A simple Lane model is used to parametrize the energy systematics of the isospin splitting of high-spin magnetic states in non-self-conjugate nuclei. A strength parameter $V_1=106\mathrm{}\pm 10$ MeV is found.

This paper reports measurements of the lifetimes of fourteen levels in the $3s$, $3d$ complex of para-${\mathrm{H}}_2$ by a delayed coincidence method. A collimated beam of metastable hydrogen molecules was selectively excited by light pulses from a cw dye laser and fluorescent radiation was detected by a vacuum ultraviolet photomultiplier. The observed lifetimes range from 11.1 to 48.8 nsec. Similar methods can be used to determine the structure and lifetimes in other excited states of ${\mathrm{H}}_2$ and in a variety of other systems.

The observation of a resonant photoemission line in atomic copper (Cu vapor) is reported. Several two-electron satellites are observed below the $3p$ ionization threshold; only one multiplet ($3d^{8}4s^2{}_{}{}^1{}_{}{}^{}G_4^{}{}_{}{}^{}$) shows an appreciable resonance, in agreement with theory.

A pure rotational $U$-type transition ($\Delta J=4\mathrm{}$) in solid parahydrogen has been recorded by using a high sensitivity infrared spectrometer. On the assumption of a rigid lattice, the measured intensity led to a value of 0.335 (in atomic units) for the hexadecapole moment of molecular hydrogen. Electric quadrupole-quadrupole interaction effects have been identified in the spectra. It appears possible to extract the phonon density of states in solid ${\mathrm{H}}_2$ from the phonon branch ${U_0}^R\mathrm{}\left(J\right)\mathrm{}$.

A one-electron treatment of the ${\mathrm{H}}^{+}$-${\mathrm{H}}^{-}$ collision is proposed which is not restricted to neutralization into $\mathrm{H}\mathrm{}(n=2\mathrm{})\mathrm{}$+H, is free from two-state-crossing models, and involves an electron translation factor. Diabatic states are found to differ from those conventionally invoked. Neutralization into $\mathrm{H}\mathrm{}(n=3\mathrm{})\mathrm{}$+H is put forward and detachment is interpreted as a dynamic polarization effect. Agreement with available experiments is found above 200 eV (c.m.). Below this energy puzzling discrepancies persist.

It is demonstrated by experiments and supporting particle simulations that the forward Raman instability is capable of producing extremely high-energy electrons in an underdense plasma. The instability has a high saturation level for the electrostatic wave component. Its consequences and applications to the laser electron accelerator and the laser-fusion pellet preheat are discussed.

Disk targets of Be, CH, Ti, and Au have been irradiated with 0.53-μm laser light in 3-30-J, 600-ps pulses, at intensities from 3×${10}^{13}$ to ∼4×${10}^{15}$ W/${\mathrm{cm}}^2$. The measured absorptions, hard-x-ray fluxes, and sub-keV emission properties are compared with hydrocode simulations. The results show strong collisional absorption, some Brillouin scattering, little suprathermal electron production, and efficient conversion of absorbed energy into sub-keV x rays, in general accord with wavelength-scaling predictions.

The energy dependence of the introduction rates of the main defects created in GaAs by electron irradiations in the two crystallographic directions [111] and [$\overline{1}\overline{1}\overline{1}$] have been measured. It is demonstrated that the defects introduced are caused by displacements of As atoms and not of Ga atoms, as previously believed. We show that the observed anisotropy can be explained by an orientation dependence of the threshold energy in the range 7-11 eV.

Three-dimensional bond orientational order is studied via computer simulations of 864 particles interacting through a Lennard-Jones pair potential. Long-range orientational fluctuations appear upon supercooling about ten percent below the equilibrium melting temperature. The fluctuations suggest a broken icosahedral symmetry with extended correlations in the orientations of local icosahedral packing units.

The ${\mathrm{O}}^{+}$ ion yield above the $\mathrm{O}\mathrm{}\left(1s\right)\mathrm{}$ absorption threshold ($K$ edge) from CO on Ni(100) is found to deviate significantly from the absorption coefficient. It exhibits a delayed onset by more than 20 eV with a broad maximum more than 100 eV above the threshold. This indicates the dominance of multielectron excitations over Auger deexcitation as the bond-breaking step for ${\mathrm{O}}^{+}$ desorption from chemisorbed CO molecules. Fine structure in the ${\mathrm{O}}^{+}$ yield around 50 eV above threshold is assigned to a resonant shake-off process.

