We have recorded high-resolution resonant Raman spectra of molecular iodine which show very pronounced systematic spectral band-shape variations with incident laser frequency. This frequency dependence and the presence of the multiple overtones in resonant Raman scattering from iodine may be explained by a theory in which the scattering intensity depends on Franck-Condon overlap integrals. We have obtained semi-quantitative agreement between the observed spectra and spectra calculated from this theory.

Measurements of the energy distribution in the presence of adsorbed CO are given for the (110), (210), and (100) planes of W. The results are discussed in terms of binding models.

An intense pulsed electron beam ($\frac{\nu }{\gamma }\sim 2$) was used to heat electrons in a target plasma in a magnetic field. A strong beam-plasma interaction was observed. Measured heating levels were found to be consistent with a two-stream instability calculation and return-current heating estimates. Energetic counter-streaming electrons were detected in the plasma during the beam pulse and possible sources of these electrons are suggested.

The relative viscosity $\eta$ of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured along the melting curve from 10 mK to about 1 mK with a vibrating-string viscometer. As the temperature is reduced, $\eta$ first increases as expected until the pressure anomaly "$A$" is reached. The viscosity then starts to decrease, has a discontinuous drop at the pressure anomaly "$B$," and then continues to diminish rapidly. The lowest measured value of $\eta$ is 1000 times smaller than that at point $A$. This must be regarded as strong evidence for superfluidity.

The relaxation time ${\tau }_R$ for the density of superconducting electrons to achieve equilibrium with a change in current density has been measured near $T_c$, using a large, chopped dc and a small continuous rf current. The changeover from $\omega {\tau }_R\ll 1$ to $\omega {\tau }_R\gg 1$ has been observed in the frequency range $30 \mathrm{MHz}<~f<~900 \mathrm{MHz}$. In the temperature range $0.95<~\frac{T}{T_c}<~0.995$, the relaxation time was found to be ${\tau }_R=2.6\mathrm{}\times {10}^{-10\mathrm{}}{(1-\frac{T}{T_c})}^{-\frac{1}{2}}$ sec.

Acoustic damping and dispersion in EuO have been measured at low kilohertz frequencies near the ferromagnetic critical point. The experimental observations are discussed in terms of thermoelastic and critical dissipative processes. Bounds are established for the critical relaxation rate for sound, $2\times {10}^5<{{\tau }_c}^{-1\mathrm{}}<2\mathrm{}\times {10}^7$ ${\sec }^{-1\mathrm{}}$, in order-of-magnitude agreement with the EuO spin-lattice relaxation rate calculated by Huber.

We have investigated the problem of plasmon observation using high-energy photons within the context of the random phase approximation. It is shown that the experimental results from a study of Be by Miliotis can be readily understood from this point of view. It is further shown that these results include both collective and single-particle effects and that the collective effects persist well beyond the "critical wave vector." We discuss the concept of a critical wave vector.

I have evaluated exactly the random-phase-approximation surface-plasmon linear dispersion coefficient, $\alpha ={\alpha }_1+i{\alpha }_2\equiv limit\; of{q}^{-1\mathrm{}}[\frac{{\omega }_s\mathrm{}\left(q\right)\mathrm{}}{{\omega }_s\mathrm{}\left(0\right)-1\mathrm{}}\text{as}q\to 0]$ for $2<~r_s<~6$, using self-consistent (Lang-Kohn) potential barriers, and also using model barriers of adjustable surface diffuseness, $a$. I find $\alpha$ to be markedly sensitive to $a$, casting doubt on the reliability of using non-self-consistent model barriers to determine surface-plasmon properties. At Al density ($r_s\simeq 2$), for example, I find $\alpha =-(0.24+0.57i)\mathrm{}$ Å using the Lang-Kohn potential, in contrast to Beck and Celli's step-function ($a=0\mathrm{}$) barrier result, $\alpha =-(0.07+0.2i)\mathrm{}$ Å.

The imaginary part of the dielectric function, the energy band structure, and the reflectivity of the ternary compound ZnGe${\mathrm{P}}_2$ are calculated using the empirical pseudopotential method. A critical point analysis in the Brillouin zone is discussed in detail to explain prominent optical structure. Spin-orbit corrections to the band structure were calculated at a few points in the Brillouin zone.

We have observed electroreflectance structure in ZnGe${\mathrm{P}}_2$ at the pseudodirect energy gap, the direct energy gap derived from the indirect gap in GaP. The direct energy gap is also observed at higher energy. We also observe the direct energy gap of ZnSi${\mathrm{P}}_2$ some 1.0 eV above the absorption edge previously reported. The polarization selection rules observed at the direct gap in ZnSi${\mathrm{P}}_2$ are opposite to those found in all other II-IV-${\mathrm{V}}_2$ compounds investigated, and raise a fundamental question as to the physical origin of the crystal field splitting of the valence bands in these compounds.

