Chromic methylammonium alum and manganous ammonium sulfate have been used in complementary experiments to establish a paramagnetic salt temperature scale ($T_M$) from 0.9 to 18 K which is based on the N.B.S.-1955 platinum resistance thermometer scale. The liquid-helium vapor-pressure scales differ from $T_M$ almost linearly in temperature up to 4 K with a maximum deviation $T_M-T_{58}=6.7\mathrm{}$ mK at 4.2 K. Satisfactory agreement is found between $T_M$ and an earlier constant-volume gas thermometer scale. $T_M$ and the N.B.S. acoustic scale differ systematically by 0.03% from 2.2 to 19 K with a maximum deviation of 5 mK from a linear relation.

NMR measurements (±5%) of self-diffusion in xenon to within 10 ppm of the critical temperature show no anomaly relative to the behavior on the liquid branch of the coexistence curve between 177 and 281°K. In this lower temperature range we observe $\rho D\propto T^{2.74\pm 0.08}$. This same temperature dependence also describes similar data of Trappeniers and Oosting for the nearly spherical molecule methane.

Experimental values for the elastic constants of hcp ${\mathrm{He}}^4$ are derived from longitudinal sound velocities and the compressibility. The derivation makes use of a relation between the elastic constants which is a consequence of the volume independence of the axis ratio of hcp ${\mathrm{He}}^4$. Good agreement exists between the elastic and calorimetric Debye temperature.

A theory of ion-wave instabilities is presented which takes into account the self-consistent inhomogeneities generated by currents flowing along magnetic field lines. It is found that for $T_e\sim T_i$, the minimum unstable current is reduced from the electron to approximately the ion thermal speed. The result is attributed to the drift-wave instability caused by the inhomogeneities produced by the driving current.

Feedback stabilization results are presented for an ion-sound instability. Sensing of the instability was achieved by a photodiode outside the plasma, and the suppressor element was an electron-cyclotron resonance structure remote from the plasma. Radiation from this structure heats the electrons locally and feedback is achieved by amplitude modulation of the electron-cyclotron resonance at the instability frequency. A theory is developed which predicts the variation of the instability amplitude and frequency in terms of the change in electron temperature $\Delta T$, fractional modulation $f$, and phase change in the loop, $\varphi$. Comparison between theory and experiment shows good agreement.

Turbulent diffusion coefficients for an assumed spectrum are derived using fluid equations, a crucial assumption being that the ion motion parallel to the magnetic field is hindered by the collision of ions with neutrals. The result shows that the turbulent diffusion coefficients depend on geometric factors, as well as on the level of fluctuations. This dependence on geometric factors may explain the experimentally observed difference in confinement times in different toroidal plasma confinement devices.

To test the idea that surface irregularities can pin fluxons, regular parallel microgrooves were created in the surfaces of homogeneous cast In-2% Bi foils by pressing diffraction gratings into the foils. The pinning force thus induced was zero for flux flow parallel to the grooves and a maximum for perpendicular flux flow; a very simple dependence on the spacing and strength of the pinners was found.

Thermal conductivity enhancements due to magnetic phase transitions have been observed for chromium, chromium-molybdenum alloys, and several rare-earth metals. The phenomenon can thus no longer be considered an uncommon one in metallic systems. In chromium, it appears to be sensitive to the microscopic state of particular samples.

The observed degeneracy of mutually exclusive infrared- and Raman-active modes in Mo${\mathrm{S}}_2$ is traced by means of group theory to the weak van der Waals interaction between layers.

Over 50% proton polarization has been attained in three sulfate alum crystals containing dilute ${\mathrm{Cr}}^{3+}$ ions, at 1 K and ∼19.5 kG, with limited microwave power (∼¼ W). The EPR spectra are dominated by the (-½, ½) transition, with linewidths varying from 10 to 22 G. Al(N${\mathrm{H}}_4$) alum should make useful polarized proton targets because it contains 1.97 times as much hydrogen by weight as lanthanum magnesium nitrate.

