Electroreflectance spectra were measured at room temperature to determine the energies of the lowest gap, $E_0$, and its spin-orbit-splitting gap, $E_0+{\Delta }_0$, in $\mathrm{Zn}{\mathrm{Se}}_x{\mathrm{Te}}_{1-x}$ alloys as a function of composition $x$. The variation with $x$ of the spin-orbit splitting at the $\gamma$ point, ${\Delta }_0$, was found to show convex behavior, confirming our preliminary results deduced from reflectivity measurements. The deviation from linearity of ${\Delta }_0$ is 0.146 eV at $X=0.5\mathrm{}$. The bowing parameters of the $E_0$ and $E_0+{\Delta }_0$ gaps were determined to be 1.266 ± 0.023 and 0.681 ± 0.040 eV, respectively.

By applying yield spectroscopy we could confirm recent absorption measurements locating the onset of ${\mathrm{Li}}^{+}$ ${\mathrm{Li}}^{+} 1s$ transitions at 54 eV. From energy-distribution-curve measurements using 120-eV photons, the ${\mathrm{Li}}^{+}$ ${\mathrm{Li}}^{+} 1s$ separation from the top of the valence band is found to be 50.2 eV. Combining these numbers with the band gap (13.6 eV), we find an electron-hole interaction energy of 10 eV. This is discussed in the context of two the-oretical calculations of ${\epsilon }_2$ spectra.

Nonlinear and linear optical responses of mobile holes in the "camelback"-shaped valence band of tellurium are calculated without expansion in powers of electric field of the wave. We predict unusual nonlinear properties depending on intensity, frequency, and polarization of the driving field, as well as on the free-hole concentration and hydrostatic pressure.

We have considered the six interaction potentials involved in distorted-wave Born-approximation (DWBA) calculations and find that the inclusion of Coulomb interaction potentials which are usually neglected improve heavy-ion predictions in two ways: (1) The difference between cross sections calculated in the post and prior representations is reduced to a few per cent, and (2) the energy dependence found in spectroscopic factors derived from standard DWBA calculations is removed.

Lifetime and $g$-factor measurements on the $I=J+2\mathrm{}$ state in the decoupled bands of ${}_{}{}^{157}{}_{}{}^{}\mathrm{Er}$ and ${}_{}{}^{159}{}_{}{}^{}\mathrm{Er}$ are shown to be in agreement with those expected from the rotation-aligned coupling scheme. Such measurements provide a general way to differentiate this coupling scheme from the better-known weak- and strong-coupling schemes.

The model of a single-$j$ nucleon coupled to an asymmetric rotor is applied to new experimental results on yrast bands in ${}_{}{}^{187}{}_{}{}^{}\mathrm{Ir}$, ${}_{}{}^{195}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Tl}$. The core asymmetry is shown to account for systematic trends in the high-spin spectra. Information on the shape dependence of moments of inertia is obtained which supports the idea of nuclear flow of irrotational type.

We have observed 1522 neutrino events with a ${\mu }^{-}$ secondary and 8 events with a ${\mu }^{+}$ secondary from a beam consisting mostly of neutrinos. The ${\mu }^{+}$ events are consistent in number and kinematic properties with beam contamination by ${\overline{\nu }}_{\mu }$. This experiment sees no evidence for production of heavy positively charged leptons. Assuming a coupling constant equal to the universal Fermi constant and a branching ratio to muons $B=0.3\mathrm{}$, our 90% confidence lower limit corresponds to $M_{Y^{+}}\gtrsim 8.4$ ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.

Data from $p+p\to p+X$ at 102, 205, and 405 GeV and from ${\pi }^{-}+p\to p+X$ at 205 GeV exhibit an approximate scaling property in the charged-prong multiplicity distributions as a function of the missing mass for the range $5<~M_X<~13$ GeV.

The effect of finite nuclear size on the vacuum-polarization charge density is studied. The results to third order $\alpha {\left(Z\alpha \right)}^3$, and to all orders $\alpha {\left(Z\alpha \right)}^n$, $n>~3$, are presented with special attention focused on the $5g_{\frac{9}{2}}-4f_{\frac{7}{2}}$ transition in muonic Pb. In addition, the accuracy of analytic calculations exploiting the smallness of the electron mass and of the nuclear radius is discussed.