Measurements of the cross section, the vector analyzing power, and the three tensor analyzing powers have been made for deuteron elastic scattering from ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ at 5.5 MeV. The measurements are explained by an optical-model potential whose spin-dependent parts are calculated from the nucleon-nucleus potential. The predicted spin-orbit potential, which is considerably different from the potentials used in previous phenomenological analyses, also gives excellent agreement with the vector analyzing power at 9 MeV.

The theory of Lane for the anomaly in the excitation function of the ($d,p_0$) reaction near the threshold of the analog ($d,n$) channel has been applied to polarized-beam measurements. The anomaly effects, observed at several angles in both cross section and analyzing power in the reaction ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}(d,p_0){}_{}{}^{89}{}_{}{}^{}\mathrm{Sr}$, are reproduced by a distorted-wave Born-approximation calculation, if the radial matrix elements for the proton exit channel with $l=1\mathrm{}$, $j=\frac{3}{2}$ are modified by a resonance term.

Cross sections for ($p,n$) transitions to analog states for targets of Ta, Au, and Bi have been measured. The cross section and decay width observed for Bi are inconsistent with those obtained from ($p,np$) measurements. We propose an explanation for these discrepancies.

We report the results of a comprehensive computer simulation of angular distributions of 4.0-MeV protons scattered by a 3-μm-thick Ge crystal and emerging near a $〈110〉$ direction. They show that interpretation of measured blocking distributions to obtain short nuclear lifetimes is strongly dependent on the recoil direction and depth distribution of the recoiling compound nuclei in the crystal. This dependence is explained in terms of the associated flux peaking effect in particle channeling.

A $t$-matrix calculation of the ground-state energy of cold neutron matter has been performed and it is shown that neutron matter solidifies at a density of the order of 1.6 × ${10}^{15}$ g/${\mathrm{cm}}^3$, thus implying the existence of a solid core inside heavy neutron stars.

It is shown that the fourth-order vacuum polarization correction to the annihilation diagram contributes $\Delta \nu =-\frac{1}{4}{\alpha }^4{R}_{\infty }\ln {\alpha }^{-1\mathrm{}}$ to the positronium ground-state hyperfine structure. This leads to a reduction of 11.3 MHz in the previous theoretical prediction which greatly improves the agreement between theory and experiment.

A crystal spectrometer is used to study foil-excited fluorine beam x rays. The transitions from $2{}_{}{}^1{}_{}{}^{}P$ and $2{}_{}{}^3{}_{}{}^{}P$ to $1{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ He-like fluorine states and the transitions from ${}_{}{}^2{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}\mathrm{}\left(1\right)\mathrm{}$ and ${}_{}{}^4{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}\mathrm{}\left(1\right)\mathrm{}$ to $1{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ Li-like fluorine states are observed. Lifetimes of 0.537 ± 0.02 and 2.000 ± 0.025 nsec are measured and identified with the $2{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ and either the $2{}_{}{}^4{}_{}{}^{}{P}_{\frac{3}{2}}_{}^{\circ }{}_{}{}^{}\mathrm{}\left(1\right)\mathrm{}$ or $2{}_{}{}^4{}_{}{}^{}{P}_{\frac{1}{2}}_{}^{\circ }{}_{}{}^{}\mathrm{}\left(1\right)\mathrm{}$ decays, respectively.

A theoretical model is proposed which gives a qualitative explanation of the dominant features of the recent experiments of Monod, Hurdequint, Janossy, Obert, and Chaumount. In particular, the origin of the large enhancement factors is explained, and the spectrum observed in the implanted alloys is related to the spectra observed in the pure metal, and in a homogeneous magnetic alloy similar to the implanted layer.

We have shown by measuring the field-induced refractive index that molecular ordering in the isotropic phase of $p$-methoxy benzylidene $p-n$-butylaniline (MBBA) can be induced by an intense laser field. We have also measured directly the ordering relaxation time as a function of temperature. The results are compared with the predictions of the Landau—de Gennes model.

Resonance effects between orthogonal components of dynamic and quasistatic electric fields within a turbulent hydrogen plasma are shown to produce satellites on the ${\mathrm{H}}_{\beta }$ profile. The splitting on ${\mathrm{H}}_{\alpha }$, ${\mathrm{H}}_{\beta }$, ${\mathrm{H}}_{\gamma }$, and ${\mathrm{H}}_{\delta }$ profiles indicates that the quasistatic field strength is 0.9 × ${10}^7$ V/m. By using a helium tracer, comparison of a forbidden transition with its satellites indicates that the dynamic field (at the plasma frequency) is 1.3 × ${10}^7$ V/m.