Measurements of Zeeman transitions in the ground state of muonium at strong magnetic field have yielded values for the hfs interval, $\Delta \nu =4463\mathrm{}302.35\left(52\right)\mathrm{}$ kHz (0.12 ppm) and for the muon magnetic moment, $\frac{{\mu }_{\mu }}{{\mu }_p}=3.183\mathrm{}3403\left(44\right)\mathrm{}$ (1.4 ppm), of considerably higher precision than previous results. The theoretical expression for $\Delta \nu$, including our measured value of $\frac{{\mu }_{\mu }}{{\mu }_p}$, disagrees with the experimental value by 2.5 standard deviations. The electronic $g_J$ density shift for muonium in Kr has been measured.

We have measured the narrow-beam x-ray attenuation coefficient for gaseous hydrogen, at energies of 6.46, 14.4, 22.1, and 25.0 keV. The uncertainties are smaller than 1% for all results. The data support theoretical predictions which take account of molecular effects.

Parametric excitation of the electrostatic ion cyclotron waves in a multi-ion-species plasma is observed. The modes are excited when the pump frequency is near the sum of the ion cyclotron frequencies. The dispersion relation and the threshold for excitation are measured.

The "direct interaction approximation" of Kraichnan as modified by Kadomtsev is employed to develop a strong turbulence theory which predicts both nonlinear frequency broadening and a power law for the spectrum of a two-dimensional convecting plasma.

Motion near a separatrix (the boundary between closed and open orbits) is studied both theoretically and numerically for parameters appropriate to the dissipative trapped-ion mode. I observe disappearance of an invariant in a stochastic layer surrounding the separatrix, as a result of overlapping bounce resonances. The fraction of ions lying within the stochastic layer is large even for a mode of relatively small amplitude.

The specific heats of monolayer ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ films adsorbed on Ar-plated Grafoil show prodound differences from films on bare Grafoil. The apparent liquefaction temperature of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is doubled, and the interacting Fermi gas behavior of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is modified to show either condensation or strong band effects.

A Monte Carlo study of a triangular lattice gas model appropriate to ${\mathrm{He}}^4$ monolayers adsorbed on the basal plane of graphite reveals a rich variety of critical and multicritical points including a new, special type of "bicritical" point.

The two-dimensional plasmon of an $n$ inversion layer of (100) $p$-type Si is observed at a fixed wave vector as a function of electron density. The position, width, and strength of the resonance agree with existing theory at electron densities ≳${10}^{12}$/${\mathrm{cm}}^2$. At lower densities, the resonance position is below the predicted value, implying a substantial increase in the electron mass.

Diffuse neutron scattering on the intermediate valence compound Ce${\mathrm{Pd}}_3$ shows a quasielastic line with Lorentzian shape and very large, nearly temperature-independent width ($\frac{\Gamma }{2}\simeq 20$ meV). The intensity under this line has $4f$ form factor but the total cross section indicates only 0.5 $4f$ electron per formula unit. These observations are interpreted by spontaneous relaxation of the local $4f$ magnetization due to interconfiguration fluctuation between $4f^1$ and $4f^0$.

The compound Er${\mathrm{Rh}}_4$${\mathrm{B}}_4$ becomes superconducting at a critical temperature $T_{c1\mathrm{}}$ of 8.7 K followed by a return to the normal state at a second critical temperature $T_{c2\mathrm{}}$ of 0.9 K. The return to the normal state at $T_{c2\mathrm{}}$ is coincident with the occurrence of long-range ordering of the magnetic moments of the ${\mathrm{Er}}^{3+}$ ions which completely occupy a set of equivalent lattice sites.

We have measured in the central region, the ratio of negative pion pairs to that of negative-positive pion pairs as a function of the Kopylov variables. A correlation was observed. From the shape of the correlation function we determined the radius $r$ and life-time $\tau$ of the centrally produced hadronic matter parallel and perpendicular to the collision axis to be $r_{\parallel }={0.73}_{-0.11\mathrm{}}^{+0.10\mathrm{}}$ fm, $r_{\perp }={1.65}_{-0.99\mathrm{}}^{+3.56\mathrm{}}$ fm, and ${\tau }_{\parallel }=\left({1.97}_{-0.56\mathrm{}}^{+0.57\mathrm{}}\right)\times {10}^{-24\mathrm{}}$ sec.

We have measured the differential cross section for proton-proton bremsstrahlung at sixteen photon angles for 730-MeV incident protons. At all angles, the photon spectra fall smoothly with increasing photon energy up to $E_{\gamma }\sim 80$ MeV and are in quantitative agreement with the prediction of external-emission dominance (EED). Above $E_{\gamma }\sim 80$ MeV the spectra are consistently above the EED calculations.

This Letter reports measurements for the processes $a+p\to a+X$ where $a$ is ${\pi }^{\pm }$, $K^{\pm }$, or $p^{\pm }$ over range of the Feynman $x$ from 0.7 to 0.975 at Fermilab energies. The data for all reactions are well represented by a simple parametrization. The cross sections show significant energy dependence in the high-$x$ region. While the data are consistent with factorization in the high-$x$ region and small $t$, the proton data are inconsistent with factorization for $x\lesssim 0.9$.

It is shown that if the Higgs boson mass exceeds $M_c={\left(8\mathrm{}\pi \frac{\sqrt{2}}{3G_{\mathrm{F}}}\right)}^{\frac{1}{2}}$ partial-wave unitarity is not respected by the tree diagrams for two-body reactions of gauge bosons, and the weak interactions must become strong.

Inclusions in mica which contain $\alpha$ emitters together with some water produce long-range protons via the scattering reaction ${}_{}{}^1{}_{}{}^{}\mathrm{H}(\alpha , \alpha )p$. It is shown that the radial dependence of the proton ionization density can account for the giant halos which have recently been the subject of searches for superheavy elements.

Radiationless relaxation following excitation of high levels of the $A{}_{}{}^2{}_{}{}^{}\Pi$ manifold in CN is shown to proceed via an interstate cascading mechanism involving the $A{}_{}{}^2{}_{}{}^{}\Pi$ and $X{}_{}{}^2{}_{}{}^{}\Sigma$ vibrational levels. The direct vibrational relaxation within the $X{}_{}{}^2{}_{}{}^{}\Sigma$ state is shown to be slower by at least 2-3 orders of magnitude. Experimental results and a theoretical discussion of these phenomena are presented.

We report optical second-harmonic generation in gases in a transverse dc magnetic field. An electric quadrupole moment of sodium or calcium vapor is induced by a two photon transition. The effect of the magnetic field is to transform the wave function within both the ground and the excited magnetic sublevels, and to make a new component of the quadrupole moment which can generate a collinear second harmonic. Transverse magnetization is not important in the present case.

Experimental measurements of the scattered infrared emission in the vicinity of 10 μm are presented. The shape and power dependence of the backscattered spectrum indicates the presence of the Brillouin backscatter instability. The sidebands on the side-scattered radiation are found to be strongest for emission perpendicular to the electric field vector of the incident radiation. This is interpreted as being the result of the parametric decay instability.

A steady-state spherical model has been used in this Letter to study the influence of light pressure on plasma flow and density profile modifications. Whereas in former investigations transitions from subsonic to sonic or supersonic flow and the concomitant formation of density steps have been studied in plane models, this paper treats the transition from supersonic to supersonic flow; and the new phenomenon of density plateau formation just below the critical density is found.