The high-spin level structure of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Dy}$ has been determined through the (${}_{}{}^{34}{}_{}{}^{}\mathrm{S}$, $4n\gamma$) reaction. Lifetimes have been measured by use of the recoil-distance method. Both the level structure and lifetimes indicate a transition from collective to few-particle characteristics at high spin, possibly suggesting a changing shape from prolate through triaxial to oblate.

Theoretical calculations based on the rotating Woods-Saxon potential with optimized parameters indicate appearance of the superdeformed shapes with ${\beta }_2=0.6\mathrm{}$ already at $I\approx 52$ and simultaneously the triaxial-configuration minimum ($\gamma \approx 30°$) with ${\beta }_2\approx 0.3$. Two values of the moments of inertia viz. $2{\mathcal{I}}^{\mathrm{}\left(2\right)\mathrm{}}\approx \left(167\mathrm{} \mathrm{and} 125\right){\hslash }^2$ Me${\mathrm{V}}^{-1\mathrm{}}$ were deduced from our $E_{\gamma }-E_{\gamma }$ correlation measurement.

Photoejection of both electrons from the ${\mathrm{H}}^{-}$ ion by a single incident photon has been observed with use of a crossed-relativistic-beam technique. The dipole selection rules for a single photon pick out the ${}_{}{}^1{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}$ final state. The relative cross section was measured over a 0.30-eV range of photon energies near threshold in steps of 0.007 eV with a resolution of 0.007 eV full width at half maximum. The energy dependence of the cross section in this region was consistent with a Wannier threshold law.

It is shown that two light beams interacting in a third-order nonlinear medium undergo transition from a stationary to periodic and chaotic states, as their intensities are increased. A threshold for the onset of instabilities is calculated and verified by computer simulations. It is therefore proved that external feedback is not necessary for self-oscillations in nonlinear optical systems.

The energy bands, work function, Al $2p$ chemical shift, and oxygen binding energy have been calculated self-consistently for six-layer Al(111) films with oxygen overlayers at $Z=0.55, 0.60, \mathrm{and} 0.70$ Å above the Al surface plane. Because the work function is extremely sensitive to $Z$, it has been estimated with very small uncertainty, $Z=0.578\mathrm{}\pm 0.032$ Å. This value is in excellent agreement with the values obtained from the chemical shift and binding energy as well as Stöhr et al.'s experimental value.

The electron-phonon interaction is used to demonstrate the important effect of interactions on the electronic distribution function at finite temperature. It is shown that the usual picture of "thermal (Fermi) smearing" is a greatly oversimplified one. The distribution function resulting from an Einstein spectrum with various coupling strengths is presented and interpreted, and an exact expression for the spin susceptibility is used to illustrate the utility of this novel viewpoint for thermodynamics.

Oversaturated layers such as krypton on graphite are represented by a triplet helical Potts model, incorporating domain walls and antiwalls, and their crossings and annihilations (dislocations). Renormalization-group treatment yields a disordered phase between commensurate and incommensurate phases, down to zero temperature. Coadsorption produces a first-order transition directly between the commensurate and incommensurate phases, in analogy to temper embrittlement.

A novel cluster-expanded ab initio effective or model Hamiltonian is described and illustrated for a linear chain of hydrogen atoms. The method relies on expanding the model Hamiltonian in a sum of irreducible cluster interaction operators. A hierarchy of increasingly accurate ab initio Heisenberg spin Hamiltonians duplicate low eigenvalues of the more complete Schrödinger Hamiltonian. Finally these Heisenberg models are treated to obtain the ground-state energy and magnetic susceptibility of the infinite chain.

The rate of subcores in cosmic-ray air showers has been measured near sea level with a close-packed 35-${\mathrm{m}}^2$ array of spark chambers at Leeds. Auxiliary experiments demonstrate that our transition effects are negligible. The rate of subcores versus shower size is translated into the rate of high-$p_T$ events versus energy of the interacting hadron. Comparison with calculations of Halzen favors ${p_T}^{-4\mathrm{}}$ over ${p_T}^{-8\mathrm{}}$ scaling. The highest energy bin is centered on 350 TeV.

Account is taken of the dissipation of anisotropy due to neutrino viscosity and nearly collisionless radiation in a Bianchi type-I cosmology during primordial nucleosynthesis. For experimentally allowed cross sections, and for moderate anisotropy, the final ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mass fraction is significantly less than in the standard model, while the D fraction increases much less than would be expected in a low-helium isotropic cosmology.

