A new thermal mode, fifth sound, has been observed in a superleak partially filled with superfluid helium. The velocity of the mode in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixtures is in good agreement with the theoretical value ${c_5}^2=\left(\frac{{\rho }_n}{\rho }\right){c_2}^2$. The index of refraction is found to be a strong function of the fractional filling of the superleak.

We report an observation of a superfluid helium-4 film sound mode consisting predominantly of a temperature wave, as in second sound, but with the normal-fluid component clamped. Our measurements indicate that this wave, called fifth sound, results in a contribution to the velocity of propagation which varies as $C_5={\left(\frac{{\rho }_n}{\rho }\right)}^{\frac{1}{2}}{C}_2$, as predicted by the two-fluid theory.

The results of an exhaustive high-precision heat-capacity study of the submonolayer regime of the krypton-graphite (Grafoil) adsorption system are presented. A phase diagram exhibiting a single two-phase coexistence region is proposed as an alternative to the previously proposed triple-point phase diagram. A quantitive correspondence between the locus of heat capacity anomalies in the Kr-graphite system and that for the ${\mathrm{N}}_2$-graphite system suggests the proposed phase diagram may apply to the ${\mathrm{N}}_2$ system as well.

The ordering temperature $T_c$ of the easy-plane antiferromagnet CsMn${\mathrm{F}}_3$ was measured as a function of magnetic field $H$. when H is perpendicular to the easy plane, $T_c$ decreases monotonically with increasing $H$, but the decrease is not proportional to $H^2$. The latter behavior is explained in terms of a virtual bicritical point which exists mathematically at a negative value of $H^2$.

Elastic scattering of 14.4 keV Mössbauer $\gamma$ rays from incommensurate ammonium fluoberyllate indicates that the distortion is essentially static and that phasons do not make anomalously large contributions to the Debye-Waller factor of satellite reflections.

The lifetime of the first excited torsional state of a hindered methyl group of $E$ proton-spin symmetry is found to be much less than the $A$-species lifetime. This is explained by a symmetric hindering potential, amplitude modulated by phonons, which also accounts for the observed widths of torsional ground-state tunneling transitions. The observations invalidate Allen's model for tunneling-splitting temperature dependence.

The magnetic relaxation of dilute Sm spins in Pr ethylsulphate has been measured by electron spin echoes. The Sm spins are relaxed by the fluctuating magnetic fields of the Pr spins which form $\mathrm{XY}$ chains. The measurements are in satisfactory agreement with the relaxation function calculated using the known spin correlation fractions for the $\mathrm{XY}$ model. As predicted for the $\mathrm{XY}$ model, spin diffusion is found to be absent or negligible.

Exact evaluation of low-order moments of the imaginary part of the dynamic susceptibility is used to analyze inelastic neutron scattering in a paramagnetic intermediate-valence system. It is shown that (i) the second moment of $\frac{{\chi }^{\prime \prime }(\overrightarrow{\mathrm{q}},\omega )}{\omega }$ measures the mixing energy, (ii) only a weak $\overrightarrow{\mathrm{q}}$ dependence of ${\chi }^{\prime \prime }(\overrightarrow{\mathrm{q}},\omega )$ is expected even in "coherent" systems, and (iii) there are no diffusive modes in the hydrodynamic regime.

Resonance enhanced inelastic light scattering from a quasi-two-dimensional electron gas confined at the interface of abruptly doped $\mathrm{GaAs}/n-{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ heterojunctions has been measured. The samples were fabricated using molecular-beam epitaxy with a high-contrast doping technique. The results show strong evidence for intersubband excitations in a two-dimensional electron system.

The dispersion relation for surface plasmons on a statistically slightly rough surface is shown to display a splitting under certain conditions. For a simple model of the correlation function of the surface roughness, explicit calculations are made which explain experimental results not previously interpreted.

Quantum stochasticity (the nature of wave functions and eigenvalues when the short-wave-limit Hamiltonian has stochastic trajectories) is studied for the two-dimensional Helmsholtz equation with "stadium" boundary. The eigenvalue separations have a Wigner distribution (characteristic of a random Hamiltonian), in contrast to the clustering found for a separable equation. The eigenfunctions exhibit a random pattern for the nodal curves, with isotropic distribution of local wave vectors.

