We construct and study six— and eight—charged-pion amplitudes. Factorization properties of the parent $\pi$ trajectory show the $\pi$ and $A_1$ to be simple and the $\pi \left(2^{-}\right)$ to be a double state reminiscent of the $A_2$ doubling.

It is shown that the connected scattering amplitude for three free particles may be written (as the three-body energy $E$ goes to zero) in the form $A{E}^{-1\mathrm{}}+B{E}^{\frac{-1\mathrm{}}{2}}+C\ln E+O\left(1\right)\mathrm{}$ with $A$, $B$, and $C$ completely determined by kinematics and the two-body scattering amplitudes at zero energy.

A general expression is derived for the electric field gradient resulting from the overlap distortion of cation $p$ orbitals by the surrounding ligands. This contribution can be larger than that arising from point charges and electric dipoles in the lattice. The inclusion of overlap distortion in the determination of the nuclear quadrupole moment $Q$ of ${\mathrm{Al}}^{27}$ in ${\mathrm{Al}}_2$${\mathrm{O}}_3$ reduces $Q$ from 0.377 to 0.155 b. The latter value is in good agreement with 0.149 b obtained from atomic-beam experiments.

We observe the temperature dependence of the alignment of an isomeric state in ${}_{}{}^{73}{}_{}{}^{}\mathrm{As}$ (426 keV, ${\frac{9}{2}}^{+}$, $\tau =8\mathrm{} \mu sec$), produced by the reaction ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}\mathrm{}(d,n)\mathrm{}{}_{}{}^{73}{}_{}{}^{}\mathrm{As}$ in solid Ge. The relaxation process can be interpreted with a diffusion-controlled time-dependent quadrupole interaction due to radiation-induced lattice damage. A diffusion energy of $E=1.3\mathrm{}\pm 0.2$ eV is assigned to the activation energy for excess vacancy diffusion. This result yields, for the first time, quantitative insight into relaxation mechanisms associated with radiation damage in solids, which may occur when implantation techniques and nuclear reactions are employed.

The magnetic field dependence of the fusion rate between inequivalent triplet excitons (free and trapped triplets in tetracene-doped anthracene crystals) is qualitatively different from that between equivalent excitons. Additional high-field level-crossing resonances and a new low-field dip appear in delayed fluorescence at room temperature.

The frequency-dependent susceptibility has been obtained for the pseudospin-phonon system previously considered by Kobayashi. Various limiting cases are discussed and connection is made with the dielectric properties of K${\mathrm{H}}_2$P${\mathrm{O}}_4$.

An extension of the simple linear combination of atomic orbitals and molecular orbitals model of electronic structure in transition-metal compounds can explain the apparent discrepancy between the neutron magnetic scattering results in antiferromagnetic ${\mathrm{Ni}}^{+2\mathrm{}}$ and ${\mathrm{Mn}}^{+2\mathrm{}}$ salts. Using a slightly extended multicenter basis, we have obtained variational restricted and unrestricted Hartree-Fock wave functions for the ${\left(\mathrm{N}\mathrm{i}{\mathrm{F}}_6\right)}^{-4\mathrm{}}$ and ${\left(\mathrm{M}\mathrm{n}{\mathrm{F}}_6\right)}^{-4\mathrm{}}$ clusters which exhibit bonding and spin-polarization effects which differentiate the reductions in the forward scattering amplitudes. These functions simultaneously explain the anisotropic hyperfine parameters observed for the two ions in KMg${\mathrm{F}}_3$.

In a time-of-flight study of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ photoneutrons in which neutron energy spectra were obtained at different bremsstrahlung end-point energies between 15.5 and 29.5 MeV, de-excitation neutrons from excited states of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ were observed.

We report measurements of the "spin-spin effect" in the neutron total cross section of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ employing a polarized ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ target.

A method of continuing the two-nucleon transition matrix off the energy shell for bound-state, partial-wave eigenchannels is presented. The arbitrary parmeters of this method are a symmetric function of momentum ${\sigma }_W(k,k^{\prime })$ and the bound-state wave function ${\Psi }_B\mathrm{}\left(r\right)\mathrm{}$. The phase-shifts are essentially contained in ${\sigma }_W\mathrm{}(k,k)\mathrm{}$. While a potential is presumed to be present, it never explicitly appears in determining the $T$ matrix.

