The superfluid density in small pores filled with He II has been measured using fourth sound. When the onset temperature for superfluidity is below $T_{\lambda }$, it is found that the fractional superfluid density is much reduced compared to that of the bulk helium.

Measurements have been made of the fractional density of superfluid, $\frac{{\rho }_s}{\rho }$, in helium II contained in micropores (average radius ∼31 Å), as calculated from fourth-sound measurements between 1.2 and 2°K. Since the lambda transition is greatly modified in this system, the temperature variation of $\frac{{\rho }_s}{\rho }$ may generally be expected to differ from that in "infinite" bulk liquid, at least near the transition temperature. The results lead to the conclusion that the critical velocity in such channels decreases rapidly with increasing temperature above 1.2°K.

Two separate pulse-light sources, the first capable of producing singlets from which triplets are obtained by intersystem crossing, the second producing primarily a photon flux, have been used to produce a photocurrent in anthracene. An enhanced photocurrent is produced by the second flash well after the first flash has terminated. The decay of this effect appears to be characteristic of the lifetime of the triplets. The enhanced photoconductivity is believed to be a result of a tandem excitation process involving the triplets as the intermediate state.

Surface plasma oscillations at optical frequencies have been detected by their radiation from an optical grating surface permitting a measurement of their dispersion relation.

The dispersion of plasma-wave propagation in the alkali metals sodium and potassium has been observed to deviate significantly from that expected for a noninteracting electron gas. Modifications of the dispersion have been calculated using the Landau Fermi-liquid theory and a quantitative evaluation of the first two moments of the interaction function has been made for the case of potassium.

Time-reversal invariance has been tested via detailed balance in the compound-nuclear reactions ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}+\alpha \rightleftarrows {}_{}{}^{27}{}_{}{}^{}\mathrm{Al}+p$. The relative differential cross sections agree within the experimental uncertainties, leading to an estimated upper limit for the ratio of the $T$-nonconserving to the $T$-conserving reaction amplitudes of (2-4)×${10}^{-3\mathrm{}}$. The same upper limit is found for the nuclear matrix elements which are odd with respect to time reversal.

Results are presented for the binding energy of ${\mathrm{H}}^3$ and the doublet $n-d$ scattering length ($a_{\frac{1}{2}}$) using a rank-four separable potential which simulates the hard core as well as the tensor force. The binding energy is nearly four times the deuteron binding energy, and $a_{\frac{1}{2}}$ is 0.13-0.18 F for the best available ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ potentials, in close agreement with the latest experimental value.

Viscosity due to the long mean free paths of electron neutrinos in the primordial fireball just before $e-{\nu }_e$ scattering stops at ${10}^{10}$°K reduces any homogeneous anisotropy in the expansion of the universe to a level which does not effect the expansion rate significantly thereafter.

Saturating a Weinberg-type sum rule for the spectral functions entering the propagators of the isovector and the hypercharge currents [which follows from asymptotic SU(3)] by the $\rho$, the $\omega$, and the $\varphi$, we obtain $\Gamma (\varphi \to K\overline{K})=3.1\mathrm{}$ MeV.

A sum rule of the scalar and pseudoscalar spectral functions is studied as a possible test for the commutation relations between the fourth component of the axial-vector current and the scalar and pseudoscalar densities. Approximating the spectral functions by the one-pion and two-pion contributions, one finds the sum rule to be badly violated.