The reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(\alpha ,2\mathrm{}\alpha )d$ was studied at 50.4, 59.0, 60.5, 70.3 and 79.6 MeV. The angular distributions and energy dependence of the off-energy-shell $\alpha -\alpha$ cross section were extracted and compared with those for free $\alpha -\alpha$ scattering. The agreement between the two is excellent, as predicted by the peripheral model in the quasifree approximation, but the quasifree approximation is not precise enough.

The interplanetary negatron and positron spectra from 12 to 220 MeV have been determined with a balloon-borne magnetic spectrometer. The observed charge ratio $\frac{e^{+}}{(e^{+}+e^{-})}\approx 0.3$ indicates that the flux most likely consists of a mixture of "primary" negatrons and interstellar "secondary" negatrons and positrons. We deduce an absolute solar modulation of the interstellar positron flux which decreases with decreasing magnetic rigidity below about 80 MV.

We show that radio emission from a neutron star with a magnetic field of ${10}^9$ G or more can account for the radio emission of pulsars. It is suggested that pulsars also emit two bands, one in the uv or optical, and the other in the infrared in the decamicron wavelength range.

A method of forming a compressed electron ring for an electron ring accelerator in a static rather than pulsed magnetic field is proposed. Advantages of this method as well as some problems and possible solutions are discussed and results of computer studies are presented.

We have measured the bremsstrahlung yield at 6.2° in the reaction $e^{-}+\mathrm{C}\to e^{-}+\mathrm{C}+\gamma$ using incident-electron energies up to 9.5 GeV. The data confirm the predictions of quantum electrodynamics for timelike electron four-momenta up to 1 GeV.

The validity of vector-meson dominance is tested by comparing our high statistics ${\rho }^0$ and $\omega$ production experiments at 2.7 and 4 GeV/c with the results of polarized photopion production experiments. Our results suggest the breakdown of the vector-dominance model even after taking into account the strong $S$-wave $\pi \pi$ interaction in the ${\rho }^0$ region.

Data are presented showing that the $Y_1^{}{}_{}{}^{*}\mathrm{}\left(1385\right)\mathrm{}$ production angular distribution in the reaction ${\pi }^{-}p\to Y^{*-}{K}^{+}$ and in its charge-symmetric counterpart ${\pi }^{+}n\left(p_{\mathrm{sp}}\right)\to Y^{*+}{K}^0\left(p_{\mathrm{sp}}\right)$ is characterized by peripheral ($\hat{N}·{\hat{Y}}^{*}\approx +1\mathrm{}$) and antiperipheral peaking. Explanation for the latter is sought in terms of baryon exchange; so comparisons with other $\pi N\to Y^{*}K$ reactions are made. The peripheral peak cannot arise through the exchange of any known meson. Alternative explanations are considered.

The angular distribution of deuteron photodisintegration has been measured at laboratory photon energies from 240 to 320 MeV in a spark chamber experiment at the Cornell 2-GeV synchrotron. The angular dependence of the cross section is consistent with other recent measurements. A comparison with data on the inverse reaction, $n+p\to d+\gamma$, should provide a meaningful test of time-reversal invariance in electromagnetic interactions of hadrons.

The reactions ${\pi }^{-}+p\to {\pi }^{-}+X+p$, $X\to {\pi }^{+}+{\pi }^{-}$, for incident ${\pi }^{-}$ energy of 25 BeV, has been analyzed within the framework of the multi-Regge exchange model.

An unambiguous formulation is presented for the derivation of the two-pion as well as one-boson exchange contributions to the nucleon-nucleon potential. It contains no internal momentum expansions, and depends only on experimentally determined coupling and mass parameters. The calculated result, containing terms linear in the momentum operator, is remarkably close to the Hamada-Johnston potential for distances $r\gtrsim 0.7$ F.

We present data for signals associated with the crossing of fine structure levels of a hydrogenlike atom when these levels are excited at a uniform rate and coupled by the application of a static electric field. With modest electric field strengths, strong crossing signals are seen even when the lowest order of coupling for the two levels involved is third order.

Metastable argon atoms are found to be forward scattered along with ground-state atoms after ${\mathrm{Ar}}^{+}$ + Ar charge-transferring collisions. Using a detection technique involving Penning ionization of acetylene, it was found that the cross section for metastable excitation has a magnitude of the order of ${10}^{-3\mathrm{}}$ ${\mathrm{\AA }}^2$ and exhibits two distinct low-energy resonances as a function of incident ${\mathrm{Ar}}^{+}$ energy.

Pulsed electron-nuclear double-resonance effects in phosphorus-doped silicon were studied by monitoring the electron spin echo arising from the donor electron. The application of a four-pulse sequence of EPR and NMR pulses was found to produce a periodic attenuation and restoration of the electron spin echo as the carrier frequency of the rf pulses was swept. This phenomenon is explained by considering the $z$ component of the local field produced at the donor electron by surrounding shells of distant ${\mathrm{Si}}^{29}$ nuclei.

We describe the technique and features of electron-nuclear double-resonance-style resonance measurements in alkali halide $F$ centers using optical pumping and optical monitoring detection of the resonance. Greater sensitivity, ability to see low-field resonances, and greater simplicity in choosing desirable fields and frequencies are the main features of the technique.

Equilibrium and nonequilibrium charge-state distributions have been obtained for high-energy ions emerging from crystals. In a major channeling direction in silicon, the slower ions and those incident in low charge states emerge nearly at equilibrium, with a mean charge close to that in a random direction. High-energy channeled oxygen $8^{+}$ ions emerge far from equilibrium, indicating a capture cross section of less than 2× ${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$.

The atomic flux resulting from cesium-ion recombination on the hot end plates of a $Q$ device has been measured. The rate of ion loss to the end plates is found to be only a small fraction of the total loss rate, if the plasma potential is negative.

A free-fall theory is developed for the decay of the average electron number density and of the electron temperature in a pulsed cylindrical mercury vapor discharge plasma using moment equations for the ions with a collision term for momentum loss, and assuming Maxwellian electrons. The plasma assumption was used. Good agreement is obtained with experimental results on four tubes of varying diameter.

The results of measurements of third-sound velocity in adsorbed superfluid helium films (1.12-1.85°K) are presented. It is found that the average superfluid fraction is nonvanishing at the superflow onset thickness and has a value about $\frac{3}{8}$ its bulk value. Possible reasons for a nonvanishing value are discussed. Healing lengths based on best fitting Ginzburg-Pitaevskii calculations are determined.

Consistent with theoretical predictions, the triplet-exciton-diffusion tensor is found to be strongly anisotropic in anthracene crystals at room temperature. Triplet migration in anthracene is essentially two-dimensional, restricted to the $\mathrm{ab}$ plane.

A formal theory for the investigation of crystal surfaces by the scattering of particles is developed. Expressions satisfying the condition of unitarity are presented for diffraction as well as one-phonon inelastic scattering, including the effects of surface bound states. The possibility of detection of surface phonons by scattering of low-energy He atoms from a cleaved surface is investigated.