The consequences of mixing between SU(4) multiplets of the same $J$, $P$, and $C$ are examined. Within the proposed theoretical framework, the presently available data indicate that there should be substantial mixing between the pseudoscalar multiplets ($P$ and $P^{\prime }$) while the vector multiples ($V$ and $V^{\prime }$ containing $\psi$ and ${\psi }^{\prime }$) remain largely unmixed. The ratio $\frac{F_P}{F_{P^{\prime }}}\sim 2$ of the pseudoscalar decay constant leads to the suppression of the decays $\psi \to {\eta }_c\gamma$ and ${\psi }^{\prime }\to {\eta }_c\gamma$.

It is proposed that the leading Regge trajectory on which $q_i{\overline{q}}_j$ mesons ($i,j=u,d,s,c\dots$) lie satisfies the equation ${\alpha }_{\mathrm{ij}}\mathrm{}\left(t\right)=a+\alpha _{\mathrm{ij}}^{}{}_{}{}^{\prime }\mathrm{}(t-b)\mathrm{}$ with ${\left(\alpha _{\mathrm{ij}}^{}{}_{}{}^{\prime }\right)}^2=\alpha _{\mathrm{ii}}^{}{}_{}{}^{\prime }\alpha _{\mathrm{jj}}^{}{}_{}{}^{\prime }$. The latter is justified with use of the factorization property of Regge poles. $\frac{J}{\psi }$-like states associated with still heavier quarks are predicted to be not narrow if their mass exceeds 5.6 GeV.

The recoil-induced spectral doubling of the C${\mathrm{H}}_4$ saturated absorption peaks at 3.39 μm has been clearly resolved. A working resolving power of 8 × ${10}^{10}$ (1 kHz half width at half-maximum), achieved with aberration-compensated parabolic optics of 32 cm diam, was available to study the height ratio and splitting of the recoil peaks. The resolved Dopplergenerated level crossings are not recoil doubled and give improved hfs information. We derive new, exact equations relating the atomic natural frequency to laboratory resonance frequencies.

The strong-signal regime of a free-electron laser is analyzed in terms of a set of "generalized Bloch equations." We show that for current free-electron-laser configurations the saturation will be reached for a field on the order of ${10}^7$ V/m, with an efficiency at saturation of 5×${10}^{-3\mathrm{}}$. However, a strong reshaping of the electron distribution may alter the efficiency of free-electron lasers in cases where the electron beam is recycled from one shot to the next.

The low-frequency density fluctuations observed in an ohmically heated toroidal plasma are found to be consistent with a spectrum of electrostatic drift modes which can account for the measured anomalous particle loss rate.

The intensity of 10.6-μm radiation scattered from carbon plasmas has been measured as a function of incidence and collection angles (with angular resolution $<~1.3°$), and of laser mode structure. Over an incident intensity range ${10}^{11}$-${10}^{13}$ W ${\mathrm{cm}}^{-2\mathrm{}}$, total reflectivity was typically ≲ 8%. At certain angles, reflectivity often showed 100% temporal modulation. The relevance of these results to critical-surface and stimulated-scattering phenomena is discussed.

A theoretical description is given of the polarization charge-density distribution induced in a solid by the passage of a fast charged particle. The stopping power of the solid (including the effects of close collisions) is well accounted for by the braking effect of the polarization charges. Calculations based on this model for the polarization give good agreement with the results of recent experiments on the dissociation of fast molecular ions in foils.

Energy-loss experiments with 50-keV electrons on thin polycrystalline films of Al and In yielded data for the surface plasmon dispersion up to $k_{\parallel }=0.47\mathrm{} \mathrm{and} 0.42$ ${\mathrm{\AA }}^{-1\mathrm{}}$, respectively. The wave-vector dependence of the surface plasmon frequency of Al shows a significant increase for $k_{\parallel }>0.3\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$, while in the case of In there is only a weak increase for $k_{\parallel }>0.2\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$.

We report on the first observation of a Raman echo, using spin-flip Raman scattering at 4905 Å of bound donors in CdS to create a coherent spin state. The free-induction decays associated with each pulse in the sequence of two $\frac{\pi }{2}$ pulses as well as the echo are probed by spin-flip Raman scattering at 4880 Å.

The transition from transient trap-controlled hopping among traps has been observed in a polymer matrix doped with two transport molecules of different ionization potential. The nonequilibrium properties of the transport, characteristic of the disordered molecular state, are manifested by an apparent concentration-dependent trap depth.

