The formalism needed for the computation of electric microfield distributions in plasmas is extended as follows: (i) The perturbing ions and electrons in the plasma are allowed to have different kinetic temperatures; (ii) two species of perturbing ions, of charge $Z_1$ and $Z_2$, may be present in any given proportion. Computed results are presented graphically for parameter ranges which are of interest in the study of laser-produced plasmas.

Kaonic-atom x-ray intensities of elements $Z=3, 6, 8, 11, \mathrm{and} 20$ were significantly reduced when the elements were in hydride form. The ratios $\frac{I\left(Z{\mathrm{H}}_m\right)}{I\left(Z\right)\mathrm{}}$ have a noticeable $Z$ dependence. Deuterides of C and O showed slightly less x-ray emission than their hydride counterparts.

The elastic scattering of electrons from molecular hydrogen is calculated by using the Glauber approximation (including the exchange effect) within the framework of independent scattering centers. Our theoretical values for differential cross sections give reasonable agreement with experimental data at incident energies of 30, 50, 100, and 200 eV.

The secondary-electron energy spectrum from ${\mathrm{He}}^{++}$/He has been measured with sufficient resolution to observe interference effects predicted by a Faddeev treatment of charge transfer. No oscillations were seen in the experimental results.

We offer a derivation of the mean-square deviation formula, recently employed in variational calculations of autoionizing states, from a time-dependent point of view.

The exact pulse solution of Brewer and Hahn for optical two-photon transitions is shown to reduce in the adiabatic limit to the two-photon vector model used by Grischkowsky, Loy, and Liao. The connection between the two approaches is explained and the complementary relationship between the two papers is discussed.

By means of a curved-crystal spectrometer an upper limit has been established for the intensity of the $K{\alpha }_1$ hypersatellite x-ray line emitted in the decay of ${}_{}{}^{169}{}_{}{}^{}\mathrm{Yb}$. From this limit the probability $P_{\mathrm{KK}}\left(\mathrm{IC}\right)$ of double $K$-shell vacancy creation per $K$ internal conversion can be deduced: $P_{\mathrm{KK}}\left(\mathrm{IC}\right)\lesssim 11\times {10}^{-5\mathrm{}}$.

Starting from a classical covariant equation of motion for the spin of a particle moving in a homogeneous electromagnetic field (the Bargmann-Michel-Telegdi equation), we show that the "relativistic mass" correction to the electron spin magnetic moment, which has been obtained previously from relativistic quantum-mechanical treatments of the Zeeman effect, may be reinterpreted as the combination of three classical effects: (i) the difference in time scales in the electron rest frame vis-a-vis the lab frame, (ii) the Lorentz transformation of the magnetic field between the two frames, and (iii) the Thomas precession of the electron spin due to the acceleration of the electron produced by the magnetic field.

Kinetic equations for classical time-dependent correlation functions of arbitrary phase-space variables are discussed. An operator identity is obtained that relates two previously derived forms of the memory operator. The Zwanzig-Mori projection-operator formalism expresses the memory operator in terms of projected dynamics, while the Mazenko form contains only unprojected, or Hamiltonian dynamics. With the single-particle correlation function as an example, the formal kinetic theory of Mazenko is simply derived and its relationship to the results of Gross and Boley exhibited.

A total of 18 ${}_{}{}^1{}_{}{}^{}S$ and ${}_{}{}^3{}_{}{}^{}S$ autoionizing states of He below the $n=2, 3, \mathrm{and} 4$ ionization thresholds are calculated using the time stability theory of autoionization.

The meaning of the word "symmetry" is discussed within the context of the noncrossing rule, and some arguments concerning the rule, recently given by Hatton, are criticized.

A reinterpretation of published trapped-electron data for the electron impact excitation of the $\mathrm{He}\left(2\mathrm{}{p}^2{}_{}{}^3{}_{}{}^{}P\right)$ state has been made using the predicted threshold law $\sigma \left(\epsilon \right)=C{\epsilon }^{\frac{3}{2}}$ for this parity-unfavored transition, $\epsilon$ being the energy difference between that of the incident electron and that of the final target state relative to the initial one. Correct analysis leads to a cross section 20% larger than previously reported.

Photoionization cross sections for all subshells occupied in the ground states of neutral oxygen and each positive ion ${\mathrm{O}}^{+n}$ ($n=1-6\mathrm{}$) have been calculated using Hartree-Slater wave functions. The results show that removal of a $2p$ or $2s$ electron has no effect on the $1s$ cross section other than shifting the threshold. The systematics of the cross section as a function of stage of ionization are analyzed, and the limits of applicability of the hydrogenic model are discussed.

