The method of ionic thermocurrents has been combined with optical-absorption and radiation-damage techniques to investigate the production of photochromic centers in Ca${\mathrm{F}}_2$:Ce. It is found that the initial growth of the photochromic bands under x irradiation is correlated with the destruction of the 243-nm band initially, and with an exponential decay of dipole centers at later stages. The maximum oscillator strength of the 243-nm band is calculated. It is also found that one photochromic center is formed for each four dipole centers destroyed, independent of dose rate.

TmAs${\mathrm{O}}_4$ undergoes a cooperative Jahn-Teller distortion at 6.0 K. At $T<\mathrm{}6\mathrm{}$ K there is a temperature-dependent critical field ${\overrightarrow{\mathrm{B}}}_c$ at which a cooperative distortion back to the high-temperature phase occurs. For $B<\mathrm{}{B}_c$, the distortion directions in the basal plane are the (110) and the ($1\overline{1}0$) directions and are magnetically controllable.

Photoemission energy distributions at high photon energies permit one-electron measurements of the electronic energy levels and level widths of chemisorbed gases on clean metal surfaces at fractional monolayer coverages. Chemisorbed CO on Ni exhibits energy levels at 7.5 and 10.7 eV below the Fermi level $E_{\mathrm{F}}$ while chemisorbed O on Ni shows a 2-eV width level at 5.5 eV below $E_{\mathrm{F}}$. Upon increased oxygen exposure, a surface oxide of Ni is formed which exhibits valence bands about 8.5 eV wide.

A latent heat, hysteresis, and superheating and supercooling have been observed in a Cr single crystal by means of an extension of the ac calorimetric method.

It has been observed that applying sufficiently large uniaxial stress to ${\mathrm{Cr}}_2$${\mathrm{O}}_3$ induces in its ${}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}E$ optical-exciton absorption spectrum changes that are nearly identical to those observed when magnetic-field—induced spin flop occurs. This is interpreted as evidence that uniaxial stress induces spin flop in ${\mathrm{Cr}}_2$${\mathrm{O}}_3$. A phenomenological discussion is given.

We report measurements of the dispersion of singlet-triplet magnetic excitons as a function of temperature in the singlet-ground-state ferromagnets fcc Pr and ${\mathrm{Pr}}_3$T1. Well-defined excitons are observed in both the ferromagnetic and paramagnetic regions, but with energies which are nearly temperature independent, in disagreement with existing theory.

The well-known plane-fronted waves with parallel rays, exact solutions of the vacuum Einstein gravitational field equations, are generalized to exact solutions of the equations of $f-g$ gravity theory proposed by Isham, Salam, and Strathdee in regions free from matter.

Inclusive ${\pi }^{+}$, ${\pi }^{-}$, and $K^0$ production from $11.8-\frac{\mathrm{GeV}}{c}$ $K^{+}p$ is isotropic in the center-of-mass system and obeys a Bose-Einstein distribution over a limited energy range. The values of the parameter $\mathrm{kT}$ are observed to be consistent with the pion mass.

Using a simplified multiperipheral model, we study the behavior of the longitudinal pion spectrum for the process $\mathrm{pp}\to \pi +$ anything in the region of small values of $x=\frac{2{p_{\parallel }}^{\mathrm{c}.\mathrm{m}.\mathrm{}}}{s^{\frac{1}{2}}}$. We expect the occurrence of an inverted cusp in the spectrum at very large energies and the appearance of noticeable effects at the energies of the CERN intersecting storage rings.

The Coulomb field is included in the analysis of scattering by deuterium via an exact solution within the framework of Glauber theory. New multiple-scattering effects occur. These involve double scatterings by the Coulomb interaction and the neutron and by the Coulomb interaction and the proton strong interaction, and triple scattering by the Coulomb interaction, the neutron, and the proton strong interaction. Coulomb effects in $\mathrm{pp}$ collisions are obtained as a special case of $\mathrm{pd}$ scattering.

