A new search for the decay ${K_L}^0\to {\mu }^{+}{\mu }^{-}$ has been performed at the Brookhaven National Laboratory alternating-gradient synchrotron. We used the experimental technique employed by Carithers et al., with some modifications to suppress the background further and eliminate possible systematic effects. The analysis of this experiment yields three events satisfying criteria for this decay mode.

We have recently shown that the position and residue of the $S$-matrix pole of the $\Delta \mathrm{}\left(1236\right)\mathrm{}$ are unique, independent of the particular resonance formula used, thus resolving a discrepancy among phenomenological fits. Unlike the $P_{33}$ partial wave, the $P_{11}$ resonance is highly inelastic, very broad, and has a large background. This produces huge uncertainties in its mass and width, depending on the parametrization used. We report here that the position of the $N\left(1470\right)\mathrm{}$ pole is uniquely determined, $1380-110i$ MeV, from fits to the CERN phase shifts.

Vibrational excitation of ${\mathrm{O}}_2$ by electrons in the energy range 4-15 eV is studied with a crossed-beam double electrostatic analyzer. The differential vibrational cross sections for $v=1-4\mathrm{}$ at 25° show a bell-shaped energy dependence peaked near 9.5 eV. The observations are interpreted in terms of resonant contributions by excited states of ${\mathrm{O}}_2^{-}$. There is also evidence for the resonant enhancement of electronic excitations.

The lattice repeat distance of a nearly perfect single crystal of silicon has been measured in terms of the visible wavelength of a stabilized He-Ne laser. This crystal subsequently has been used to diffract reference x-ray lines ($\mathrm{Cu} K{\alpha }_1, \mathrm{Mo} K{\alpha }_1$) thereby establishing their wavelength relative to visible standards. In terms of the x-ray scale in which $\lambda \left(\mathrm{Cu}K{\alpha }_1\right)=1.537\mathrm{}400$ kxu, the conversion factor is ${\Lambda }_{\mathrm{Cu}}=1.002\mathrm{}0802$ Å/kxu (1 ppm); if $\lambda \left(\mathrm{Mo}K{\alpha }_1\right)=0.707\mathrm{}831$ kxu, ${\Lambda }_{\mathrm{Mo}}=1.002\mathrm{}1017$ Å/kxu (0.6 ppm).

A bolometric technique is used to determine the $g$-factor anomaly $a$ of the free electron from measurements made on 78°K electrons contained in a Penning-style quadrupole ion trap. The value obtained is $a=0.001\mathrm{}159667\left(24\right)\mathrm{}$, where the electron $g$ factor is given by $g=2\mathrm{}(1+a)\mathrm{}$.

Liquid-deuterium samples initially at 21°K and 1 atm were shock compressed to pressures of 200 and 900 kbar and temperatures of 4500 and 7000°K, respectively. The 900-kbar points were obtained by reflecting the 200-kbar shock wave from a brass cover. A theoretical model which uses an effective intermolecular pair potential gives reasonable agreement with the data. Using this potential we obtain a lower limit for a metallic phase transition at 1.7 ${\mathrm{cm}}^3$/mole and at 4.2 and 4.8 Mbar for ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$, respectively.

Ion Bernstein waves are excited by a long wire in the center of a potassium $Q$-machine plasma column. Because the wave vector is very nearly perpendicular to the magnetic field, we observe pure ion Bernstein waves, in contrast to neutralized ion Bernstein waves which were previously observed. The frequency bands for the cyclotron damping are so narrow that we can distinguish the isotopes of potassium.

Ohmic discharges with and without a limiter are being studied in the Heliotron D. Without the limiter, we observe longer containment time and lower impurity concentration than with the limiter, and a stable current with the safety factor $q_{0H}\simeq 0.4$ is obtained. With the limiter, strong current fluctuations are observed near rational values of the rotational transform, i.e., $\frac{\iota }{2\pi }=\frac{({\iota }_F+{\iota }_{0H})}{2\pi }\simeq 0.5 \mathrm{and} 1.0$.

