The nuclear magnetic susceptibility of pure solid ${\mathrm{He}}^3$ (1×${10}^{-5\mathrm{}}$ ${\mathrm{He}}^4$ impurity) at molar volumes of 23.3, 23.6, and 24.2 ${\mathrm{cm}}^3$/mole has been measured between 0.2 and 0.04°K. Antiferromagnetic nuclear ordering is indicated with the Néel temperature $T_{\mathrm{N}}$ increasing from (0.75±1)×${10}^{-3\mathrm{}}$°K at 23.3 ${\mathrm{cm}}^3$/mole to (2.4±1)×${10}^{-3\mathrm{}}$°K at 24.2 ${\mathrm{cm}}^3$/mole. Special attention has been given to thermal equilibrium.

The dimensions of the electronic lattice structure of the hexagonal quartz crystal and the fcc Ca${\mathrm{F}}_2$ crystal have been measured by resolving characteristic markings on the angular-correlation curves as observed for the two gamma quanta emitted in the annihilation of positrons with electrons in these crystals.

We show that the intensity of x-ray and neutron scattering by anharmonic crystals is markedly affected by the interference between one- and multiphonon scattering processes. The previously unexplained intensity modulation in the x-ray diffuse scattering from NaCl is shown by calculations to be largely of this origin. We have also observed the effect of the interference in neutron inelastic scattering from KBr; calculations give quantitative agreement with the experimental results.

The absorption structure of sodium metals has been measured in the vicinity of the onset of $2p$ electron absorption. The results agree with theoretical investigations which claim a sharp absorption peak at the edge.

Photoemission measurements with photon energies ranging from the onset of Na $2p$ electron absorption to 50 eV have been performed using synchrotron radiation as a light source. The results indicate that the rise in the absorption coefficient starting at about 8.5 eV above the onset of $2p$ electron transitions is due to continuum transitions, whereas in the region below, most of the structures turn out to be exciton excitations.

Neutron-diffraction studies have shown that ferromagnetic MnP undergoes a transformation to a periodic fan structure by an external magnetic field. The magnetic moment in the fan is higher than that in the ferromagnetic state. Both the moment and the period of the fan decrease with increasing applied field.

It is shown how a comparison of the $\gamma$ widths for corresponding $T=\frac{3}{2}\to T=\frac{1}{2}$ transitions in mirror nuclei can give information about a possible isotensor component of the electromagnetic interaction. From data available at present it is concluded that the isotensor $\gamma$ transition amplitude in the decays considered is less than about 10% of the isovector amplitude.

Proton angular distributions have been measured for the reactions ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(\alpha , p){}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}(\alpha , p){}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(\alpha , p){}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ at $E_{\alpha }=30\mathrm{}$ MeV. Strong $J$ dependence is observed for the $l=1\mathrm{}$ transfer distributions to the ground and first excited states of ${}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$ and ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$, whereas essentially no $J$ dependence is observed for the $l=2\mathrm{}$ transfer distributions to the first and second excited states of ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$. Distorted-wave Born-approximation calculations are also discussed.

The cross section for photoproduction of ${\pi }^0$ mesons was measured at a photon energy of 3 GeV and squared four-momentum transfer ($t$) of -0.1 to -1.2 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ using plane-polarized photons. The asymmetry was found to be consistent with +1.0 for $t$ values above -0.4 and below -1.1. For $-0.4\mathrm{}<~t<~-1.0\mathrm{}$ there is a dip in the asymmetry and at $t=-0.6\mathrm{}$ it drops to 0.55 ± 0.15. This result precludes a simple Regge model with ${\omega }^0$ and $B$; a theoretical description requires Regge cuts or an ${\omega }^{\prime }$ exchange.

Neutron-proton charge-exchange differential cross sections for incident-neutron momenta between 600 and 2000 MeV/c show a sharp change in the slope of $\frac{d\sigma }{\mathrm{dt}}$ vs -$u$ in the vicinity of $-u=0.01\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. Near the one-pion threshold the slope at $u=0\mathrm{}$ shows a maximum which reaches a value of order 100 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$. Also presented, as a function of $s$, is the intercept at $u=0\mathrm{}$ which shows a pronounced deviation from smoothness in the region above the inelastic threshold.

A model for particle scattering amplitudes is based on the harmonic-oscillator Green's function. The model is Regge behaved, and in first approximation is a zero-width theory. The derived amplitudes are very similar to Veneziano $n$-point functions although they lack duality.

The Treiman-Yang analysis is extended to test the validity of the O(3,1) expansion of a two-body scattering amplitude and related to the $M$ value of a Toller pole.

The scalar, pseudoscalar, vector, and axial-vector form factors of the pion are derived from (i) the Veneziano amplitudes for ${\pi }^{+}{\pi }^{-}\to {\pi }^{+}{\pi }^{-}$ and ${\pi }^{+}{\pi }^{-}\to {A_1}^{+}{\pi }^{-}$. (ii) the hypothesis of the partially conserved axial-vector current, and (iii) the requirement that a chirally conjugate pair of form factors should exhibit similar structures. The resulting form factors feature an infinite sequence of poles corresponding to daughters of specific spin and parity, and definite signature. Various predictions on the clashing-beam production of $2\pi$ and on $\rho$-meson coupling constants are given.

Vector-meson dominance predicts a characteristic energy dependence of incoherent $\rho$ photoproduction from complex nuclei. Measurements of this process were made which do not conform to these predictions.

A method for applying many-body perturbation theory to molecules is discussed. The energy of ${\mathrm{H}}_2$ is calculated to be -1.176 a.u. Results are also given for the static dipole polarizability.

A modified fast-passage transition scheme, using two frequencies, is described and discussed.

We have measured the temperature dependence of the dynamic proton polarization in a 0.2-g sample of 95% 1-butanol and 5% water, containing 0.75% of the free radical porphyrexide, between 1.4 and 0.5 K. The largest polarization attained was 67% at 0.5 K. The feasibility of achieving comparable polarization in larger samples and the question of the origin of the observed temperature dependence are discussed.

The scintillation of liquid helium produced by $\alpha$ particles has been measured with particular emphasis on the temperature region below 1.25°K which had not been studied previously. An interpretation of the observed inhibition of the scintillation below $T_{\lambda }$ is proposed which attributes the effect to a reduced radiative destruction rate of metastable states in He II.

We present high-precision data for $C_p$ near $T_{\lambda }$ and give three interpretations in terms of scaling predictions. We find no interpretation fully in agreement with the predicted symmetry of the transition and a divergent $C_p$.

In thin films and granular superconductors, the quantization of the phonon wave vector delimits the phonons which can be emitted in a recombination process. We predict jumps in lifetimes for injected quasiparticles and the disappearance of some emitted phonons at characteristic values of $\frac{\Delta }{\mathrm{kT}}$.