Wyler's expression for $\alpha$ in terms of the Euclidean volumes of certain bounded spaces agrees with experiment only if the radius of these spaces is arbitrarily chosen to equal 1. However, the relationship between these spaces and the invariance group $O(n,2\mathrm{})\mathrm{}$ of the $n$-dimensional wave equation is independent of the radius. There is no known reason for setting the radius equal to one.

We study the dips and breaks in proton-proton and proton-antiproton elastic scattering data. We find that all the structure is well understood in terms of the global curves of Odorico, which are simply curves of $cos\varphi$=constant, where $cos\varphi$ is the proposed new variable. In particular, the low-energy $p\overline{p}$ data of Cline, English, and Reeder are reviewed and found to be well explained in terms of the Odorico curves.

Mean lives of He I are deduced from the Hanle curves for high-velocity atoms excited in a gaseous target. For long—mean-life levels we observed oscillations in agreement with a partial precession of the dipoles around the magnetic field. For the $3p{}_{}{}^1{}_{}{}^{}P$ level, the Hanle curve is not perturbed by self-absorption using this method, and the measured mean life (1.8±0.1 nsec) is in good agreement with the theoretical value.

Three spectral lines corresponding to Bohr orbit transitions $n=3\mathrm{}\to 2$, $n=4\mathrm{}\to 2$, and $n=5\mathrm{}\to 2$ in liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ have been measured with a resolution of 340 eV. Intensities per stopped kaon were 0.09, 0.05, and 0.02, respectively. No evidence was seen for transitions to $n=1\mathrm{}$ (intensity < 0.004).

From measured Compton profiles of C${\mathrm{H}}_4$, ${\mathrm{C}}_2$${\mathrm{H}}_4$, and ${\mathrm{C}}_2$${\mathrm{H}}_6$, experimental values are found for the Compton profiles of C-H, C-C, and C=C bonds. These profiles are then used successfully to predict within experimental accuracy the measured Compton profiles of ${\mathrm{C}}_3$${\mathrm{H}}_6$, ${\mathrm{C}}_6$${\mathrm{H}}_6$, ${\mathrm{C}}_6$${\mathrm{H}}_{12}$, ${\mathrm{C}}_6$${\mathrm{H}}_{14}$, and ${\mathrm{C}}_8$${\mathrm{H}}_{10}$. This success is strong evidence that the identified C-H, C-C, and C=C bonds are indeed localized and transferrable.

A many-atom representation has been derived in which bound atoms or molecules are described by elementary Bose or Fermi operators, the field operators for nuclei and electrons referring only to unbound particles. The Hamiltonian thus obtained contains not only nucleus-nucleus, electron-electron, and nucleus-electron Coulomb interactions, but also atom-atom, atom-nucleus, and atom-electron Coulomb and exchange interactions, including breakup and recombination terms.

The Kubo formula is used to evaluate the bulk electrical conductivity of a two-dimensional guiding-center plasma in a strong dc magnetic field. The particles interact only electrostatically. An "anomalous" electrical conductivity is derived for this system, which parallels a recent result of Taylor and McNamara for the coefficient of spatial diffusion.

We report the first measurements of the specific heat of a metastable, superheated, pure liquid (${\mathrm{He}}^3$). The specific heat shows no evidence of any singularity near the onset of metastability. We have also observed the lifetimes of metastable states as the ${\mathrm{He}}^3$ is cooled at constant density. For densities near the critical density, lifetimes decrease abruptly in an extremely narrow, reproducible temperature interval. This may indicate the onset of an "intrinsic" instability.

The cross-field anomalous resistivity due to the electron-cyclotron drift instability is shown to persist in the nonlinear regime as a result of mechanisms which depend critically on the magnitude of the magnetic field.

Reversal of the axial magnetic field in a magnetic-mirror trap is achieved by injection of a 30-kA, 0.34-MeV beam of electrons.