The multideterminant nuclear wave function has been used to derive a system of coupled equations for the particle orbitals and the configuration-mixing coefficients to be solved self-consistently by iterations. To illustrate the procedure ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ has been considered. Compared with the Hartree-Fock solution the results show many significant differences and are energetically more favorable.

Striking similarities are found in the proton momentum spectra involving pion and kaon production processes. Except for the falloff near the kinematical limits, the longitudinal-momentum distributions are isotropic. In the transverse-momentum spectra, a sharp break near ${P_{\perp }}^2=0.2\mathrm{} {\left(\frac{\mathrm{GeV}}{c}\right)}^2$ is observed in both processes. The breaks are attributed to the production and decay of peripherally produced nucleon resonances.

An experiment on electroproduction of muon pairs with invariant masses between 400 and 900 MeV is reported. The experiment, interpreted as a text of the timelike photon propagator, shows agreement with QED. Photon propagator modifications representing (+) metric and (-) metric heavy photons are limited to masses $\Lambda >1260\mathrm{}$ and $\Lambda >750\mathrm{}$ MeV, respectively (15 times the mass limits of positronium experiments). A model used to calculate $\rho -\mathrm{Q}\mathrm{E}\mathrm{D}$ interference yields a best $\rho -\mathrm{Q}\mathrm{E}\mathrm{D}$ phase angle of 16°±22°.

We have determined the cross section for the process ${\mathrm{Na}}^{+}+{\mathrm{O}}^{-}\to \mathrm{Na}\mathrm{}\left(3p\right)+\mathrm{O}$ as a function of relative kinetic energy in the range 0.06-7 eV. The measurements were achieved by monitoring the intensity of the $\mathrm{N}\mathrm{a}-D$ doublet at 5890 Å emitted from the collision region of a merged-ion-beam device. The cross section is extremely large, ${10}^{-12\mathrm{}}$-${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^2$, and shows at least one sharp peak, at 2.75 eV.

An intense optical pulse at 10.6 μm, of rise time that is short compared with the inverse bandwidth of an active C${\mathrm{O}}_2$ medium in which it is amplified, has been observed experimentally to attain a sharpened leading edge and attenuated lagging edge. This is an effect attendant upon optical nutation in the C${\mathrm{O}}_2$ medium. Computer solutions are presented for comparison.

The quantum mechanical description of parametric fluorescence is the splitting of a single photon into two photons. This description has been verified by observing coincidences between photons emitted by an ammonium dihydrogen phosphate crystal pumped by a 325-nm He-Cd laser. The coincidence rate $R_C$ decreases to the calculated accidental rate [$<0.03\mathrm{}{R}_C\left(max\right)$], unless the two detectors are arranged to satisfy energy and momentum conservation and have equal time delays.

Electric-dipole-excited conduction-electron spin resonance has been observed for the first time in the far infrared in the II-VI semiconductor ${\mathrm{Hg}}_{1-x}{\mathrm{Cd}}_x\mathrm{Te}$. Circular polarization and intensity studies as a function of magnetic field unambiguously identify this transition. Electron $g$ values are obtained for the $L=0\mathrm{}$ Landau level at several magnetic fields.

The ${\mathrm{N}}^{14}$ NMR spectrum in the nematic phase and linewidth in the isotropic phase of para-azoxyanisole (PAA) are reported. The linewidth $\Delta$ in the isotropic phase follows the relation ${\Delta }^{\propto }{(T-T^{*})}^{\frac{1}{2}}$, where $T^{*}$ is a temperature slightly below the nematic-isotropic transition. This result is interpreted in terms of the local order fluctuations expected in the vicinity of a weakly first-order transition.

Comparison of the Mössbauer isomer shift of dilute ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ in ${\mathrm{V}}_2$${\mathrm{O}}_3$ with that obtained in chromium-doped insulating ${\mathrm{V}}_2$${\mathrm{O}}_3$ shows that the high-temperature anomaly represents a gradual return from the metallic to the insulating state. The implications of this conclusion on the interpretation of the thermal expansion, susceptibility, and transport properties are pointed out.

The thermodynamic functions of dilute ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ solutions are expressed in terms of the excess molar volume in a model-independent fashion. In this way the effective ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ quasi-particle potential is found, without the assumption of Bardeen, Baym, and Pines. We find that the term $-\frac{{\alpha }^2{m}_4{s}^2}{n_{40}}$ in the effective potential is completely cancelled, but that new terms of another form appear.