Interaction of 10.1- and $15.8-\frac{\mathrm{GeV}}{c}$ positive and negative muons with nuclear emulsion nuclei is studied for events with one gray or black prong in addition to the outgoing muon track. The events involving very low energy exchange are consistent with "giant dipole" resonance. The line shape, its width, and the cross section of this resonance is discussed, as well as the angular distribution of the low-energy protons.

We report a high-statistics measurement of the neutron-proton charge-exchange differential cross section for incident momenta 3 to $12 \frac{\mathrm{GeV}}{c}$, and four-momentum transfers 0.003 to $0.85 {\left(\frac{\mathrm{GeV}}{c}\right)}^2$. The data are normalized absolutely to ±20%. The differential cross section is characterized by a sharp peak at small momentum transfers, with a gentler exponential behavior at large momentum transfers. This shape is remarkably independent of the incident momentum.

We have studied the reaction $e^{-}+p\to e^{-}+{\pi }^{+}+n$ by detecting the final electron and pion in coincidence. Data are presented in the region of virtual photon mass squared from -0.18 to -1.2 Ge${\mathrm{V}}^2$, and virtual photoproduction center-of-mass energy and angle from 1.85 to 2.50 GeV and 0 to 20°, respectively.

New data on forward ${\pi }^{+}$ electroproduction are in reasonable agreement with the predictions of a dispersion-theory calculation by Berends. This model is used to extract the pion electromagnetic form factor. The result is consistent with $F_{\pi }={F_1}^V$, but a simple $\rho$-pole form factor cannot be ruled out.

The reaction $\gamma p\to {\rho }^{-} {\Delta }^{++}$ was studied between 4 and 8 GeV using positron-annihilation radiation. Assuming $\sigma \propto {E_{\gamma }}^{-a}$ we find that $a=0.6\mathrm{}\pm 0.2$. With sufficiently large absorption corrections, a one-pion—exchange model can fit this dependence, but requires a width for $\rho \to \pi \gamma$ much in excess of the value predicted by SU(3).

It is shown that the $\Delta Q=2\mathrm{}$ semileptonic process can be tested by experiments on muonic atoms. The $\Delta$ resonances in nuclear ground states will lead to a ${\mu }^{-}\to e^{+}$ reaction presently observable if the $\Delta Q=2\mathrm{}$, $\Delta S=0\mathrm{}$ interaction is within about two orders of magnitude of the ordinary strangeness-conserving interactions. The consequences for various lepton schemes is discussed.

A technique is presented for determining average radiative lifetimes of multiply charged heavy ions which are predominantly excited in collisions with light gas atoms. The method utilizes the measurement of ionic charge-state distributions as a function of target density. Average lifetimes ranging from more than 65 to 0.76 nsec have been determined for chlorine ions with charge states + 1 to + 6, respectively.

Two ionic neutralization reactions have been studied with a mass spectrometer and with a planar rf-conductivity probe in the decay of a dilute thermal plasma at 300°K produced by megavolt-electron bombardment of ${\mathrm{N}}_2$:${\mathrm{O}}_2$ mixtures at 2 to 22 Torr. For N${\mathrm{O}}^{+}$ + N$\mathrm{O}_2^{}{}_{}{}^{-}$ recombination we obtain a rate coefficient of (1.75 ± 0.6) × ${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$/sec, and for N${\mathrm{O}}^{+}$ + N$\mathrm{O}_3^{}{}_{}{}^{-}$ recombination, (3.4 ± 1.2) × ${10}^{-8\mathrm{}}$ ${\mathrm{cm}}^3$/sec.

The ground-state energy of a charged-boson gas at high density is re-examined and it is found that Brueckner's exact result for the second-order energy is reproduced precisely by Feenberg's variation-perturbation method.

Measurements of the positive-ion velocity as a function of electric field in dilute solutions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at 18 mK show a discontinuity which suggests the existence of two kinds of vortex rings in addition to the bare ion. The assignment of circulation quantum numbers is discussed.

Upon application of a sufficiently strong transverse magnetic field, the low-temperature thermopowers of both aluminum and indium change sign from negative to positive. In aluminum the change in sign is produced by a change in sign of the "electron-diffusion" component. In both metals the magnitude of the "phonon-drag" component is increased.

Below the Curie temperature, with increasing magnetic order, Eu-rich EuO shows both a change of 0.15 mm/sec in the ${\mathrm{Eu}}^{151}$ isomer shift and an insulator-metal transition with a resistivity change of more than 13 orders of magnitude. These effects are interpreted on the basis of an exchange-induced configurational change (autoionization) of two electrons trapped at an oxygen vacancy.

We report observation of efficient stimulated emission (gain ∼ ${10}^4$ ${\mathrm{cm}}^{-1\mathrm{}}$) from recombination of excitonic molecules. This emission is obtained near 3.16 eV (3920 Å) in optically excited CuCl crystals and shown to be stimulated by use of a recently described technique employing a variable excitation length. These results in CuCl point out the importance of excitonic molecules in intrinsic stimulated-emission processes in semiconductors.

Using giant quantum oscillations in the attenuation of ultrasound, we have observed nonextremal areas of the electron Fermi surface of bismuth. The giant oscillations occur simultaneously with oscillations due to extremal areas, and both the periods and the general shape of these oscillations can be explained by the theory of Gurevich, Skobov, and Firsov.

We present experimental evidence confirming the existence of the theoretically proposed double-plasmon-excitation process in solid-state plasmas. Preliminary measurements of the relative probability of single- and double-plasmon excitation in aluminum show good agreement with theory.

Simultaneous measurements of damping and elastic modulus of copper as affected by electron irradiation have been made. These data do not follow the standard analysis, using the Granato-Lücke theory for damping, in which point defects, created by irradiation, are presumed to act as firm pinning points on dislocation lines. It is proposed instead that these defects are dragged along by the dislocation line moving under oscillating stress. This dragging can lead to an observed "anomalous" peak (initial increase and subsequent decrease) in the decrement as a function of electron dose.

The two-proton-transfer reactions ${}_{}{}^{44,48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{46,50}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{48,50}{}_{}{}^{}\mathrm{Ti}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{50,52}{}_{}{}^{}\mathrm{Cr}$ studied at 48-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ incident energy show that the first excited states must include strong proton-pair components. It appears that the (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$) two-proton-transfer reaction is a new and useful spectroscopic tool.

We develop a projection-operator theory of photodisintegration. It is shown that the coupling of 3p-3h (three-particle, three-hole) modes to the 1p-1h modes can explain the intermediate structure of the giant resonance in oxygen when the 1p-1h states are treated as "doorways" for $\gamma$-ray absorption and for particle emission. The structure problem is treated using the interacting-boson approximation of Iachello and Feshbach.

Using a number of realistic, local and nonlocal, separable two-nucleon interactions, it is shown that threshold $s$-wave pion production is sensitive to the $D$-state probability of the deuteron and the nonlocality of the interaction. This enables one to use the reaction $p+p\to {\pi }^{+}+d$ to study the relative strength of the central to tensor potential and the nonlocality of the nucleon-nucleon interaction at short distances.

Evidence for a broad resonance in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ system has been found in the excitation function for the radiative capture of deuterons by protons. Supporting evidence is provided by the behavior of the angular distributions. The resonance is centered at (19.5±0.5)-MeV excitation, has a width of about 2 MeV, and is most likely characterized by $(L^{\pi },S,T)=(1^{-},\frac{1}{2},\frac{1}{2})$.