We report on a search for a short-lived neutral particle $\phi$ produced in the decay of the 9.17-MeV $J^{\pi }=2^{+}$ state in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$. The experiment is sensitive to decays into an $e^{+}{e}^{-}$ pair with ${\tau }_{\phi }\lesssim {10}^{-11\mathrm{}}$ s. For $m_{\phi }=1.7\mathrm{}$ MeV we place a limit on the branching ratio of $\frac{{\Gamma }_{\phi }}{{\Gamma }_{\gamma }}<~4\times {10}^{-4\mathrm{}}$ at the 90% confidence level.

A longitudinal-transverse separation has been carried out for the coincident quasifree proton knockout reaction on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in the range of three-momentum transfer 0.27-0.46 GeV/c. The deduced ratio of longitudinal and transverse response functions indicates a significant effect of the nuclear medium on the coupling of the virtual photon with the proton. The observed modification of this coupling implies a breakdown of the impulse approximation.

A high-resolution ($e,e^{\prime }p$) measurement has been performed to determine the relative occupation probability of the $3s_{\frac{1}{2}}$ proton orbits in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The knockout strength to the ground state of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ is 31(3)% smaller than that of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$. Appreciable fragmentation of $l=0\mathrm{}$ knockout strength is observed in ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$, whereas all $l=0\mathrm{}$ strength in the excitation range up to 5.5 MeV resides in the ground state of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$. Up to this energy the summed $3s$ strength is found to be 16(9)% smaller in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ than in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.

The suitability of the neutron multiplicity as a gauge for the violence of medium-energy heavy-ion reactions is investigated for the first time. For this purpose the number of neutrons emitted from fission reactions induced by 220-, 290-, and 400-MeV ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ on ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ is registered event by event with a large $4\pi$ scintillator tank. It is shown that the neutron multiplicity is indeed closely related to the two quantities characterizing the violence: the induced total intrinsic excitation and the linear momentum transfer.

The statistical role of the dinucleus as a "doorway" in heavy-ion deep-inelastic reactions is discussed. A detailed analysis of the reactions ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ + ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ at $120 \mathrm{MeV}<E_{\mathrm{lab}}<126.75\mathrm{} \mathrm{MeV}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at $30<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<42\mathrm{}$ MeV is presented. It is pointed out that the lifetime of the dinucleus extracted from excitation-function fluctuation analysis (Ericson fluctuation analysis) is close to that extracted from the final-fragment angular and charge distributions.

Quartet effects in deformed rare-earth nuclei are confronted from a phenomenological point of view. Some very simple systematic trends are evident in the experimental data when plotted as a function of a quartet number. The interacting-boson model has been modified to include quartet effects explicitly and it is able to reproduce accurately the experimental trends with fixed parameters.

A continuously tunable x-ray compensator that works in conjunction with synchrotron-radiation sources has been developed. The phenomena of polarization Pendellösung has been observed during its normal operation and the generation of circularly polarized x rays is verified through an observation of the magnetic Compton effect.

The evolution of turbulent plasmas is investigated within the framework of resistive magnetohydrodynamics. The functional form of the mean electric field is derived for fluctuations generated by tearing and resistive-interchange modes. It is shown that a bath of such local and global modes in pinches causes toroidal field reversal with finite pressure gradients in the plasma.

The rapid collapse of a sawtooth oscillation in the JET tokamak has been observed in detail on a fast time scale. Tomographic reconstruction of data from two x-ray cameras and electron-cyclotron-emission temperature profiles show that during the sawtooth collapse the central hot region is rapidly (in approximately 100 μs) displaced off axis with an $m=1\mathrm{}$ component and is then redistributed around a surface of constant minor radius. The theoretical implications of the measurements are discussed.

We show that the large curvature in the $T-P$ melting curve of KCl is the result of a reordering of the liquid to a more densely packed arrangement. As a result theories of melting, such as the instability model, which do not take into account the structure of the liquid fail to predict the correct pressure dependence of the melting curve.

