The dynamic collective model has been extended to quadrupole giant resonances in spherical nuclei. The splitting of giant dipole and giant quadrupole resonances due to their coupling to surface vibrations has been calculated for Sn isotopes. Agreement with recent $\gamma$-absorption measurements of the Livermore group has been found.

Emission of singlet deuterons was observed in the reaction ${\mathrm{B}}^{10}({\mathrm{He}}^3,d ){\mathrm{C}}^{11}$ by studying neutron-proton correlations. The resulting angular distributions are very similar to those of triplet deuterons and can be described in distorted-wave Born approximation assuming the $d$ to behave like a single particle.

The charge-exchange reaction $\mathrm{pp}\to n{\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ has been systematically analyzed up to 24.2 GeV/c to test the concept of dominance in the $t$ channel by high-lying Regge trajectories at very high energies. The results provide clear evidence for no more than pion exchange up to the highest momentum studied.

The form of the pairwise nonadditive three-body dispersion potential for asymmetric molecules is derived. It is found that molecular asymmetry can have a large influence on interactions of this type. An example indicating the possible use of these results in understanding cohesive energies in crystals is given.

Coherence transfer between atomic levels requires the matching of the Larmor frequencies. For levels with different $g$ factors this occurs only in zero magnetic field. By changing the $g$ factors through coupling with a nonresonant rf field, one can match the Larmor frequencies and make the transfer possible in nonzero magnetic fields. Resonances in the transfer appear, depending on the rf field amplitude. ${\mathrm{Rb}}^{87}$-${\mathrm{Cs}}^{133}$ spin-exchange experiments are reported which provide an illustration of the theory.

The nuclear magnetic resonances of ${\mathrm{Eu}}^{151}$ and ${\mathrm{Eu}}^{153}$ have been studied in single crystals of europium iron garnet with externally applied fields of sufficient magnitude to align the magnetization along various crystallographic directions. Hyperfine-field and quadrupole-splitting parameters are obtained. Contributions to the electric field gradients and anisotropic hyperfine fields are discussed and compared with theory.

Mössbauer spectra of magnetically dilute hemin solutions have been observed. These are found to be consistent with infrared measurements and with Mössbauer measurements of crystalline hemin. This confirms Blume's interpretation of the Mössbauer spectrum in terms of spin-spin relaxation.

Averaging effects produced by relaxation have been observed for Sr${\mathrm{Cl}}_2$: ${\mathrm{La}}^{2+}$, a system exhibiting the dynamic Jahn-Teller effect. Observed temperature and sample dependences are consequences of a rapid direct relaxation process between the vibronic components of the ${}_{}{}^2{}_{}{}^{}E$ ground state. This interpretation is consistent with similar effects seen for ${\mathrm{Cu}}^{2+}$, ${\mathrm{Sc}}^{2+}$, and ${\mathrm{Eu}}^{2+}$ in cubic crystals.

Computer experiments have been carried out on the anomalous heating of a one-dimensional plasma by a large-amplitude long-wavelength electric field oscillating near the plasma frequency. Above a certain threshold the large driver field excites an instability in the plasma and drives up ion-density fluctuations as well as plasma oscillations. When the ion fluctuations reach a sufficiently large level, the plasma begins to heat very efficiently according to an anomalous resistivity. An effective collision frequency as high as $0.2{\omega }_{\mathrm{pe}}$ has been observed. A theoretical explanation of the observed results is given.

A one-dimensional sheet-charge model is used to simulate homogeneous conterstreaming plasmas with no magnetic field. We demonstrate that the only electrostatic instability capable of dissipating a substantial fraction of the relative ion-drift energy and thus generating a turbulent, collisionless shock is the ion-ion two-stream instability. Furthermore, it is shown that such a shock cannot occur at high Mach numbers.

We present time-resolved spectra of electrostatic turbulence in the earth's bow-shock structure. Spectral details on scales for a few Debye lengths indicate that single modes or groups of single modes dominate the turbulent spectrum. These modes are probably ion-acoustic or Buneman instabilities of short wavelength ($k{\lambda }_{\mathrm{D}}\sim 1$) which are generated in parts of the shock microstructure containing diamagnetic drift currents.

An evolution from the linear growth to the nonlinear saturated state of instability is investigated by observing the spatially growing ionization waves (moving striations) in a plasma. The behavior of the instability is shown to obey the Landau amplitude equation. Partial, gradual change in zeroth-order conditions by the nonlinear effect is also found.

Spectral measurements have been made of $L$-shell x rays produced by 50- to 330-keV Ar ions incident on Ar gas targets. The data are considered within the framework of the level-crossing model of Fano and Lichten, and the observed lines are consistent with Hartree-Slater calculations for highly excited configurations.

A theoretical formula is derived for the free induction decay of a spin-½ system on the basis of the Kubo-Tomita theory of magnetic resonance. This formula is used to make clear the approximate nature of the Lowe-Norberg and Clough-McDonald theory. Good agreement is found between theory and experiment for the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ free induction decay in a single crystal of Ca${\mathrm{F}}_2$.

Photocount fluctuation problems, treated previously for Gaussian statistics only, or in the limit of short measurement times, have been extended to arbitrary times (compared with the intensity correlation time) and to general Markoffian processes. In particular, we calculate the distribution function of the time-integrated light intensity for a laser operated near threshold.

The calculations of Eilenberger and Büttner are misleading in the regime where $\lambda$ and $\xi$ are complex. We study the regime of validity of linear-response theory in calculating the asymptotic properties of plane boundary and vortex structure. On this basis, it is not possible to predict if a sufficiently clean low-$\kappa$ type-II superconductor such as niobium or vanadium will exhibit field reversal at low temperatures.

Measurements of the wavelength derivative of the indirect absorption edge in Si show features associated with the creation of free excitons in states $n=1\mathrm{} \mathrm{and} 2$ as well as in the exciton continuum. The spectrum shows no valley-orbit splitting of the excitons, contrary to previous suggestions, and it is shown theoretically that such splitting of free excitons cannot exist. It is found also that previous determinations of the energies of higher exciton states ($n>\mathrm{}1\mathrm{}$) were in error. Finally, LO phonon participation has been identified for the first time in the indirect edge of Si.

A search for coincidences between cosmic-ray shower signals in a large scintillation counter and gravitational-radiation detector signals indicates that the gravitational radiation detector does not produce a signal when hit by showers of particle density of the order of 100 particles/${\mathrm{m}}^2$.

Strong ${\pi }^0$, ${\eta }^0$, and ${\omega }^0$ peaks have been observed in the reaction $p+d\to {\mathrm{He}}^3+\mathrm{missing}\mathrm{mass}$ at incident proton momenta of 3.5-3.8 GeV/c and proton-to-meson momentum transfer $t=-1.5\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The mesons are produced with center-of-mass cross sections on the order of ${10}^{-34\mathrm{}}$ ${\mathrm{cm}}^2$/sr at a center-of-mass angle of about 60°. The missing-mass spectrometer combined the "Jacobian peak" and the orthogonal dispersion techniques.

The differential cross section for the reaction $\gamma +n\to {\pi }^{-}+p$ was measured for laboratory photon energies between 600 and 1250 MeV, using a liquid deuterium target. The internal nucleon momentum distribution of the deuteron was used to calculate the major effect of using deuterium as a neutron target. The data show that the amplitude to excite the $F_{15}\mathrm{}\left(1688\right)\mathrm{}$ resonance is small, in agreement with a recent quark-model prediction.