The path integral of quantum gravity probes space-times with nontrivial topology and induces chiral symmetry breaking via an anomaly proportional to ${\epsilon }^{\mu \nu \rho \sigma }R_{}^{\alpha }{}_{\beta \mu \nu }{}^{}R_{}^{\beta }{}_{\alpha \rho \sigma }{}^{}$ in the divergence of the axial fermion number current. The corresponding classical instanton solution of Einstein's equations with cosmological term is found. The Euler-Poincaré characteristic and ordinary instanton number are also discussed.

The $(2\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{},F=0)$-$(2\mathrm{}{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{},F=1)$ interval in atomic hydrogen has been measured in zero magnetic field by scanning a radio-frequency perturbation through the atomic resonance. The measured interval was found to be 909.904 ± 0.020 MHz, which is consistent with that reported by Lundeen and Pipkin, 909.940 ± 0.020 MHz. Our deduced value of the Lamb shift 1057.862 ± 0.020 MHz is in good agreement with Mohr's calculated value 1057.864 ± 0.014 MHz but not with Erickson's value of 1057.912 ± 0.011 MHz.

We report on a new type of high-energy electron-proton scattering experiment in which longitudinally polarized electrons are scattered from longitudinally polarized protons. The asymmetry in elastic scattering at $Q^2=0.765\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ was measured; our result agrees with the theoretical asymmetry and determines the sign of $\frac{G_E}{G_M}$ to be positive.

We report measurements of the asymmetry in deep inelastic scattering of longitudinally polarized electrons by longitudinally polarized protons. The antiparallel-parallel asymmetries are positive and large in agreement with predictions of quark-parton models of the proton. A limit is obtained on parity nonconservation in the scattering of longitudinally polarized electrons by unpolarized nucleons.

Spectrographic observation of a population inversion between the levels $n=3\mathrm{}$ and $n=2\mathrm{}$ in a rapidly expanding C VI plasma is reported. These and other results are shown to be in good agreement with a computer model, which is used to predict the conditions required to obtain laser action at 182 Å.

An expression for the spectral distribution of drift-wave fluctuations is obtained from a new mode-coupling equation that describes the superposition of drift-wave normal modes induced by the divergence of the nonlinear $\overrightarrow{E}\times \overrightarrow{B}$ convective flux. Computations for the adiabatic toroidal compressor experiment indicate that the observed spectrum is consistent with the theoretical spectrum.

Global excitation of Alfvén waves in the Proto-Cleo $l=3\mathrm{}$ stellarator was accomplished by exciting a helical winding corresponding to a $q=3\mathrm{}$ rational surface with a pulsed, high-power rf source. A doubling of both the electron and ion temperatures was observed, and a slight increase in the ratio of the temperatures with and without rf heating occurred at the predicted resonance locations. Enhanced loss also occurred during heating, with 2.5-kHz oscillations observable in a microwave interferometer signal after heating.

Inelastic neutron scattering and measurement of the ortho-para separation coefficient have been used to study the low lying rotational states of molecular hydrogen adsorbed on activated alumina. The observations are consistent with a picture in which the orientational motion of the molecules is severely hindered. Results are analyzed in terms of two models: a two-dimensional rotor and an axially constrained rotor. The latter which is more consistent with the data serves to explain preferential adsorption of orthohydrogen.

The collective modes of the gap parameter for the axial (Anderson-Brinkman-Morel) state and their coupling to the quasiparticles are studied in the collisionless regime within a microscopic theory. In addition to the modes connected with the spontaneous breakdown of symmetries (sound, spin waves, and orbit waves), three weakly damped modes with a typical dispersion law ${\omega }^2\mathrm{}\left(q\right)={\omega }^2\mathrm{}\left(0\right)+\alpha {\left(v_{\mathrm{F}}q\right)}^2$ are found. The feasibility of detecting these modes in the sound absorption is discussed.

Substrate core chemical shifts upon chemisorption of oxygen on aluminum are observed using variable-excitation-energy photoelectron spectroscopy. At low exposures a unique intermediate oxidation state evolves where the $\mathrm{Al} 2p$ level is shifted by only 1.3 eV toward higher binding energy as compared to the 2.6-eV shift observed for heavily oxidized aluminum (${\mathrm{A}1\mathrm{}}_2$ ${\mathrm{O}}_3$). Simultaneous observation of the $\mathrm{O} 2p$ resonance shows evidence for a sharp phase change at exposures close to monolayer formation.