It is shown that the final observed charge state of a field-evaporated ion can be explained by the occurrence of post-ionization whereby an ion being accelerated away from a metal surface in a strong electric field loses one or more electrons by tunneling into the substrate. Calculations using an approximate analytic formula derived from a simple model potential predict the probability of post-ionization for many different elements.

It is predicted that a nonequilibrium first-order phase transition analogous to optical bistability can occur when external coherent radiation is applied to a suitably prepared Josephson junction with an external resistance across it. The size of the hysteresis region can be tuned by varying the resistance.

It is shown that optical excitations of the $d$ shell may induce changes in the multiplet structure of the $3p$-photoelectron emission spectra of transition-metal compounds. The photoelectron spectra of ${\mathrm{Ni}}^{2+}$ and ${\mathrm{Cr}}^{3+}$ compounds in some excited states are calculated and compared with those in the ground states.

The effect of electromodulation of surface states on the electroreflectance of Ag(110) is investigated with use of results from a first-principles, self-consistent pseudopotential calculation of the surface electronic structure. Our model explains the polarization anisotropy observed on the (110) face of Ag, Cu, and Au. A broadening of the surface state by ∼ 1 eV is explained by interactions of water dipoles at the metal-electrolyte interface.

The conductivity of amorphous ${\mathrm{As}}_2$${\mathrm{Te}}_3$ and ${\mathrm{As}}_2$${\mathrm{Te}}_3$Ge was measured down to 4.2 K at frequencies ranging between 0.1 and 100 kHz. The ac conductivity below 100 K, which is totally unaffected by the dc conductivity, is proportional to ${\omega }^s{T}^n$ with $s=1\mathrm{}$ and $n\simeq 0.5$ for as-deposited films and $n\simeq 0.1$ for annealed films. These experiments are interpreted in terms of Elliott's theory based on electron pairs hopping over a barrier between both paired and random defects.

Recent measurements on $\mathrm{Cu}\mathrm{Mn}$ spin-glass alloys have revealed that the anisotropy field maintaining the remanent magnetization in the direction of the initial applied field is strongly enhanced by the addition of nonmagnetic Au or Pt impurities. We show that these results can be accounted for by the existence of Dzyaloshinsky-Moriya-type interactions between the Mn spins arising from spin-orbit scattering of the conduction electrons by nonmagnetic impurities. The magnitude of these interactions is surprisingly large.

A simple and very physical model to explain the magnetic properties of heavily doped, $n$-type semiconductors below the metal-nonmetal transition is proposed. Based on the wide distribution of exchange interactions between donors, this model establishes a hierarchy of exchange interactions accounting for the existence of the low-lying energy levels which determine the magnetization of the donor system at low temperature, and explain the absence of a transition to an ordered antiferromagnetic state.

It is shown that the generalized Ginzburg-Landau free-energy functional of Blount and Varma admits self-consistent solutions with quantized-flux vortices, magnetized in a region about the cores. There is a temperature range where the new phase has a lower free energy than either the pure superconducting or pure ferromagnetic phases; it represents true coexistence of ferromagnetism and superconductivity. The main features of the specific heat and magnetic properties of some rare-earth ternary compounds can be explained qualitatively.

Neutron profiles of spin waves in the $1d$ Ising-type antiferromagnet CsCo${\mathrm{Cl}}_3$ were reexamined. Instead of well-defined magnon peaks, the spin-wave spectrum consists of a band of magnon states arising from the motion of domain-wall pairs. At the magnetic zone center, the energy of this band extends from $2J(1-2\epsilon )$ to $2J(1+2\epsilon )$, whereas at the zone boundary a sharp resolution-limited peak at $\omega \sim 2J$ is observed.

The ground-state properties of a generalized quantum $s=\frac{1}{2}$ $\mathrm{XY}$ model (including the ferromagnetic and antiferromagnetic cases) in a $Z$ field on a triangular lattice are examined. The exact values of critical fields above which the gap opens are obtained. A real-space renormalization-group method is used to estimate the ground-state energy and to analyze the critical behavior. There is some evidence that certain features of frustration in classical spin systems still persist in quantum systems.

The adsorption and catalytic reactions of ${\mathrm{H}}_2$, CO, and ${\mathrm{O}}_2$ on Pt were investigated with a quartz-crystal microbalance having a sensitivity of ∼ ${10}^{-10\mathrm{}}$ g/${\mathrm{cm}}^2$ (<${10}^{-2\mathrm{}}$ monolayers of oxygen). At zero coverage the sticking coefficients for ${\mathrm{H}}_2$, CO, and ${\mathrm{O}}_2$ were 0.62, 0.54, and 0.38, respectively. The catalytic oxidation reactions all exhibited Langmuir-Hinshelwood behavior. Detailed rate curves were measured for the ${\mathrm{H}}_2$-${\mathrm{O}}_2$ reaction. The maximum reaction probability was 0.32 per impinging ${\mathrm{H}}_2$.

