We have observed changes in the drift properties of negative ions in liquid helium when they are exposed to near-infrared radiation. The existence of this effect strongly supports the bubble model of the ion's structure. The results imply a bubble radius of 21.2±0.5 Å and a well depth of 1.0±0.2 eV.

The temperature and volume dependence of the Helmholtz free energy ($A$) of metallic sodium has been calculated in a semitheoretical fashion with an estimate of anharmonic effects included in the calculation. The thermodynamic properties predicted by the theoretical equation of state agree quite well with the experimental data.

A proof is given that the expectation value of the Heisenberg exchange Hamiltonian for ferromagnetism can be computed exactly, knowing only the spectral function for the transverse correlation functions. The proof is readily extended to Ising and Dyson theories of magnetism, and to ferrimagnets of $n$ sublattices. Application to calculations of magnon specific heats shows that special care is required when approximate magnon spectra are used to evaluate the exact relation.

The differential elastic-scattering cross sections of 1-BeV protons on hydrogen, helium, carbon, and oxygen have been measured. The nuclear data exhibit diffractionlike structure associated with the multiple scattering of protons by nucleons inside the nuclei. The experimental technique provides a new and powerful method for studying nucleon-nucleon correlations inside the nucleus.

Simultaneous observations of low-energy (∼0.5 MeV) protons emitted in a solar flare of 7 July 1966 were made with detectors on board the earth satellites Explorer 33 and Injun IV, located outside and inside the earth's magnetosphere, respectively. We find that such protons have full and essentially immediate access from interplanetary space to the polar caps of the earth.

Three structures are observed in $\overline{p}-p$ and $\overline{p}-d$ total cross sections in a transmission experiment. Two structures, at center-of-mass energies 2190±5 and 2345±10 MeV respectively, are found in the isospin-one state. The third structure, at 2380±10 MeV, is found in the isospin-zero state.

A method is sketched for writing down invariant amplitudes which give the leading contributions of families of Regge trajectories of definite O(4) class (at zero momentum transfer). The method is illustrated by the case $\pi +N\to \rho +N$, where it leads to definite predictions (in spite of unequal masses) for the leading term in each helicity amplitude.

The $K^{+}$ and $K^{-}$ decay rates into the $\tau$ and $K_{\mu 2}$ modes have been compared in an experiment at the Brookhaven alternating-gradient synchrotron. The results are $\frac{\Gamma (K^{+}\to {\pi }^{+}+{\pi }^{+}+{\pi }^{-})}{\Gamma (K^{-}\to {\pi }^{-}+{\pi }^{-}+{\pi }^{+})}-1=-0.0004\mathrm{}\pm 0.0021$ and $\frac{\Gamma (K^{+}\to {\mu }^{+}+{\nu }_{\mu })}{\Gamma (K^{-}\to {\mu }^{-}+{\overline{\nu }}_{\mu })}-1=-0.0054\mathrm{}\pm 0.0041$. The absolute decay rate for $\tau$ was found to be (4.496±0.030) × ${10}^6$ ${\sec }^{-1\mathrm{}}$.

It is shown that fixed poles in the $l$ plane are forbidden for strong interactions unless there exist moving branch points with very specific properties. A fixed pole with protective cuts is considered as a possible model for diffraction scattering.

It is shown that the second-order radiative corrections to ${\pi }^{\pm }\beta$ decay are finite, provided one assumes a $V-A$ interaction and a current algebra constructed from spin-½ SU(3) triplet fields with the quantum numbers of $\Lambda$, ${\Xi }^0$, and ${\Xi }^{-}$, or ${\Omega }^{-}$, ${\Xi }^0$, and ${\Xi }^{-}$, and $\frac{1}{3}$-integral hypercharge; or, equivalently, $V+A$ together with $p$, $n$, $\Lambda$ or $p$, $n$, ${\Omega }^{\prime +}$ triplets.

The ${\left[\mathrm{SU}\mathrm{}\right(3)\mathrm{}\otimes \mathrm{SU}\mathrm{}(3\left)\right]}_{\beta }$ algebra of factorized Regge-pole residues is applied to obtain relations between meson-baryon and baryon-baryon exchange processes. This theory reproduces results previously obtained only in the "quark model" and gives new relations as well.

It is shown that the corrections due to octet mass splitting and finiteness of the parity-nonconserving spurion lead to significantly better agreement of the prediction with experiments for the eight independent nonleptonic hyperon-decay amplitudes. Comments are made on the reasons for the validity of Lee-Sugawara sum rules for the parity-non-conserving and parity-conserving decays.