The Lamb shift $S$ in hydrogenlike argon ($Z=18\mathrm{}$) has been measured by a motional-electric-field-quenching time-of-flight experiment. We find $S=38.0\mathrm{}\pm 0.6$ THz where the error includes 1-standard-deviation statistical error of 0.35 THz and an estimated systematic error of 0.48 THz.

We have used the Doppler-tuned ion-beam, laser-spectroscopy method to measure the hyperfine intervals in the $2{}_{}{}^3{}_{}{}^{}S$ and $2{}_{}{}^3{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}$ states of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}_{}^{+}{}_{}{}^{}$. Our resolution was 10 times that of the best previous measurement. In contrast to the earlier experimental work we find excellent agreement between our measurements and the theoretical values.

Measurements of the relative photoionization cross sections of Rb in the presence of various strengths of external electric fields are reported. Systematic, field-dependent, resonance structure is observed not only for energies above the classical field-ionization limit, but above the zero-field ionization limit as well. A striking dependence of the cross section upon light polarization is also observed.

Laser implosion of 87-bar neon-filled glass microballoon targets produces a dense, cool plasma whose development in time and space is recorded by pulsed-x-ray shadowgraphy with soft x rays from a separate laser-produced plasma. Compressed densities of 4 g ${\mathrm{cm}}^{-3\mathrm{}}$ are estimated from the data by comparison with numerical simulations of the implosion.

The spectrum cascade by mode coupling in drift-wave turbulence occurs to larger and smaller values of $\left|\overrightarrow{\mathrm{k}}\right|$ rather than toward lower frequencies. This leads to the dual cascade process; energy cascades to smaller $k$ while enstrophy (square of the vorticity) cascades to larger $k$, analogous to two-dimensional hydrodynamic turbulence. However, the speed of energy condensation to $k=0\mathrm{}$ is much slower than in the hydrodynamic case.

The apparent incompatibility between a "spinning" texture in the bulk and the boundary condition at the surface is shown to be unreal. Topological arguments are used to show that this "incompatibility" can always be eliminated in both open and closed containers by appropriate textural arrangements. The "spinning" process in the bulk corresponds to a continuous nucleation of vortex rings. In an open geometry, these rings will flow downstream along the heat current. In a closed container, they will be devoured entirely by stationary singular loops at the surface.

The thermal conductivity of germanium doped with lithium in the isolated impurity range has been measured between 0.4 and 20 K. The analysis of the electron-phonon scattering leads, for the first time, to a determination of the valley-orbit splitting (0.12 meV) of the ground state of the interstitial Li donor in Ge.

The behavior of aqueous solutions of sodium octyl benzene sulfonate in high magnetic field is studied. The first and second critical micellar concentrations are determined. Moreover, and for the first time, fundamental results on the shape distribution of the micelles are unambiguously obtained in a wide range of concentrations ($0<~c<~\frac{1M}{1}$).

Applying the recently developed technique of neutron spin-echo spectroscopy, we found it possible to verify unambiguously the scaling predictions of the Zimm model: $\Delta \omega \sim q^3$ for the dynamics of a single chain. At higher polymer concentrations, experimental indications for the predicted crossover to many-chain behavior, which is accompanied by a change in exponent from 3 to 2, were observed. Line-shape analysis rules out a simple exponential decay, indicating the importance of memory effects.

Acoustic experiments on the metallic glass ${\mathrm{Pd}}_{0.775}$${\mathrm{Si}}_{0.165}$${\mathrm{Cu}}_{0.06}$ are presented which show a tunneling-system decay rate at 0.01 K enhanced by a factor of ${10}^4$ over insulating glass. A theory is presented for decay based upon the coupling of tunneling systems to conduction electrons, and the parameters of the theory are obtained from experiment. Relaxational absorption and dispersion in this amorphous metal are interpreted in terms of a tunneling model with a broad spectrum of decay rates.

We present results of dark-conductivity, photoconductivity, photoluminescence, and optical-absorption experiments on films of sputtered oxygenated amorphous-silicon-hydrogen alloys ($a-{\mathrm{Si}}_{1-x}{\mathrm{H}}_x$). Films with oxygen (O) are shown to behave much more like glow-discharge-produced $a-{\mathrm{Si}}_{1-x}{\mathrm{H}}_x$ than do O-free films. O is found to enter the amorphous matrix predominantly in an Si-O-Si bridging configuration. Defects associated with the presence of H are shown to be likely centers for radiative recombination, while both O and H may be associated with locally deformable defects.

