Thomson radar returns from the ionosphere subjected to a step-function excitation of electromagnetic waves show the immediate rise of electrostatic waves near the resonant height ${\omega }_p\simeq {\omega }_0$. The observed secular temporal variation $E\propto t$ agrees with a theory based on direct conversion of electromagnetic waves to electrostatic waves by preexisting density inhomogeneities. The rise time is at least an order of magnitude smaller than previously reported. The frequency spectrum shows this conversion is characterized by frequencies at the pump frequency ${\omega }_0$.

Observations are reported of magnetospheric hydromagnetic (Alfvén) waves excited by rapid changes in ionospheric conductivity induced by solar flare x-ray and extreme-ultra-violet fluxes. The observed wave frequencies (∼0.01-0.02 Hz) are those expected for fundamental eigenoscillations of the geomagnetic field at middle latitudes. The measurements confirm a natural hydromagnetic wave generation mechanism not associated with the solar wind or geomagnetic storms. These results have implications for Alfvén wave generation in other cosmic plasmas.

Starting with some observations due to A. B. Zamolodchikov, a short cut to the determination of the Baxter (eight-vertex) -model free energy is developed. The method involves factorizable $S$ matrices in 1 + 1 dimensions, which are briefly reviewed. If the method generalizes, we may associate with each known $S$ matrix a Baxter-like model with a known free energy.

A new variational principle is derived through the construction of the action in terms of a new set of canonical coordinates. The main advantage of this set of coordinates is that they contain exclusively information concerning the Eulerian description of the flow.

A system is proposed for detecting the effect of a weak classical force on a macroscopic mechanical oscillator. The novel feature is a type of ac bridge coupled to a SQUID amplifier. A detailed sensitivity calculation for one type of bridge excitation is reported which shows what is required to reach the standard quantum "limit." Another type of excitation should make it a "back-action evasion" device capable of exceeding the standard quantum "limit".

A triangular, half-infinite, nearest-neighbor Ising system is studied whose coupling strengths close to the boundary are weaker than those in the bulk. The deviations decay as $-\frac{A}{m^y}$ with the distance $m$ from the boundary. By means of a repeated star-triangle transformation the boundary spin-spin correlation $g\left(\mathcal{r}\right)$ is studied for critical bulk coupling. For $y=1\mathrm{}$ the behavior is $g\left(\mathcal{r}\right)\sim \frac{1}{{\mathcal{r}}^{\eta }}$ as $r\to \infty$, with a nonuniversal exponent $\eta$ depending on $A$. For $0<y<\mathrm{}1\mathrm{}$ anomalous decay $g\left(\mathcal{r}\right)\sim \exp [-{\left(\frac{r}{\xi }\right)}^{1-y}]$ is found. Expressions for $\eta$ and $\xi$ in terms of $A$ and $y$ are given.

The small-angle elastic scattering for $\mathrm{pp}$ at $\sqrt{s}=23.5, 30.7, \mathrm{and} 52.8$ GeV and for $\overline{p}p$ at $\sqrt{s}=52.8\mathrm{}$ GeV are measured. The data are normalized on Coulomb scattering. Using the optical theorem and the best estimate of the real part of the forward scattering amplitude, $\rho \left(p\overline{p}\right)=0.1\mathrm{}$, we obtain ${\sigma }_{\mathrm{tot}}\left(\overline{p}p\right)=44.1\mathrm{}\pm 2.9$ mb for the total cross section and $b\left(\overline{p}p\right)=13.6\mathrm{}\pm 2.2$ ${\mathrm{GeV}}^{-2\mathrm{}}$ for the nuclear slope parameter. This supports the dispersion relation prediction that ${\sigma }_{\mathrm{tot}}\left(\overline{p}p\right)$ will start to rise above $E_{\mathrm{lab}}\approx 200$ GeV.

The nuclear relaxation rate has been measured in spin-polarized hydrogen. The rate is so low that a gas composed of atoms initially in the two nuclear spin states spontaneously acquires a high nuclear polarization as one of the states recombines. The remaining state is stable against recombination, but decays slowly by nuclear relaxation. Nuclear polarization greater than 99% has been achieved. The absorption energy and the recombination rate of hydrogen have also been measured on liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

Two-photon transitions in the far-infrared spectral range have been observed for the first time. The magnetophotoconductivity of $n$-GaAs measured by a pulsed high-power C${\mathrm{H}}_3$F molecular laser at $\lambda =496\mathrm{}$ μm exhibited two-photon transitions between $1s$ and $2s$ shallow donor states and two-photon cyclotron resonance. The experimental results and symmetry considerations indicate that the observed two-photon cyclotron resonance is caused by impurities.

