The photoneutron cross section for ${\mathrm{He}}^4$ has been measured with monoenergetic photons from threshold to 31 MeV. The cross section reaches its maximum value of 1.0 mb from 24.3 to 27.3 MeV; the integrated cross section is 7.9 MeV mb. These are considerably lower than corresponding values for the ${\mathrm{He}}^4(\gamma ,p)$ reaction measured elsewhere.

The energy spectrum of 1.3 × ${10}^8$ $\alpha$ particles from the sequential decay ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}\left({\beta }^{-}\right){}_{}{}^{16}{}_{}{}^{}\mathrm{O}\left(\alpha \right){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been obtained. A group of 7100±1800 $\alpha$ particles with an energy of 1278±10 keV has been identified. They are attributed to the parity-forbidden decay from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ 8.87-MeV $2^{-}$ state into ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}+\alpha$. A width ${\Gamma }_{\alpha }=(1.8\mathrm{}\pm 0.8)\times {10}^{-10\mathrm{}}$ eV has been obtained for this transition.

Three levels have been observed above the neutron-decay threshold in ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$, at 11.01, 11.11, and 11.49 MeV; they undergo $\gamma$ decay exclusively to the 6.30-MeV $6^{+}$ state. Of these states the one at 11.01 MeV has $\gamma$-ray angular correlations in agreement with an $8^{+}$ spin and parity assignment, and that at 11.49 MeV with spin 7. The spin of the 11.11-MeV state is limited to 6 or 7.

$\gamma -\gamma \left(\theta \right)$ measurements with a NaI-Ge(Li) detector arrangement were carried out to measure the $M1\mathrm{}$ admixture in the 1183-keV, $2^{+}\to 2^{+}$ transition in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$. These results yield $M1=\left({85.6}_{-2.1\mathrm{}}^{+1.1\mathrm{}}\right)\%$ for the 1183-keV transition. Accurate branching ratios were also obtained from singles spectra taken with a large-volume Ge(Li) detector. It is possible to obtain from these intensities the same $Z_{\beta }$ value from the different branching ratios if a (73.0 ± 1.3)% $M1\mathrm{}$ admixture is assumed in the $2^{+}\to 2^{+}$ transition. Thus the measured $M1\mathrm{}$ admixture yields branching ratios that are not explained by the present band-mixing picture in contrast to earlier reports.

The spectrum of high-energy $\gamma$ rays following the absorption of negative pions in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been investigated. The observed shape of the spectrum and the measured total capture rate [(0.704±0.066) ×${10}^{15}$ ${\sec }^{-1\mathrm{}}$] agree well with theoretical predictions, assuming that the pions proceed through excitation of states in ${}_{}{}^4{}_{}{}^{}\mathrm{H}$ with $J^{\pi }=2^{-}$ at 3.4, $J^{\pi }=1^{-}$ at 5.1, and $J^{\pi }=1^{-}$ at 7.4 MeV relative to the ${}_{}{}^3{}_{}{}^{}\mathrm{H}+n$ threshold, and taking an operator $\approx {\tau }^{\mathrm{}(-)\mathrm{}}\sigma e^{i\overrightarrow{\mathrm{k}}·\overrightarrow{\mathrm{r}}}$ for the calculation of the nuclear-matrix elements.

High-energy capture $\gamma$ rays emitted from resonance neutron capture in ${\mathrm{U}}^{235}$ have been observed. In addition to known levels in ${\mathrm{U}}^{236}$ at 149 and 688 keV, six previously unobserved levels are populated, four of which appear to be members of the $\beta$ and $\gamma$ vibrational bands. Direct transitions from the capture state to spin-2 levels indicate that the 2.040- and 6.39-e V resonances have spin 3. The neutron separation energy of ${\mathrm{U}}^{236}$ is 6545±2 keV.

We have measured the differential cross section for the reaction $K^{+}n\to K^{0}p$ at 12 $\frac{\mathrm{GeV}}{c}$. We find that (1) the forward amplitude is essentially real, (2) the differential cross section equals that for the reaction $K^{-}p\to K^{0}n$, and (3) the differential cross section agrees well with the predictions of the Regge-pole model of Rarita and Schwarzschild. We have also compiled data on the cross section for the $K^{+}n$ charge-exchange reaction as a function of incident momentum, and compared it with that for $K^{+}p\to K^0{\Delta }^{++}$. We find that beyond threshold effects these two reactions have the same cross section.

A new partial-wave analysis is applied to the $3\pi$ decay of the ${A_2}^{-}$ in the reaction ${\pi }^{-}p\to p{\pi }^{+}{\pi }^{-}{\pi }^{-}$ at 5 and 7.5 $\frac{\mathrm{GeV}}{c}$. The relative importance of the spins and parities $0^{-}$, $1^{+}$, $1^{-}$, $2^{+}$, and $2^{-}$ are obtained as a function of $3\pi$ mass. Only the $2^{+}$ spin and parity shows resonant structure. Results are also given on the polarization and momentum-transfer dependence of the $A_2$ and on the mass dependence of the interference of $1^{+}$ background with $2^{+}$ resonance.