We have used a vibrating-wire microbalance technique to investigate the wetting of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on solid surfaces. Although superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ wets solid substrates and forms a thick film, we find that films of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and normal ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are limited to less than thirteen layers. The $\lambda$ transition appears to be a wetting transition for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

From high-resolution measurements of the melting pressure of solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in applied fields, we determine the entropy and order of the magnetic phase transitions. We find the entropy discontinuity at the first-order antiferromagnetic transition to decrease as the field increases. No entropy discontinuity is seen at the paramagnetic to high-field transition, indicating that it is not first order.

Microscopic calculations of the dynamical properties of a fully polarized model Fermi liquid are presented and compared with those of an unpolarized model liquid. The model system is intended to simulate liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$.

The hypothesis that the properties of rare gases are well described by pair interactions together with long-ranged three-body interactions, in particular the Axilrod-Teller triple-dipole interaction, is tested for dense fluid krypton and xenon by Monte Carlo calculations. The agreement with experimental fluid properties found with use of the best available pair potentials with the Axilrod-Teller interaction is excellent. The net contribution of other many-body interactions to the properties of solid and dense fluid argon, krypton, and xenon must be very small.

U${\mathrm{Pt}}_3$ is a heavy-fermion superconductor with indications of coexisting long-range ferromagnetic spin fluctuations. Measurements of its specific heat at pressures of 0, 3.8, and 8.9 kbar between 0.35 and 20 K show that the spin-fluctuation terms are extremely sensitive to pressure: The linear term decreases by ∼ 25% at 8.9 kbar; the $T^3$ and $T^3\ln T$ terms decrease by factors of the order of 4. Comparison with the pressure dependence of the critical temperature suggests that the superconductivity is of a form that is enhanced by spin fluctuations.

The Josephson $I_c$ between a Ta-wire probe and an induced, surface, singlet, superconducting state in U${\mathrm{Be}}_{13}$ decreases with decreasing temperature below the bulk U${\mathrm{Be}}_{13}$ $T_c$, in contrast to the increase seen in comparison Mo samples. This shows that the bulk U${\mathrm{Be}}_{13}$ superconductivity suppresses the induced singlet superconductivity. Such suppression is evidence of a triplet super-conducting state in U${\mathrm{Be}}_{13}$. Evidence is presented for phase slip between weakly coupled singlet and triplet order parameters.

The behavior of quantum mechanical state functions under selective rotations is discussed. If a two-level transition is phase shifted with composite $z$ pulses, the component state function shared with a connected transition can be multiplied by $i$, thereby shifting the corresponding coherence into an orthogonal channel. Application to the sensitive indirect detection of NMR transitions is demonstrated.

Critical behavior of Ising spin-glass with $\pm J$ distribution is discussed. The results are based on the high-temperature series expansion of Edwards-Anderson susceptibility in powers of $w (=\frac{{tanh}^{2}J}{\mathrm{kT}})$ for 2D, 3D, and 4D "cubic" lattices to orders 19, 17, and 15, respectively. The lengths of the series are comparable to the best available for the pure Ising model. While 3D and 4D systems exhibit transitions at finite temperatures, in 2D a zero-temperature transition with a power-law divergence (in inverse temperature) for the susceptibility is found. The estimates of critical temperatures and exponents are presented.

We have found that a standard, widespread, chemical-preparation method for silicon, oxidation followed by an HF etch, results in a surface which from an electronic point of view is remarkably inactive. With preparation in this manner, the surface-recombination velocity on Si<111> is only 0.25 cm/sec, which is the lowest value ever reported for any semiconductor. Multiple-internal-reflection infrared spectroscopy shows that the surface appears to be covered by covalent Si-H bonds, leaving virtually no surface dangling bonds to act as recombinatiuon centers. These results have implications for the ultimate efficiency of silicon solar cells.

A model tight-binding Hamiltonian including off-diagonal disorder and Hartree-Fock electronic self-consistency is used to calculate the enthalpies of formation of the Mo-Cr, Mo-Nb, and Mo-Ta alloys. The approach combines the coherent-potential approximation, the generalized perturbation method, and the cluster-variation method. The model is also used to calculate the phase diagram and the equilibrium activities for the Mo-Cr system.