A new experimental technique is introduced by which tunneling splittings of ground torsional-oscillator states in solids can be obtained directly. Rotating-frame time evolution of the spin-torsional system, monitored by the proton spin magnetization, is presented for N${\mathrm{H}}_4$I and C${\mathrm{H}}_3$C${\mathrm{D}}_2$I, along with the frequency spectra. The resolution of the spectral lines is an order of magnitude better than the magnetization-loss spectra.

By constant-initial-state photoelectron-yield spectroscopy in the 50-250-eV photon energy range, we have measured separately the $4d\to 4f$ photon absorption of $4f^5$ and $4f^6$ Sm atoms on the surface of evaporated Sm films. The $4f^6$ and $4f^6$ electron emission shows two spectrally distinct enhancements corresponding to $4d^{10}4f^5\to 4d^{9}4f^6$ and $4d^{10}4f^6\to 4d^{9}4f^7$ transitions. Since bulk photon absorption and constant-final-state yield shows only the first spectrum, surface and bulk electronic configurations can be distinguished.

We report on a new effect in superconductivity and demonstrate experimentally that, because of the correlation of the upper critical field $H_{c2\mathrm{}}$ with crystal directions in single-crystalline $\mathrm{Ta}\mathrm{N}$ samples (anisotropy effect), at certain fixed temperatures the material is a type-I superconductor near the [100] and a type-II superconductor near the [111] directions.

A dramatic increase in the width of the exchange-narrowed paramagnetic resonance line in ${\mathrm{Cu}}_{75}$${\mathrm{Mn}}_{25}$ is reported and shown to result from the critical dynamics of the spin-glass transition. The divergence of the linewidth as ${(T_f-T)}^{-1\mathrm{}}$ is the first observation of power-law behavior at the spin-freezing temperature.

We have measured the quasiparticle recombination time in the strong-coupled superconductor ${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$ directly by measuring the lifetime-broadened energy gap edge. This is done by measuring the $I-V$ characteristics of a superconducting tunnel junction of the type ${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$-insulator-${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$. Agreement with the calculated value is excellent.

We report an extra contribution to the extraordinary Hall effect in $\mathrm{Au}\mathrm{Fe}$ alloys as the ferromagnetic percolation limit is approached. It increases as the mean free path is reduced, and has the same sign as the extraordinary Hall effect in pure Fe. We suggest that it arises from the side jump of electrons moving in the ferromagnetic clusters that are formed with the emerging ferromagnetism.

Results of quantitative high-resolution absorption measurements in the range of the $w{}_{}{}^1{}_{}{}^{}\Delta _{\mathrm{u}}^{}{}_{}{}^{}\leftarrow X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}$ and $a{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{g}}^{}{}_{}{}^{}\leftarrow X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}$ derived exciton progressions in solid ${\mathrm{N}}_2$ are reported. The newly observed detailed fine structure of the vibrational bands is analyzed in terms of a sharp zero-phonon line and phonon-assisted exciton transitions. A theoretical analysis based on a strong-exciton-phonon-coupling model leads to good agreement with the observed experimental line shape.

Results of proton spin-lattice relaxation time ($T_{1n}$) measurements on ${\mathrm{C}\mathrm{u}\left(\mathrm{N}{\mathrm{O}}_3\right)}_2$·2½${\mathrm{H}}_2$O at $T=4.2\mathrm{}$ K for $5 \mathrm{kOe}<H<\mathrm{}60\mathrm{} \mathrm{kOe}$ are presented. The data are related to the spin fluctuations in the anisotropic (${J_E}^{\perp }=2\mathrm{}{J_E}^{\parallel }$) antiferromagnetic chains of effective spins $S^{\prime }=\frac{1}{2}$. The results compare favorably with the theoretical results of McFadden and Tahir-Kheli over the whole frequency range up to $8{\omega }_x$ $({\omega }_x=\frac{\left|{J_E}^{\perp }\right|}{\hslash })$.

The radius of gyration $R_s$ of two-dimensional clusters containing $s$ sites each is found to vary as $s^{\rho }$ for $10\lesssim s\lesssim 100$, with $\rho \simeq 0.66$ for percolation clusters below the threshold and for random animals, $\rho \simeq 0.54$ at the percolation threshold, and $\rho \simeq \frac{1}{2}$ for percolation clusters above threshold and for growing animals. The density profiles indicate that the percolation clusters have a relatively narrow surface layer (like raindrops) above $p_c$ but not below $p_c$.