips and of Anderson et al. This prediction is based on the assumption that tunneling states are the origin of both the linear temperature dependence of the specific heat and the $T^2$ temperature dependence of the thermal conductivity characteristic of all glasses at low temperatures.

A first-principles linear combination of atomic orbitals calculation of the electronic energy structure of amorphous silicon based on Henderson's 61-atom quasiperiodic lattice model has been performed. The potential is constructed by a superposition of atomic potentials with interactions between all atoms included. The lattice summation of multicenter integrals, evaluated by the Gaussian technique, is performed to convergence. Results on energy levels and density of states are presented and compared with experiments.

Quantitative experimental results for the logarithmic corrections to the Landau specific heat are reported for the dipolar Ising ferromagnet LiTb${\mathrm{F}}_4$ near its Curie temperature $T_c=2.885\mathrm{}$ K. The power of the leading logarithmic term is found to be 0.34±0.03, and the corresponding amplitude ratio is 0.24±0.01. These results are in agreement with the predicted values of $\frac{1}{3}$ and ¼, respectively.

The temperature dependence of the magnetic-excitation spectrum in a singlet-doublet system is calculated by use of a generalized Vaks-Larkin-Pikin diagram technique. The first-order terms in the high-density expansion representing scattering on single-site fluctuations give an almost complete description of the line shapes in double-hcp praseodymium at any temperature.

We have enlarged the theory of the coercive force to include the wave nature of the ferromagnetic domain walls. Specifically, we obtain an explicit equation for the magnetic field required to move a 180° ferromagnetic domain wall across a planar defect such as a grain boundary. Using this expression, we have been able to classify successfully both low- and high-coercive-force materials.