Based on the dual amplitude analysis of the "ditriple" Regge limits in inclusive hadronic reactions, the general properties of the Reggeon-Reggeon amplitude are conjectured and a duality sum rule is suggested. From this sum rule, predictions are made on the two-Reggeon-particle and triple-Reggeon couplings for diffraction dissociations.

A partial solution to the muon puzzle is offered. Discrete scale transformations are used to derive a mass spectrum for leptons which includes all the observed leptons. The difference between the electron and muonlike particles is demonstrated explicitly. Experimental tests of the theory are discussed including the detection of the predicted 22-GeV electron.

The assertion in a recent Letter, stating the nonequivalence of the Kemmer and the Klein-Gordon spin-0 wave functions in the analysis of $K_{l3\mathrm{}}$ decays, is shown to be incorrect.

We prove that the asymptotic vanishing of the longitudinal part of the total virtual photoabsorption cross section on protons implies the vanishing of the wave-function renormalization constant $Z_2$. Present data indicate that $Z_2\lesssim 0.1$ (consistent with zero) suggesting that the proton is indeed a composite particle.

From data on muon pairs and by use of the hypotheses of conservation of vector current and scale invariance, we estimate the cross section for production of weak vector mesons $W^{\pm }$ at energies pertinent to Brookhaven National Laboratory, the CERN intersecting storage rings, and the National Accelerator Laboratory. With existing data, these estimates imply a lower limit of 4.5 GeV/${\mathit{c}}^2$ for the $W^{\pm }$ mass.

Photon echo and optical nutation have been easily observed in ${\mathrm{C}}^{13}$${\mathrm{H}}_3$F and N${\mathrm{H}}_2$D by applying Stark pulses which shift the molecular levels into resonance with cw laser radiation. Numerical computations of the nutation effect agree with observation, and echo characteristics closely follow predictions of existing theories. The $T_2^{}{}_{}{}^{\prime }$ pressure dependence, from infrared-echo measurements, indicates that ${\mathrm{C}}^{13}$${\mathrm{H}}_3$F relaxes primarily by rotational energy transfer.

The molecular treatment of the reaction $p+\mathrm{H}\mathrm{}\left(1s\right)\mathrm{}\to p+\mathrm{H}\mathrm{}\left(2p\right)\mathrm{}$ has been reexamined. Exact ${\mathrm{H}}_2^{+}$ wave functions and dynamic coupling elements have been calculated and used throughout. Two- and four-state calculations have been carried out in the range 0.1-16 keV and compared with previous theoretical and experimental findings. The results support the validity of the molecular approach at higher velocities than previously considered. A new basis set, rather than translational factors, eliminates spurious asymptotic radial coupling inherent in the Born-Oppenheimer basis.

Electron-paramagnetic-resonance spectra of ${\mathrm{Nd}}^{+3\mathrm{}}$ ions in the $f^3$, ${}_{}{}^4{}_{}{}^{}I_{\frac{13}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}I_{\frac{15}{2}}^{}{}_{}{}^{}$ excited states were observed at ∼1.5°K in a single-crystal La${\mathrm{Cl}}_3$ host. Values of the spin-Hamiltonian parameters which describe the spectra of the even-nuclear-spin species and of the ${}_{}{}^{145}{}_{}{}^{}\mathrm{Nd}_{}^{+3\mathrm{}}{}_{}{}^{}$ ion were determined. The excited states of ${\mathrm{Nd}}^{+3\mathrm{}}$ were populated by energy transfer from photoexcited ${\mathrm{U}}^{+3\mathrm{}}$ ions incorporated in the same crystal.

The magnetic field dependence of the longitudinal nuclear-spin relaxation time for ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ nuclei in paramagnetic GdP is shown to yield the Fourier transform of the sum of two electronic-spin correlation functions. This represents a new experimental technique for the study of paramagnetic spin dynamics. A reasonable fit to a theoretical spectrum is achieved, and the resulting exchange strength agrees with that deduced from the Curie-Weiss temperature.

Parametric excitation of ion waves is invoked to explain the efficient interaction between electromagnetic waves and the ionosphere.

${\mathrm{He}}^3$ and ${\mathrm{He}}^4$ monolayers on graphite at coverages $0.45<~x<~0.61$ show strong heat-capacity peaks near 3°K. Temperature dependences and densities indicate that both isotopes undergo second-order transitions from the two-dimensional gas state to a regular lattice in registry with the substrate structure.

The effects in spin-echo experiments predicted by Leggett and Rice for Fermi liquids in large magnetic fields and at low temperatures have been verified for liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. A preliminary value of the Fermi-liquid parameter $\frac{Z_1}{4}$ determined from this work is 0 ± 0.3 for the liquid at saturated vapor pressure.

We attribute the formation of a shoulder in the high-frequency ultrasonic attenuation in superfluid helium under pressure to a restriction on the three-phonon process with thermal phonons. The restriction is proposed to follow from the pressure dependence of the phonon dispersion at zero temperature. The steep rise above the shoulder due to phonon-roton and roton-roton interactions also indicates large dispersion effects under pressure.

It is shown that the third frequency moment of the dynamic density-density correlation function ${\chi }^{\prime \prime }(k,\omega )$ diverges for quantum and classical systems with hard-core potentials. Some information is obtained about the leading term of the divergence in the hard-core limit.

A model is proposed to account for the increased plasticity found for superconductors entering the superconducting state. It is supposed that at low enough temperatures in superconductors, inertial effects permit dislocations to overshoot their static equilibrium positions against obstacles and exert greater forces on the barriers. Quantitative agreement is found with experimental results for the temperature dependence of the stress drop. There is evidence that inertial effects contribute to the flow stress of nonsuperconductors.

Pb-GaAs Schottky barriers irradiated progressively by 10-MeV electrons or fast neutrons were found to exhibit anomalous behavior identical to that produced by varying the initial doping. The results are consistent with the Hubbard model of the Mott transition.

Absorption of phonons by stress-split acceptor states in germanium has been observed. A distinction is found between the "static" ($a^{*}q\ll 1$) and "dynamic" ($a^{*}q\gtrsim 1$) deformation potential constant ($a^{*}$ is the effective Bohr radius of impurity; $q$ is the wave number of relevant wave component), thus resolving an apparent conflict in previous reports. The effect of phonon scattering by isotopic impurities and of resonant phonon absorption results in phonon propagation in a well-defined frequency interval (phonon "window").

We report observations in diamond of buildup of acoustic phonons well out in the Brillouin zone. The acoustic phonon generation accompanies strong pumping by harmonic $k\approx 0$ optical phonons. Phonons are detected by their effect on impurity fluorescence. The Orbach phonon breakdown mechanism is calculated to play an important role.

We show that in the long-wavelength region the magnetoelastic effect allows both the free-lattice and the frozen-lattice mode to exist in the heavy rare earths Tb and Dy. The former may be more easily detected by ferromagnetic resonance at low frequencies and low temperatures, and the latter predominates at high frequencies and high temperatures.

Our results experimentally confirm free-lattice-model behavior in Tb at low microwave frequencies, as predicted by Vigren and Liu. The resonances below a temperature of 140 K were only observable when the external magnetic field was not precisely aligned along an $a$ axis in the hexagonal plane of the sample.