Stark widths and shifts have been measured for six uv lines and three visible lines of neutral phosphorus in a wall-stabilized arc. The phosphorus is introduced into the arc in three forms: P${\mathrm{Cl}}_3$ vapor, atomized ${\mathrm{H}}_2$P${\mathrm{O}}_3$, and P${\mathrm{F}}_5$ gas. The results agree well with theory for both widths and shifts of the uv lines. It is suggested that the discrepancy with theory for the widths of the visible lines may be due to the neglect of Debye shielding in the theory.

We reexamine the forms of the angular distributions for photons which undergo Raman or Rayleigh scattering by unoriented targets. We show that a more complicated interference structure exists in the angular distribution if the molecular sample is optically active. This structure corresponds to the scattering of a mixture of linearly and elliptically polarized light, in contrast to ordinary molecules, which scatter a mixture of linearly polarized and unpolarized light. We discuss the possibility of the determination of the ellipticity of the scattered light by careful measurement of the angular distribution over a range of wavelengths.

The spin dependence of Rayleigh scattering has been measured by scattering 129-keV $\gamma$ rays of ${}_{}{}^{191}{}_{}{}^{}\mathrm{Os}$ on a magnetized iron-cobalt alloy. The circularly polarized $\gamma$ radiation was produced by nuclear polarization of ${}_{}{}^{191}{}_{}{}^{}\mathrm{Os}$ alloyed in iron at temperatures of 20-30 mK. For a mean scattering angle of 32° a spin dependence of $\Delta \sigma =(-0.216\mathrm{}\pm 0.033)\%$ has been found, which has the same sign as spin-dependent Compton scattering, the larger cross section appearing for the case where the photon and electron spins are antiparallel.

Resonant scattering of intense light is analyzed in the limit in which the separation of the spectral lines is large compared to their widths. The effect on the line intensities and widths of elastic and inelastic collisions in the impact approximation and of radiative damping is found. The limit of well-separated spectral lines allows simple solutions in a wide class of cases not easily treated outside this limit, in particular the case in which the upper laser-coupled state decays through a complicated cascade sequence to the lower laser-coupled ground state, or suffers collisional reorientation (depolarization) during the emission process.

This paper reports on our studies of near-resonant scattering of laser light in a collisional environment. A pulsed dye laser with a peak power of 55 MW/${\mathrm{cm}}^2$ was tuned near the 460.73-nm resonance line of strontium and the side emission was observed from an oven containing both strontium vapor and argon buffer gas. The emission was composed of three spectral components: Rayleigh scattering at the frequency of the laser ${\omega }_L$, fluorescence at the resonance frequency ${\omega }_0$ of strontium, and a third component at $2{\omega }_L-{\omega }_0$. These three components have been studied as a function of the frequency and intensity of the laser and also as a function of the argon buffer gas pressure. While the Rayleigh emission was found to vary as ${\Delta }^{-2\mathrm{}}$ ($\Delta ={\omega }_0-{\omega }_L$), the fluorescence component, which was produced by Sr-Ar collisions, was found to be asymmetric with the sign of $\Delta$ as predicted by line-broadening theory. By measuring the ratio of the intensities of the fluorescence and Rayleigh components, we were able to measure directly the collisional redistribution function, important in the study of radiative transfer in stellar and planetary atmospheres. At high laser intensities all three components were found to saturate. The results were compared with the theoretical predictions of Mollow's steady-state theory. Theoretical fits for the high-intensity results were obtained when the collisional cross sections were taken to be considerably smaller than in our low-intensity measurements. We believe the discrepancy lies in the use of a steady-state theory for a transient experiment. Effects of radiative trapping and spatial averaging are also discussed.

Oscillator strengths for the outer shells of the beryllium isoelectronic sequence are obtained using the relativistic random phase approximation in which the relativistic effects are included nonperturbatively. The results agree well with other accurate calculations that have been carried out for low-$Z$ elements. For high-$Z$ elements, our results should be very reliable. Both length and velocity formulas are used to calculate the oscillator strengths. The velocity formula is very sensitive to the weak inner-shell coupling, whereas the length formula is not. Inner-shell excitation energies and oscillator strengths are examined and compared with the helium isoelectronic sequence to show the effect of outer-shell screening.