A one-electron atom in a general curved space-time is considered. The Hamiltonian of the Dirac equation is found in Fermi normal coordinates, and expressions are obtained, to first order in the Riemann tensor, for the shifts in energy of the $1S_{\frac{1}{2}}$, $2S_{\frac{1}{2}}$, and $2P_{\frac{1}{2}}$ levels.

Dipole anisotropy in the cosmic background radiation in the 500-3000-μm wavelength region has been measured in a balloon-borne experiment. A dipole amplitude was found with $T_D=\left({2.9}_{-0.6\mathrm{}}^{+1.3\mathrm{}}\right)$ mK, at R. A. = 11h 24m±0h 40m, $\delta =3\mathrm{}°\pm 10°$, the errors arising essentially from detector and magnetometer calibrations. This Letter also reports the existence of a second harmonic $T_Q=\left({0.9}_{-0.2\mathrm{}}^{+0.4\mathrm{}}\right)$ mK.

The total $\overline{p}p$ cross section has been measured in the $S$ region by the transmission method with use of a beam-monitoring spectrometer. The result is inconsistent with the existence of the narrow resonance $S\left(1936\right)\mathrm{}$ with cross sections reported by previous experiments.

It is shown, on the basis of an $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$-symmetric model, that the large-$N$ quantum theory can be described in terms of the classical equation of motion supplemented by some special boundary conditions. It is then exemplifyied how the appropriate classical solutions determine the sum of planar diagrams.

Cross sections for true absorption by nuclei (Al, Ti, Cu, Sn, Au) of pions (${\pi }^{\pm }$) in the energy range from 20 to 280 MeV were measured by a new method of detecting nuclear $\gamma$ rays following the reaction. The incident-energy dependence of the cross sections in the low-energy region ($T_{\pi }<50\mathrm{}$ MeV) was well reproduced by an optical-model calculation, while the higher-energy part seems to indicate complex mechanisms of pion absorption.

Configuration-interaction calculations show the existence of bound ${\mathrm{Li}}^{-}\left(1s2s2\mathrm{}{p}^2\right){}_{}{}^5{}_{}{}^{}P$ and ${\mathrm{Li}}^{-}\left(1s2\mathrm{}{p}^3\right){}_{}{}^5{}_{}{}^{}S_{}^{\circ }{}_{}{}^{}$ states lying 56.910 and 60.460 eV above the Li ground state, respectively. The ${}_{}{}^5{}_{}{}^{}S_{}^{\circ }{}_{}{}^{}$ state decays into the ${}_{}{}^5{}_{}{}^{}P$ state with $\lambda =3489.5\mathrm{}\pm 1.1$ Å and $\tau =2.86\mathrm{}\pm 0.10$ nsec. Experimental and theoretical evidence about an unclassified, cascade-free, medium-intensity line with $\lambda =3489.7\mathrm{}\pm 0.2$ Å and $\tau =2.9\mathrm{}\pm 0.2$ nsec in the beam-foil spectra of doubly excited lithium strongly suggests the presence of core-excited ${\mathrm{Li}}^{-}$ ions in the beam-foil source.

The behavior of a large number of coherently pumped three-level systems coupled to two resonant cavity modes at the two respective intermediate frequencies is shown to be qualitatively different from conventional laser-type behavior. The existence of three steady states and the dependence of their stability on the operating conditions allows the production of steady, modulated, or pulsed excitation of both modes.

A small-signal theory is given for gain in a free-electron laser comprising a cold relativistic electron beam in a helical periodic transverse, and a strong uniform axial, magnetic field. Exact finite-amplitude, steady-state helical orbits are included. If perturbed, these orbits oscillate about equilibrium, so that substantial gain enhancement can occur if the electromagnetic perturbations resonate with these oscillations. This gain enhancement need not be at the cost of frequency upshift.

A low-frequency torsional oscillator has been used to measure the temperature dependence of the in-plane shear modulus and dissipation of freely suspended films of butyloxybenzylidene octylaniline. It has been observed that smectic-$B$ films have a solidlike shear modulus and that the smectic-$B-A$ transition proceeds in at least two separate steps. The lower-temperature transition is the bulk melting while the higher-temperature transition is tentatively identified as surface melting.