The pressure variation of resistivity and optical absorption in SmTe has been studied. A continuous pressure-induced semiconductor-to-metal transition is observed, which we ascribe to the promotion of electrons from the $4f$ level into the conduction band as the gap between them shrinks with pressure and finally vanishes. The gap deduced from the saturation resistivity ratio $\frac{\rho {\mathrm{}\left(P\right)\mathrm{}}_{\mathrm{sat}}}{\rho \mathrm{}\left(0\right)\mathrm{}}$ is in good agreement with the gap of 0.62 ± 0.02 eV obtained from infrared absorption data.

The second-order effects of intrinsic two-phonon processes in the electron-phonon interaction are shown to give rise to a contribution to the thermopower of metals of a magnitude and shape identical to that previously attributed solely to phonon drag.

We present a new method to investigate the exciton spectrum in the case of degenerate bands. Using symmetry considerations and second-order perturbation theory, we obtain a simple analytical expression for the binding energy as a function of the band parameters. Direct excitons in group IV elements, III-V compounds, and II-VI compounds can be investigated by this method. Results are given for Ge, GaAs, InSb, ZnSe, and CdTe.

We present a soluble model of electrons interacting with lattice vibrations which displays metallic, superconducting, and insulating phases. We solve the thermodynamics of this model and discuss its properties. The metal-insulator phase transition is second order for sc and bcc tight-binding bands. With sufficient deviation [(5-10)% for coupling constant $\tilde{g}=0.1\mathrm{}$] from such band structure the transition becomes first order. Above this, the "collective insulator" ceases to exist. Our model might apply to certain transition-series metal oxides, such as V${\mathrm{O}}_2$.

The temperature and electric field dependence of a 3500-${\mathrm{cm}}^{-1\mathrm{}}$ absorption band arising from hydrogen impurities in SrTi${\mathrm{O}}_3$ crystals have been measured. The phase transition at 102°K from a cubic to a tetragonal structure as well as externally applied electric fields at low temperature cause a multitude of symmetrically different positions for the impurity. The corresponding frequency shifts can be correlated with the structural changes in the crystal and with the behavior of the low-frequency phonons.

The reaction ${\mathrm{Zr}}^{96}({\mathrm{He}}^3,t){\mathrm{Nb}}^{96}$ was studied and six states belonging to the $\left(\pi g_{\frac{9}{2}}\right){\left(\nu d_{\frac{5}{2}}\right)}^{-1\mathrm{}}$ configuration were identified. The energies and spin assignments agree well with those derived by use of the Pandya transformation from the known states of ${\mathrm{Nb}}^{92}$ belonging to the $\left(\pi g_{\frac{9}{2}}\right)\left(\nu d_{\frac{5}{2}}\right)$ configuration.

It is shown that the nuclear shell effects on the level density disappear even at medium excitation energies of the order of 40 MeV. Fission-fragment anisotropy data for actinide nuclei having double-humped fission barriers are shown to contain evidence for this effect. The implication of this effect on the production of superheavy nuclei is pointed out.

We derive the relation ${\Gamma }_{\gamma }(\xi ,T,T_z)=a^{\prime }(\xi ,T)+b^{\prime }(\xi ,T)T_z+c^{\prime }(\xi ,T)T_z^{}{}_{}{}^2$ for the total radiative decay rates of isospin multiplet members.

We have measured the yield of $\varphi$ mesons photoproduced from carbon and decaying into muon pairs. We find that the product of the lepton-pair branching ratio for the $\varphi$ and the $t=0\mathrm{}$ photoproduction cross section is (0.66 ± 0.10) × ${10}^{-4\mathrm{}}$ mb/Ge${\mathrm{V}}^2$. This number is compared with existing measurements of the branching ratio and the cross section.

We present evidence for three boson structures with masses 1.65, 1.97, and $2.16 \frac{\mathrm{GeV}}{c^2}$ and widths less than $80 \frac{\mathrm{MeV}}{c^2}$ from a study of the reaction ${\pi }^{+}p\to p{\pi }^{+}{\pi }^0$ at $13.1 \frac{\mathrm{GeV}}{c}$. These structures are shown to have $I^G=1^{+}$, therefore excluding even $J$ assignments. This result favors the interpretation of the 1.97 state as a member of the $A_2$ daughter trajectory.