Raman scattering studies of the $J=0\mathrm{}\to 2$ rotational transitions in solid parahydrogen and orthodeuterium over the pressure range $0<~p<~3.3$ kbar have revealed a phase transition from hcp to fcc, with the fcc structure being stable at high pressures and hcp stable at low pressures (≲ 0.8 kbar). In both phases the main anisotropic interaction is molecular electric quadrupole-quadrupole ($\sim R^{-5\mathrm{}}$), but we observe significant effects tentatively attributed to correlated zero-point motion.

Paramagnetic resonance of the self-trapped excition has been studied in KBr. The general features of the spectra confirm the validity of Kabler's model of a $V_K$ center having trapped an electron. We describe special aspects of the optical technique used to detect the resonance.

Phase shifts that describe the scattering of conduction electrons by impurity atoms incorporated substitutionally in a silver lattice have been deduced from experimental Dingle-temperature data. The results are consistent with a Friedel model of the electronic structures of the impurity states.

Experiments are reported which measure the relaxation properties of nuclei near a paramagnetic impurity. For ${\mathrm{Y}\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{S}{\mathrm{O}}_4\right)}_3$·9${\mathrm{H}}_2$O: ${\mathrm{Yb}}^{3+}$, nuclei as close as 3 Å to the Yb ion are in strong thermal contact with the bulk spins, contradicting the traditional notions of the diffusion barrier. I present evidence that impurity-induced diffusion and interaction with the electron spin-spin reservoir are important processes which act to reduce the barrier dimension.

We have measured the critical heat current in thermal counterflow in He II as a function of temperature. The results are analyzed in terms of a slightly modified Vinen theory. The agreement between theory and experiment is excellent, providing an independent determination of the parameters of the theory, as well as one of the few examples of a successful theory of critical-velocity phenomena in liquid He II.

Intermolecular and second-order light scattering in the condensed phases of hydrogen at para concentrations ranging from 25% to 96% have demonstrated the existence of underdamped short-wavelength collective excitations in the liquid phase over this concentration range and their relation to phonon excitations in the solid.

By solving the hydrodynamic equations for the parametric instability including modecoupling terms, we predict the saturation level and turbulent spectrum for the oscillating two-stream instability. Coupling the electron distribution function to the spectrum with the quasilinear diffusion coefficient gives the heating rate and high-energy tail formation. These predictions agree with the results of particle simulations.

The pair-correlation function for a one-component, two-dimensional classical plasma is investigated within the framework of the Debye approximation along the lines of the Cohen-Murphy method through a potential of average force, $w_2\left(\mathcal{r}\right)$, up to third order in the plasma parameter $\frac{q^2}{k_{\mathrm{B}}T}$. The $w_2\left(\mathcal{r}\right)$ short-range behavior appears to be an easily renormalizable quantity, while the long-range behavior confirms previous three-dimensional results.

The energy spectrum of elementary excitations in dilute ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures in investigated using a Feynman type of wave function. It is found that the ${\mathrm{He}}^3$ energy spectrum lies below the phonon-roton energy spectrum and exhibits a minimum near the roton minimum. Some consequences of this energy spectrum are discussed.

Series expansions for spin-spin correlations of simple-cubic, bcc, and square lattice Ising ferromagnets for general field and temperature have been analyzed. To within the attainable precision (of ± 1 to ± 5%) the exponents ${\nu }^{\prime }$ and ${\nu }^c$ are consistent with scaling predictions. Deviations of the scattering from Ornstein-Zernike forms are significantly larger quantitatively than above $T_c$; the second-moment correlation lengths verify $\frac{{{\xi }_1}^{+}}{{{\xi }_1}^{-}\mathrm{}\left(T\right)\mathrm{}}=1.96\mathrm{}\pm 0.03$ as $T\to {T_c}^{\pm }$.

We have observed the Raman scattering spectrum from finite crystals of MgO. Lines have been observed at 595, 719, and 1096 ${\mathrm{cm}}^{-1\mathrm{}}$. Very good agreement is obtained between the observed lines and the lattice dynamic theory of finite crystals. However, no agreement is obtained with the macroscopic theory.

Current-voltage characteristics of current-biased Josephson junctions with a phase-dependent dissipative current ${\sigma }_{1}Vcos\varphi$ have been calculated in the presence of thermal noise. Measurements on superconducting weak links indicate the existence of such a phase-dependent dissipative current of the same magnitude and sign observed in tunnel junctions.