A scaling-field representation of Wilson's exact renormalization-group equation is derived and used for the approximate calculation of critical exponents for the continuous-spin Ising model in three dimensions. The truncation of the hierarchy of scaling-field equations that retains only the four most relevant scaling fields yields the critical exponents $\nu \approx 0.60$, $\eta \approx 0.06$, and ${\Delta }_1\approx -0.47\mathrm{}$ (where ${\Delta }_1$ denotes Wortis's correction-to-scaling exponent).

Space-charge-separation electric fields have been measured in the expansion of laser plasmas generated by 40-psec, 1.06-μm laser pulses. The measurements were made at 2.5 and 5.0 mm from the carbon targets and on nanosecond time scales. Measured electric fields were as high as 1900 V/cm and exceed those expected from theory.

A possible mechanism is discussed for the hard—x-ray emission observed in vacuum spark plasmas. The mechanism is based on the hypothesis that in the process of a sausage instability in a plasma pinch the plasma can have very high resistivity due to the constriction and strong turbulence, so that the conduction current is virtually cut off. In such a case strong electric fields should appear which could accelerate the electrons and ions to produce hard x rays as energetic as 20 times the discharge potential. The kinetic energies of ions and electrons are calculated.

We report experimental evidence of wave coupling and penetration to the interior of a high-density magnetoplasma using a double-wave-guide antenna as a slow-wave structure. Reflection coefficients as low as 4% were observed. The experiment used 9-cm microwaves with a plasma of 11-cm diam. The relevance to lower-hybrid heating of tokamak fusion plasmas is discussed.

The effective mass and the $g$ factor of quasiparticles near the Fermi surface of a two-dimensional electron gas are calculated in the random-phase approximation and in the Hubbard approximation, and are compared with the experimental results for an inversion layer on a (100) surface of silicon.

Ultraviolet photoemission spectroscopy has been used to measure surface states on cleaved silicon with varying step-atom densities determined by low-energy-electron diffraction. For high step densities (∼ 10%) a new surface-state peak is found at an energy 0.4 eV higher than the main surface-state peak. These measurements are the first demonstration that surface-state photoemission spectra depend strongly on cleavage steps.

A simple model for the temperature dependence of charge transfer in organic donor-acceptor solids is presented. It is shown that under certain conditions a transition can occur from a state of smaller charge transfer below the transition temperature to one of larger charge transfer above. The possible relevance of these results to observed metal-insulator transitions in organic solids is discussed.

The Gutzwiller variational treatment for correlated electrons in metals is extended to finite temperatures. An expression for the spin susceptibility is derived to explain the strongly temperature- and concentration-dependent susceptibility observed in Si: P.

Raman and Brillouin scattering studies of Cs${\mathrm{H}}_2$As${\mathrm{O}}_4$ give no evidence for a central peak or a relaxing term in the self-energy of the ferroelectric soft mode. The previously reported gap between the transition temperature and the temperature at which the soft mode extrapolates to zero results from simple linear piezoelectric coupling which causes a 20°K difference between the free and clamped Curie temperatures.

We have measured, by means of Raman scattering from phonon polaritons, the frequency dependence of the damping function $\gamma (\omega , T_{\mathrm{rm}})$ of the soft $E$-symmetry phonon in PbTi${\mathrm{O}}_3$ at room temperature. Our result shows that the divergence of $\gamma (\omega , T)$ for $T\to T_c$ arises mainly from the frequency dependence of $\gamma (\omega , T)$ and that $\gamma (\omega , T)$ for a fixed frequency $\omega$ is simply proportional to the temperature. The apparent divergence of $\gamma (\omega , T)$ for $T\to T_c$ observed by Burns and Scott results from the temperature dependence of the soft-mode frequency.

The proton decays of $T_{>}$ states in ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sb}$ formed in the reaction ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}(p, n){}_{}{}^{119}{}_{}{}^{}\mathrm{Sb}$ (isobaric analog state) have been studied using a neutron-proton coincidence technique. Analogs of excited states are observed with a total strength which is approximately 50% of that of the cross section to the ground-state analog. These higher analog states decay predominantly with proton energies close to that of the ground-state analog decay.

We have measured the energy spectra, angular correlations, and number of continum $\gamma$ rays following several heavy-ion reactions. A separation of the spectrum into yrast and statistical cascades is clearly indicated for the heavier product nuclei studied ($Z\gtrsim 50$), but is not so obvious for the lighter ones. The yrast cascades associated with three particular reaction channels have been interpreted to give moment-of-inertia values for the highest-spin states in these channels (up to $60\hslash$).

Direct and indirect transitions to the lowest $2^{+}$ collective states are shown to interfere constructively in the pickup reaction ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ at 104 MeV, and destructively in the inverse stripping reaction ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}$ at 99 MeV.

A broad electric monopole excitation peaking at 6.4 MeV has been observed in the breakup of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ induced by inelastic electron scattering. The monopole cross section was obtained from the observed cross section by subtracting the electric-dipole contributions converted from photodisintegration cross sections by using the virtual photon theory, and also subtracting the magnetic multipole contributions obtained from a 180° electron-scattering experiment. The extracted monopole matrix element is 2.4±0.5 ${\mathrm{fm}}^2$.

A method is presented which permits rapid interpretation of the synchrotron patterns emitted by a charged particle moving in the uniform magnetic field of an oblique rotator. The analysis predicts a variety of intensity and polarization patterns that are compared with data from a number of pulsars. It also predicts the observed frequency dependence of the peak-to-peak separation of two double-peaked pulsars.

The family of Kerr solutions, with $\mathrm{}\left|a\right|<m$, is shown to be the unique pseudostationary family of black-hole solutions of the Einstein vacuum field equations when the event horizon is assumed to be nondegenerate.

We have studied direct electron-positron pair production by the collision of 200-GeV ${\pi }^{-}$ mesons with a neon target. The data consist of 622 direct pairs with momenta ranging from 10 MeV/c to 7.5 GeV/c. We have measured the total production rate to an accuracy of 10% and studied the relevant momentum and electron-positron momentum partition spectra. In contrast to several recent experiments, we find excellent agreement with the predictions of quantum electrodynamic calculations.

We present a comparative study of inclusive ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ production in $\mathrm{pp}$ collisions at 102 and 400 GeV/c. To better than 10% accuracy the invariant ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ cross section does not depend on energy. A remarkable similarity is observed between the properties of the neutral-baryon system produced in association with the ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ and the known characteristics of ${\pi }^{-}p$ collisions.

For multiphoton processes, the higher-order terms of the perturbation series are treated by summing the class of irreducible diagrams. This allows the examination of the behavior of the cross section as a function of the incident photon flux at arbitrarily large intensities by means of analytic continuation to the nonperturbative region. The case of four-photon ionization of the ground state of hydrogen is discussed as an example.

The ($e, 2e$) reaction promises to be an extremely sensitive probe for molecular wave functions. As an initial test we have applied it to the ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ molecules in order to investigate its sensitivity to electronic and vibrational details. A detailed configuration-interaction wave function fits the data, whereas simpler functions do not. The simple Born-Oppenheimer approximation is confirmed to the accuracy of the experiment. The probe is compared with the Compton profile as a means of investigating the electron momentum distribution in ${\mathrm{H}}_2$.