In order to complete the identification of molecular-orbital $K$ x-ray spectra, we have worked out the expected spectral yields and compared them with experimental spectra produced by 30- and 60-MeV Br and 82- MeV I beams. Independently, we have determined the dominant mechanism of molecular-orbital $K$ x-ray production in 30-MeV Br + Br collisions by diluting the Br density in a solid target.

We have measured the spectral line profiles of the optical satellites emanating from the $(2^{3}S,2^{3}P)-(4^{3}S,4^{3}P)$ excited state manifolds of a low-pressure helium plasma. These satellites are induced by the presence of a C${\mathrm{O}}_2$ laser field. Detailed spectra are presented for the $2^{3}P-4^{3}S$, 4713-Å HeI allowed line and its associated near satellite. A theoretical model, valid for large, near-resonant interactions is described. This theory is seen to be in good agreement with the experimental results.

A molecular-beam apparatus is used in conjunction with a tunable laser to determine absolute cross sections for the photoionization of helium $3{}_{}{}^1{}_{}{}^{}P$, $4{}_{}{}^1{}_{}{}^{}P$, $5{}_{}{}^1{}_{}{}^{}P$, $3{}_{}{}^3{}_{}{}^{}P$, $4{}_{}{}^3{}_{}{}^{}P$, and $5{}_{}{}^3{}_{}{}^{}P$ atoms excited optically from the $2{}_{}{}^{1,3}{}_{}{}^{}S$ metastable levels. The photoionization cross section for each of these states is determined at the wavelength used for its excitation from the metastable state. The results are compared with those of recent unpublished calculations.

Recursion relations correct to lowest order in $\epsilon =4-d$ are obtained for simple models representing the critical dynamics of a binary liquid, a Heisenberg antiferromagnet, superfluid helium, and related systems. The exponents for the divergences of the transport coefficients satisfy the "scaling" relations predicted by mode-mode coupling theory. The viscosity of the binary liquid is predicted to diverge as $k^{-\frac{\epsilon }{19}}$ near $d=4\mathrm{}$, which is a new result.

Critical flow velocities measured by Doppler-shifted third sound in unsaturated helium II films are shown to exhibit a well-defined maximum as a function of film thickness and at this maximum to be considerably higher than those usually found in film flow. In addition the critical velocity is strongly temperature dependent below the maximum and relatively temperature independent above.

Using a standard acoustical technique, we present new data concerning the attenuation of 9.4-GHz phonons in thin helium films. The mechanical resonance of the film is observed in the temperature range 1.4 to 2.1 K. A comparison with the bulk case is made.

The slowing down of ions by a degenerate electron plasma is calculated by means of the random-phase approximation. It is shown that high compressions greatly reduce the ability of electrons to slow down ions. These results indicate that nuclear burning of a DT plasma can proceed as a chain reaction, even at low temperature, at densities about ${10}^5$ times the solid density.

Infrared studies of thin films of TTF-TCNQ are analyzed to obtain the frequency-dependent conductivity. In the metallic state the results indicate an energy gap (0.14 eV) with a collective mode at zero frequency. Below 58 K the conductivity peak moves away from zero frequency into the far infrared.

The high-frequency exponential wing of the reststrahlen band of NaF is decomposed into a number of $N-\mathrm{phonon}$ absorption spectra ($N=2,3,4,5\mathrm{}$) by means of a temperature analysis. Overall agreement of the individual spectra with recent theoretical predictions is good, except for a fairly pronounced structure which indicates particularly strong contributions from certain frequencies of the TO and LO phonon branches.

The distribution function governing the equilibrium separation of two atoms on a single crystal plane has been measured for the first time. Quantitative determinations for tungsten atoms self-adsorbed on the (211) and (321) planes of tungsten reveal that, for interatomic distances $R>\mathrm{}7\mathrm{}$ Å, the behavior of the atoms conforms to that of independent particles. Long-range interactions are below the detection limit of $\approx \frac{\mathrm{kT}}{2}$, where $T$ is the equilibration temperature, in agreement with present theories of interatomic interactions.

Experimental field-emission spectra for the principal planes of the fcc transition-group metals (iridium, rhodium, palladium, and platinum) exhibit significant systematic agreement with relativistic augmented-plane-wave band calculations by Andersen. Surface band-edge contraction as well as effects of chemisorbed hydrogen and nitrogen are discussed.