In this experiment, an electron- and optical-holographic technique is employed with small toroidal ferromagnets each forming a magnetic-flux closure. The holographic interferometry proves that a phase difference between two electron beams having passed through the field-free regions agrees well with the fundamental relation known as the Aharonov-Bohm effect. It is also confirmed from the same hologram that flux leakage from the toroids does not affect the conclusion.

Three subclasses of stationary axially symmetric diagonal Weyl metrics satisfying the empty-space Einstein equations are presented in an explicit form. These solutions generalize the $C$ metric (mass with constant acceleration) and contain six free parameters. Four of these parameters appear as exponents playing a role similar to $\delta$ in the Tomimatsu-Sato solution (mass with quadrupole moment). For integer values of the exponents these metrics are constructed from rational functions only. Special cases include various metrics of physical interest.

A measurement is reported of charged multiplicity distributions of high-mass diffractive ${\pi }^{\pm }$, $K^{\pm }$, and $p^{\pm }$ states produced in 100 and 200 GeV/c hadron-proton collisions, $h+p\to X+p$. The distributions are described well by a Gaussian function that depends only on the available mass $M=M_x-M_h$, has a maximum at $n_0\cong 2M^{\frac{1}{2}}$, and a peak-to-width ratio $\frac{n_0}{D}\cong 2$.

It is shown that the charged multiplicity distributions of the diffractive and nondiffractive components of hadronic interactions, as well as those of hadronic states produced in a variety of other reactions, follow a universal function which depends only on the mass available for pionization. This function is Gaussian, peaks at $n_0\cong 2M^{\frac{1}{2}}$, where $M$ is the available mass in gigaelectronvolts, and has a width $D={(〈n^2〉-{n_0}^2)}^{\frac{1}{2}}$ such that $\frac{n_0}{D}\cong 2$.

A half-life measurement gives $(57\mathrm{}\pm 13)B_W$ for the 1575-keV $E3\mathrm{}$ transition in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Gd}$, which characterized the 2.572-MeV ${\left(\frac{19}{2}\right)}^{-}$ level as $\nu f_{\frac{7}{2}}\times 3^{-}\times 3^{-}$ two-phonon octupole state. This is the first identification of a nuclear two-phonon octupole excitation. The observed departures from harmonic vibration (twice the one-phonon energy and twice the transition rate) can be quantitatively understood in terms of the microscopic composition of the states, and can be derived from other observed features of the octupole vibrations in this region.

Optical excitation of an atom containing an isomeric nucleus should affect its internal conversion coefficient through modification of its bound-state electronic wave functions as well as by interaction with the outgoing electron. The extreme case of ${}_{}{}^{235m}{}_{}{}^{}\mathrm{U}$, which decays entirely by internal conversion and for which pronounced environmental effects on the half-life have been observed, is considered. Resonant (bound-state) effects on the lifetime and electron emission spectrum are predicted to occur with moderate-power cw laser irradiation.

The energy shift of $K$ electrons in heavy atoms due to the self-energy correction has been calculated. This process is treated to all orders in $Z\alpha$, where $Z$ denotes the nuclear charge. For the superheavy system $Z=170\mathrm{}$, where the $K$-shell binding energy reaches the pair-production threshold (${E_{1s}}^b\sim 2m{c}^2$), a shift of +11.0 keV is found. This shift is almost cancelled by the vacuum polarization, leaving a negligible effect for all quantum-electrodynamical corrections of order $\alpha$ but all orders of $Z\alpha$.

The stability of a two-dimensional plasma sheet with a small field component parallel to the normal direction of the sheet is studied by means of the energy principle of collision-free kinetic theory. Numerical computations show that, depending on the parameter regime, unstable perturbations exist. The mode resembles a tearing mode. The typical wavelength along the main magnetic field direction is comparable with the scale length of the equilibrium.

Light scattered near the incident wavelength from C${\mathrm{O}}_2$ laser-solid target interactions in oblique incidence shows the spectral signature of Brillouin scattering both in the backward and in the near specular directions. This instability is apparently seeded by broadband scatter from the critical density surface and then amplified in the underdense plasma. 60% of the incident light is scattered, and the Brillouin contribution to total scatter may be large if the source is also large.