We show that in the reaction ${\pi }^{-}p\to {\pi }^{-}{\pi }^{-}{\pi }^{+}p$ at 3.9 GeV/c, the peaking in the ${\pi }^{-}{\pi }^{-}$ "scattering angular distribution" above 0.6-GeV c.m. energy inferred from the one-pion exchange model can be interpreted as resulting from a background of competing processes. Similar background effects may be significant also in the reaction ${\pi }^{+}p\to {\pi }^{+}{\pi }^{+}n$, and conclusions from that reaction as to evidence for $d$ waves in the $I=2\mathrm{}$ amplitude below 1 GeV should be reserved pending a similar analysis.

We consider a model of the weak interactions with scalar intermediate bosons $C^{\pm }$ with a negative metric in addition to the usual weak vector bosons $B^{\pm }$. With this modification, problems of divergence and high-energy behavior are greatly reduced. If the logarithmic weak and electromagnetic self-mass divergences are assumed to cancel each other, the coupling constant $g$ and the mass $m_B$ of the weak boson can be predicted.

The helicity density matrix for the process ${\pi }^{-}p\to {\pi }^{+}{\pi }^{-}n$ has been studied as a function of $M_{\pi \pi }$. The ratio $\frac{{{\rho }_{1-1}}^{\mathrm{hel}}}{{{\rho }_{11}}^{\mathrm{hel}}}$ shows no variation with $M_{\pi \pi }$ and it thus seems unlikely that the large discrepancy between the vector-dominance prediction and the observed asymmetry of single pions produced by linearly polarized photons could be the result of density-matrix distortion caused by background interference.

The extension of Veneziano's form $V(s, t)$ to the $N$-particle amplitude is given.

We present the most general parametrizations for the trajectory and residue functions for daughter Regge poles which are consistent with analyticity and unitarity. Our results are confined to the scattering of spinless particles, but are valid for arbitrary external masses and nonparallel trajectories. We show that except in the special case of pairwise-equal external masses, an infinite number of Lorentz poles contribute to the scattering amplitude at $s=0\mathrm{}$. We obtain a simple parametrization of the scattering amplitude for $s\sim 0$, $t\to \infty$, which involves powers of both $t$ and $\ln t$.

Optical pumping signals with Rb have been detected at temperatures ranging from 50 to 850°C. Spin-exchange signals have been detected with Ag (at 750°C), Li (at 400°C), and with electrons, hydrogen, and nitrogen over the entire temperature range. A preliminary value for the ${\mathrm{Li}}^6$ hfs separation is given.

The ground-state hyperfine structure interval $\Delta \nu$ of muonium has been remeasured with significantly improved accuracy through the observation of transitions between hfs states at low magnetic fields. The formation of muonium has been observed for the first time in krypton and the fractional pressure shift of $\Delta \nu$ has been measured in this gas. The average value of $\Delta \nu$ obtained from these measurements is $\Delta \nu =4463.26\mathrm{}\pm 0.04$ Mc/sec.

The Mössbauer spectra of ${\mathrm{Fe}}^{57}$, with the ${\mathrm{Co}}^{57}$ source in iron and palladium matrices, respectively, have been measured in a ${\mathrm{He}}^3$/${\mathrm{He}}^4$ dilution refrigerator. Both the magnitude and sign of the effective field at ${\mathrm{Co}}^{57}$ can be determined from nuclear polarization effects in the spectra, without recourse to an external magnetic field. Experimental data are also presented on the Kapitza thermal boundary resistance which, together with radioactive self-heating, prevents the source from cooling below 0.15°K.

We have measured by a new optical method the hypersonic attenuation in liquid ${\mathrm{He}}^4$ at a frequency of about 650 MHz. In this high-frequency range absorption data are presented between 1.2 and 4.2°K, including the vicinity of the $\lambda$ point. The results are compared with the previous low-frequency measurements.

We present a linked-cluster expansion for the ground state of a many-boson system which permits an exact treatment of particle conservation without introducing a chemical potential. We then propose a program of partial summations designed to permit accurate calculations with realistic He-He potentials. This theory treats the depletion effect in a fully consistent manner.

It is proposed that super water is a water composed of clusters having ice-II type hydrogen bonding whereas ordinary water has ice-I type hydrogen bonding. The properties of super water as compared with those of ordinary water can be explained on the basis that the more ordered structure of ice-II type clusters produces greater attractive forces between these clusters and less empty pockets in the resulting cluster aggregates.

We present new results that the states associated with Pb or Te vacancies in PbTe lie well up in the conduction band and that no localized states appear in the valence-conduction band gap. Holes and electrons due to Pb or Te vacancies cannot freeze out even at 0°K giving PbTe the character of a metal at very low temperatures.

Anomalies in the elastic constants and thermal expansion of vanadium single crystals in the range 180 to 260 K are reported and discussed in terms of a model of precipitation of hydrogen impurities. An extension of the impurity precipitation model is used to explain the appearance of sharp anomalies in the temperature dependence of the nuclear-acoustic-resonance linewidth in tantalum single crystals.

Radiative recombination in gold, copper, and gold-copper alloys has been observed arising from transitions between electrons in conduction-band states below the Fermi level and holes in the $d$ bands generated by optical excitation.

Very close to the superconducting transition temperature, the ratio of the critical magnetic field for surface superconductivity to the upper critical field for the vortex state, $\frac{H_{c3\mathrm{}}}{H_{c2\mathrm{}}}$, falls far below the Saint James-de Gennes factor of 1.7.

A previously unobserved splitting of the lowest exciton of LiBr is attributed to the exciton-phonon interaction in terms of a dynamical Jahn-Teller effect.

Stimulated Raman scattering from polaritons has been observed in LiNb${\mathrm{O}}_3$. The measured splitting of 134 ${\mathrm{cm}}^{-1\mathrm{}}$ between the 0° and 180° stimulated emission is in good agreement with infrared dispersion of the 628-${\mathrm{cm}}^{-1\mathrm{}}$ $A_1$ TO phonon. Threshold powers for the forward and backward stimulated emission are in fair agreement with the theory of polariton-stimulated Raman gain.

Measurements were made of the fission-neutron multiplicity associated with eleven ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ resonances in the energy range from 20 to 100 eV. It has been found that the multiplicity values are strongly correlated with the spins of the individual resonances and that the average multiplicity for the $J=0\mathrm{}$ group is 2.6% higher than for the $J=1\mathrm{}$ group.