The pressure of solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured as a function of temperature and molar volume down to and through its nuclear ordering temperature. Pressure measurement above the ordering temperature reveals that besides the known $\frac{1}{T}$ term there are a significant negative term in $\frac{1}{T^2}$ and a positive term in $\frac{1}{T^3}$. The observed discontinuous change in pressure through the ordering temperature is discussed in connection with the first-order phase transition.

An experimental small-angle x-ray scattering study of a phase-separating quasibinary glass ${\mathrm{B}}_2$${\mathrm{O}}_3$-PbO(${\mathrm{Al}}_2$${\mathrm{O}}_3$) is compared with the predictions of nonlinear theories for advanced stages of decomposition. The time evolution of the moments and the scaling of the structure function show a reasonable agreement, suggesting the validity of the scaling hypothesis in glassy systems.

The low-temperature specific heat of potassium has been remeasured and evidence for the existence of phasons is found. The fraction of phonons converted to phasons is 2×${10}^{-5\mathrm{}}$ and the Debye temperature of these phasons is 6 K.

Spin-polarized, energy-resolved photoemission using monochromatized synchrotron radiation shows that the 6-eV satellite of Ni is highly spin polarized near to the $3p-3d$ excitation threshold ($h\nu \approx 65$ eV). This observation proves the validity of the model involving $M_{2,3}{M}_{4,5}{M}_{4,5}$ Auger transitions with final localized two-hole bound states and rules out explanations within a one-electron band picture.

Self-consistent, first-principles electronic-structure calculations were carried out for Li${\mathrm{C}}_{18}$, a model high- (third-) stage graphite intercalation compound. The results illustrate the charge distribution and screening mechanisms in this class of compounds and account for many of their unusual electronic properties. The total charge transferred is found to be well concentrated on the bounding carbon layers, while the conduction-electron contribution is much more delocalized.

The spin polarization of the photoelectric current from ferromagnetic gadolinium is expected to decrease monotonically on increasing the photon energy $h\nu$ from threshold to about 10 eV. However, it is found experimentally that a pronounced minimum in the polarization occurs at $h\nu =6.5\mathrm{}$ eV. It is shown that this minimum is due to a quasielastic decay of the optically excited $4f^8$ state into a $5d$ band state.

The velocity dependence of the ionization probability of sputtered ${\mathrm{O}}^{-}$ from chemisorbed oxygen layers on V and Nb is studied. The ionization probability is found to depend on the normal component of the emission velocity, which suggests that the ionization process is an ion-surface interaction and not an ion-atom binary interaction. For $v_{\perp }>1\mathrm{}\times {10}^6$ cm/sec, the ionization probability shows an exponential dependence on $v_{\perp }$. However, this velocity dependence fails at lower velocities.

Measurements are reported of the magnetization, magnetic ordering, and optical absorption of mixed single crystals of Dy$\left({\mathrm{P}}_{1-x}{\mathrm{V}}_x\right)$${\mathrm{O}}^4$. This compound is shown to be a good example of a system with random spin anisotropy. In contrast to the results on ${\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x{\mathrm{Cl}}_2$, no tetracritical point is found, and long-range magnetic order is destroyed by rather small concentrations of the minority component. These results agree with recent theories on random-anisotropy systems.

A rate is calculated of nonradiative recombination in which a deep-level defect captures first an injected minority carrier and then a majority one by multiphonon emission. In many cases the second capture occurs in a very short time, of the order of a phonon period, during lattice relaxation toward a new equilibrium configuration triggered by the first capture. The mechanism gives a model of the so-called killer centers which cannot be detected by measurements of trapped carriers.

The light-scattering techniques of intensity angular dissymmetry and photon correlation spectroscopy are used to determine the static correlation length, osmotic compressibility, and diffusivity of an oil-in-water microemulsion. The observed temperature dependence of these quantities near a phase separation point qualitatively resembles the critical behavior found for simple fluids and binary mixtures, but with substantially larger values of the critical exponents $\tilde{\nu }$ and $\tilde{\gamma }$.