Consequences of the assumption that current commutators have power-type singularities near the light cone are derived. An extension of Wilson's short-distance expansion of commutators is suggested for almost lightlike distances. Consequences for power-type singularities are derived for processes involving currents. Especially, generalized scaling laws are obtained for inelastic electron-nucleon scattering. The connection with Regge behavior is discussed. An application to electron-positron annihilation into hadrons is also made.

We calculate the phase of vector-meson photoproduction on nuclei using the optical model. The predicted relative phase between ${\rho }^0$ and ${\omega }^0$ appears to disagree with experiment.

We report on our calculation of the energy and angular dependence of the cross sections for the production of various particles by two-photon annihilation processes in $e^{+}{e}^{-}$ and $e^{-}{e}^{-}$ colliding beams. For beam energy $E$ of more than 1 GeV, these cross sections [$\sigma \propto {\alpha }^4{\left(\ln E\right)}^3$] become increasingly more important than the usual one-photon cross sections [$\sigma \propto {\alpha }^2{\mathrm{}\left(E\right)\mathrm{}}^{-2\mathrm{}}$] for hadron production.

It is shown, on the basis of partial conservation of axial-vector current and current-algebra notions, how spectral-function information on the weak axial-vector current and isovector electromagnetic current can be extracted from soft-pion production in $e^{+}-e^{-}$ annihilations.

A model for the modulation of the methyl-group rotational tunneling frequency at low temperatures, which was previously introduced to account for proton spin-lattice relaxation, is here shown to predict hitherto unexpected features in methyl-group ESR hyperfine structure connected with the change with rising temperature from eight lines to four. Two experiments are described which confirm the predictions.

In ion drift velocity measurements, the spread in arrival time of the drifting ions has led to evaluation of a so-called longitudinal diffusion coefficient, $D_L$. It is shown that the spread in arrival times is attributable to the simple statistical fluctuation associated with addition of many nearly random free paths. On this basis, the value of $D_L$ derived from the data on the assumption that a true diffusion, dependent on an ion density gradient, is involved is shown to rise as the square of the drift velocity. Such a rise is observed experimentally, setting in when the drift velocity exceeds a minimum value. The real diffusion coefficient is then less than that reported as $D_L$.

A new linearized theory of the elastic and hydrodynamic properties of liquid crystals is presented. The theory requires neither a new state variable (the director) nor a new equation of motion for that variable. Instead, it relies exclusively on the standard conservation equations of mass, energy, and momentum. The foundation of the theory is the observation that the twisting and bending deformations of a liquid crystal are described by higher derivatives of the displacement than those which occur in the usual shear elastic energy of a crystal. Normal isotropic fluid behavior occurs only when both of these elastic energies vanish. The theory leads to quantitative relations between measured elastic and viscous parameters and measured light-scattering linewidths.

For several years, we have been empirically producing steady-state, mirror-confined hot-ion plasmas with $T_i\approx \mathrm{a}$ few keV and $n_i\approx \frac{{10}^{13}}{{\mathrm{cm}}^3}$. We describe here the ion-heating mechanism, which is an instability having a fine-grained azimuthal structure covering a broad band of frequencies around ${\omega }_{\mathrm{pi}}$, having a rapid growth rate on the order of ${\omega }_{\mathrm{pi}}$, and being driven by an intense radial dc electric field. It does not require that $T_e>T_i$.

Collisionless modes extracting electron thermal energy and convecting it radially are considered as a possible explanation of the electron thermal energy radial transport, larger than the one predicted by the proper collisional theory, in confined high-temperature plasmas carrying a current along the magnetic field.

A value for $\frac{2e}{h}$ has been determined by the ac Josephson effect using niobium point-contact junctions. The value with respect to the international voltage standard as maintained at the Bureau International des Poids et Mesures, Sèvres (${\mathrm{V}}_{\mathrm{BIP}\mathrm{M}69\mathrm{}}$), is $\frac{2e}{h}=483.593\mathrm{}84\pm 0.00010$ MHz/μV.

Radiophosphorus diffusion in (111) silicon, under intrinsic conditions from an oxide source in air and from doped silicon sources (epitaxial, polycrystalline, and vapor phase) in a hydrogen atmosphere, has conclusively demonstrated the pronounced effects of both the free surface and the redox reaction on the apparent phosphorus diffusivity in silicon.

The anharmonic interactions between librational waves in solid hydrogen are found to lead to significant perturbations in the single-libron spectrum. This large anharmonicity is also responsible for two-libron processes whose frequencies and Raman intensities are calculated. Our results for the one- and two-libron spectra are in excellent agreement with, and hence explain, the optical data.