Permutation symmetry is imposed on an $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\otimes \mathrm{U}\mathrm{}\left(1\right)\mathrm{}\otimes \mathrm{CP}$-invariant Lagrangian with six quarks. The mixing angles of the $b$ and $t$ are determined: $b$ decays predominantly to $u$ and a meson containing $b$ should have a lifetime ${\tau }_B\approx {10}^{-11\mathrm{}}$ sec or less. A phase in the gauge couplings of $b$ and $t$ causes nonconservation of $\mathrm{CP}$ in $K_L$ decays that is naturally small. No violations of $P$ and $T$ invariance are induced into the strong interactions by $\phi =\arg \left(\mathrm{Det}M\right)$ at the tree level. One-loop corrections yield an upper bound of $\phi <{10}^{-10\mathrm{}}\left(\frac{m_s}{m_b}\right){\left(\frac{m_t}{m_b}\right)}^2$.

It is shown that the path-integral measure for gauge-invariant fermion theories is not invariant under the ${\gamma }_5$ transformation and the Jacobian gives rise to an extra phase factor corresponding to the Adler-Bell-Jackiw anomaly. The derivation of "anomalous" Ward-Takahashi identities by means of the variational derivative can thus be made consistent in the path-integral formalism.

We have observed 217 (66) events of the process $\nu p\to \nu p$ ($\overline{\nu }p\to \overline{\nu }p$) with an estimated background of 82 (28). The neutral-to-charged-current ratios are $\frac{\sigma (\nu p\to \nu p)}{\sigma (\nu n\to {\mu }^{-}p)}=0.11\mathrm{}\pm 0.02$ and $\frac{\sigma (\overline{\nu }p\to \overline{\nu }p)}{\sigma (\overline{\nu }p\to {\mu }^{+}n)}=0.19\mathrm{}\pm 0.05$ for $0.40<\mathrm{}{Q}^2<0.90\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, where -$Q^2$ is the square of the momentum transfer to the nucleon. These yield $\frac{\sigma (\overline{\nu }p\to \overline{\nu }p)}{\sigma (\nu p\to \nu p)}=0.53\mathrm{}\pm 0.17$. The neutral-current form factors at $Q^2=0\mathrm{}$ are $G_E={0.5}_{-0.5\mathrm{}}^{+0.25\mathrm{}}$, $G_M={1.0}_{-0.04\mathrm{}}^{+0.35\mathrm{}}$, and $g_A={0.5}_{-0.15\mathrm{}}^{+0.2\mathrm{}}$.

This paper presents results from an experiment on the production of jets (groups of particles) with high $p_{\perp }$ produced in 200-GeV/c interactions. Results are presented on the comparison of jet cross sections on aluminum and hydrogen targets. The jet fragmentation distributions are also examined. Both the cross section and the jet structure are found to depend strongly on the beam and target types.

A theory for the intensities and shapes of fundamental band $R_1\mathrm{}\left(J\right)\mathrm{}$ and $P_1\mathrm{}\left(J\right)\mathrm{}$ lines of HD under pressures of rare gases is presented, with specific application to the $R_1\mathrm{}\left(1\right)\mathrm{}$ line of HD-Kr. The absorption contours principally consist of a broad (∼100 ${\mathrm{cm}}^{-1\mathrm{}}$) feature representing the ordinary intracollisional dipole intensity, and narrow components arising from the small HD permanent dipole moment function; permanent-dipole-collisionally-induced-dipole interference; and positive intercollisional interference between dipoles induced in successive collisions.

It is shown, via explicit solution of the Lorentz-Dirac equation to second order, that radiation reaction is responsible for increasing the asymptotic energy-momentum of a charged particle being swept over by an intense pulse of laser radiation. The amount of increase is dependent upon the total electromagnetic energy in the laser pulse per unit area of wave front.

I have measured the penetration length $\xi$ of a vortex into a subcritical region, using the electroconvective instability in a liquid crystal. $\xi$ corresponds to the correlation length of the order-parameter fluctuations in a second-order phase transition and is found to have a mean-field behavior. Moreover, I have found a new effect: propagation of solitary vortices over a distance equal to that correlation length.

Fast electrons produced by the irradiation of plane-layered targets with 20-J, 100-ps, ${10}^{15}$-W.${\mathrm{cm}}^{-2\mathrm{}}$, neodymium-laser pulses have been diagnosed by the $K\alpha$ emission which they cause at various depths in the targets. The fast-electron energy spectrum and absolute energy deposition (target preheat) are measured.

The quenching by an electric field of molecular-orientation fluctuations in freely suspended ferroelectric smectic-$C$ films has been studied by light scattering, allowing absolute measurements of polarization, elastic constants, and viscosities. Evidence is presented to demonstrate surface contributions to Frank elasticity and to show that Frank elasticity is nonlocal.