The fluorine $K\alpha$ x-ray spectra produced by 5.5-MeV ${\mathrm{He}}^{+}$ bombardment of a series of alkali and alkaline-earth fluorides were measured with a curved-crystal spectrometer. An anomalously low intensity of the $K{L}^1$ peak arising from $1s^{-1\mathrm{}}{\mathrm{}\left(2s2p\right)\mathrm{}}^{-1\mathrm{}}$ initial states was observed for KF and Sr${\mathrm{F}}_2$. Evidence is presented for a resonant electron-transfer mechanism associated with the formation of a molecule-ion between adjacent cation and anion sites.

Essentially identical pretransitional smectic $A$ behavior is reported in both normal and reentrant nematic phases of mixtures of octyloxycyanobiphenyl (8OCB) and hexyloxycyanobiphenyl (6OCB). A phenomenological model which assumes an optimum density for smectic interactions explains quantitatively our correlation length measurements for six different mixtures.

With the incident "beam" provided by the standing-wave pattern which on passing the Bragg reflection range in a silicon crystal is sweeping the atomic sites, the spectrum of inelastically scattered x-ray photons has been measured for appropriately chosen scattering vectors $\overrightarrow{\mathrm{q}}$. The results confirm the recent prediction that the spectrum is determined by the projections of the nondiagonal elements of the one-electron momentum-space density matrix $\Gamma \left(\overrightarrow{\mathrm{p}}\right|{\overrightarrow{\mathrm{p}}}^{\prime })$ on $\overrightarrow{\mathrm{q}}$.

This paper reports a study of the effect of the electron-phonon interaction on the magnetization below the Curie point of an itinerant-electron ferromagnet. From a numerical calculation on a simple model, it is found that the size of the effect can be much larger than the generally assumed value of $\sim \frac{\hslash {\omega }_{\mathrm{D}}}{{\epsilon }_{\mathrm{F}}}$ in the units of Bohr magneton per atom, where ${\omega }_{\mathrm{D}}$ and ${\epsilon }_{\mathrm{F}}$ are, respectively, the phonon Debye frequency and the electron Fermi energy.

The spectral density of the voltage noise has been measured in current-biased resistively shunted Josephson junctions in which quantum corrections to the noise are expected to be important. The experimental data are in excellent agreement with theoretical pretions, demonstrating clearly the contribution of zero-point fluctuations that are generated in the shunt at frequencies near the Josephson frequency and mixed down to the measurement frequency.

The electrical conductivity of the quasi-one-dimensional conductor ${\mathrm{Cs}}_2$[${\mathrm{Pt}{\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4\left]\right({\mathrm{N}}_3)}_{0.25}$·0.5${\mathrm{H}}_2$O, CsCP(${\mathrm{N}}_3$), has been studied. Values for the intrachain band filling and electronphonon coupling as well as for the electronic interchain coupling are compared to those of the well studied tetracyanoplatinate complexes. The physical properties of CsCP(${\mathrm{N}}_3$) are explained from its structure and characteristic hydrogen bonding.

The electronic structure of a C${\mathrm{U}}_{0.9}$${\mathrm{Al}}_{0.1}$(100) single crystal has been studied with use of an angle-resolved photoemission technique. An intrinsic Tamm-type surface state is found to exist in the disordered alloy. The linewidth of the surface state is analyzed to deduce the disorder-induced smearing of energy levels. These and other experimental results are discussed in terms of the computed band structure of the alloy on the basis of coherent-potential approximation applied to a realistic muffin-tin Hamiltonian.

Fast heavy ions in definite charge states have been used to desorb molecular ions. Samples of ergosterol, glycylglycine, and cesium iodide were exposed to 20-MeV oxygen ions in charge states $2^{+}$ to $8^{+}$. For the first time it has been shown that the yields depend strongly on the charge state of the primary ion. Existing models for "sputtering" fail to reproduce the measured yield distributions. The results illustrate that future desorption experiments should be carried out with primary ions in well defined charge states.

If the long-distance properties of pure gauge theories are described by thin strings, then quantum fluctuations induce a long-range spin-spin potential between widely separated heavy quarks. This potential falls off as the fifth power of the distance between the quarks and may be important in heavy-quark phenomenology.

Quantum Hamiltonian systems of lattice type are considered which are associated with classical finite-dimensional Lie algebras [like MH(2), SO(3), etc.], and possess complete integrability properties. The canonical Heisenberg $p_n$, $q_n$ variables are found for these Hamiltonian systems and it is shown how to construct their $S$ matrices. These new Hamiltonians are generalizations of the quantum Toda lattice Hamiltonian as well as $\mathrm{XXX}$ models of statistical mechanics.

A new integral equation which linearizes the Korteweg-de Vries and Painlevé II equations, and is related to the potentials of the Schrödinger eigenvalue problem, is presented. This equation allows one to capture a far larger class of solutions than the Gel'fand-Levitan equation, which may be recovered as a special case. As an application this equation, with the aid of the classical theory of singular integral equations, yields a three-parameter family of solutions to the self-similar reduction of Korteweg -de Vries which is related to Painlevé II.