The impact-parameter calculations of Hansteen et al. [J. Phys. B 17, 3545 (1984)] for K-shell ionization are used to predict the cross sections for the double ionization of ${\mathrm{H}}_2$ and He by ${\mathrm{H}}^{+}$ and ${\mathrm{D}}^{+}$ projectiles as a function of projectile velocity. The calculated values in the case of the ${\mathrm{H}}_2$ target are typically a factor of 12 lower than the measured values, but the calculations and measurements show similar velocity dependencies. The results indicate that for projectile energies less than 1 MeV/amu, the double-ionization process of ${\mathrm{H}}_2$ occurs mainly by two independent interactions between the electrons and projectile. For the He target, the calculated and measured values for the double-ionization cross section are much closer in magnitude, but the calculations predict a more rapid falloff with projectile velocity than is observed.

Magnetic monopole detectors based on the premise that these particles can create the triplet metastable state in helium, He($2^3$S), exclusively and without ionization are believed to be feasible. In one of these, He($2^3$S) is detected in an ionization chamber array using both pure helium and a mixture of He+${\mathrm{N}}_2$ in which Penning ionization occurs. In the second version, resonance ionization spectroscopy is used to selectively ionize He($2^3$S). In both cases, monopoles with velocities greater than ${10}^{\mathrm{-}4}$c can be searched for with both large and reliable detectors.

The relative photoabsorption cross section of barium in the spectral range from the ionization limit at 237.9 to 120 nm has been measured and the results of previous measurements extending to 170 nm confirmed. The cross section is found to rise slowly at wavelengths shorter than 130 nm and to decrease in the region between 140 and 130 nm.

The power and scope of configuration-interaction studies can be greatly extended by limiting the variational calculation to a finite volume of configuration space. The energy levels and wave functions of an electron which escapes from that volume are then accurately described by quantum-defect theory. Adaptation of standard multiconfiguration Hartree-Fock procedures to the variational calculation of R matrices is accomplished easily, giving a simple, fast, and efficient tool for investigating channel-coupling mechanisms over broad ranges of energy.

Photoelectron angular distributions for the 6s, 7s, and 8s subshells of cesium are calculated in the Dirac-Fock approximation. Variations in the angular-distribution-asymmetry parameter β are concentrated toward lower photoelectron energies as one moves along the Rydberg series.

Wavelengths for the 2$s^2$2$p^5$3s-2$s^2$2$p^6$3p transitions in the neonlike isoelectronic sequence have been calculated by means of the relativistic code of Grant et al. [Comput. Phys. Commun. 21, 207 (1980)]. Mixing with the 2s2$p^6$3l configurations is found to be important. A separate optimization for the 2$p^5$3p ${}^1$$S_0$ state is needed. Comparisons with observations in Ti xiii, Fe xvii, Se xxv, and Y xxx show excellent agreement.

In a previous publication [Phys. Rev. A 31, 1440 (1985)], we determined the linewidth enhancement factor (LEF) of the microwave-power-broadened linewidth of the 0-0 hyperfine transition in optically pumped alkali-metal vapors. This factor is essentially a measure of the ratio of the transition linewidth to the microwave Rabi frequency. In the previous study, optical pumping out of only one hyperfine multiplet was considered. In the present study, the expressions are generalized to include optical pumping out of both hyperfine multiplets simultaneously. Dramatic changes in the behavior of the LEF as a function of the optical-pumping rate are predicted.

The electron affinity of atomic oxygen, an important calibration standard in negative-ion photoelectron spectroscopy, has been determined by tunable-laser photodetachment in a coaxial laser–ion-beam spectrometer to be 11 784.645±0.006 ${\mathrm{cm}}^{\mathrm{-}1}$. In addition, the spin-orbit splitting between the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{1/2}^{}{}_{}{}^{}$ states of ${\mathrm{O}}^{\mathrm{-}}$ was found to be 177.13±0.05 ${\mathrm{cm}}^{\mathrm{-}1}$.

We have measured the phase diagram for mixtures of chiral and racemic cholesteric S-(+)-4-(2-methylbutyl)phenyl-4-decyloxyben- zoate (CE6) in order to study the effect of changing chirality on the appearance of the cholesteric blue phases. We have also measured the latent heats at the isotropic transitions. Our phase diagram is compared with the Landau theory of Hornreich and Shtrikman and the data of Marcus and Goodby.

We calculate the interaction and excess free energies of the electron system at finite temperatures on the basis of the Singwi-Tosi-Land-Sjölander approximation [Phys. Rev. 176, 589 (1968)]. The results are parametrized in the form of analytic formulas, which adequately describe the equation of state for homogeneous, paramagnetic electron liquids over a wide range of the density and temperature parameters.

We calculated quantum mechanically the response of surface-state electrons to an applied microwave field. By solving an effective Schrödinger equation which takes into account both bound-bound and bound-continuum transitions to all orders, we show that the ionization proceeds via direct coupling to the continuum. This contrasts with the classical description, where ionization occurs as the result of a diffusive energy gain.

When heated from below, layers of binary solutions with negative Soret coefficients present heating curves with characteristic shapes: A negative slope exists in the vicinity of the convection onset and a hysteresis appears. In the literature the values of the Soret coefficients for diluted solutions of methanol in benzene are generally reported as negative. In very carefully executed Bénard experiments with this system, we do not observe heating curves with such negative slopes. Our measurements, using convection in order to quantify the concentration gradients, are not in agreement with the reported Soret coefficient values.

It is shown that line-shift calculations for neutral hydrogen to second order in the atom-electron interaction are very dependent on the strong-collision cutoff procedure.

I respond to the Comment by Iglesias, Boercker, and Lee (preceding paper).

Bare Cl nuclei were decelerated and then allowed to capture a single electron in a He-gas target. By this method pure hydrogenlike Cl ions were prepared in an excited state from which the 2p-1s transition wavelength could be accurately (≊${10}^{\mathrm{-}5}$) measured without distortion by spectator electrons. After Doppler correction by utilizing measurements at four different ion velocities (v/c≊0.038–0.067), fine-structure splitting and 1s Lamb-shift values were determined within 15% error bars, which, while far from the potential possible limits of our method, are in agreement with theoretical results.

The absolute cross section for the energy transfer between the nP Rydberg atom (n=35–60) and the ground-state (5S) atom of rubidium is measured to be 4.8×${10}^2$ A${̊}^2$ for thermal collisions at 420 K. This value of the cross section is in agreement with the calculated value for resonant charge transfer at the relevant collision energy. It is concluded that the energy transfer process is essentially charge transfer between the Rydberg ion core and the ground-state atom, where the Rydberg electron stays as a spectator.

Absolute cross sections for ${\mathrm{Li}}^{\mathrm{-}}$ photodetachment have been measured near the Li($2^2$P)+εs channel threshold. The energy dependence deviates rapidly from normal Wigner-cusp behavior on each side of threshold. From an analysis of the total cross sections in terms of a two-channel scattering theory that includes the effects of a virtual state, a parametric expression has been derived which accurately describes the energy dependence. A least-squares fit of the data yields the position of the virtual state (55±10 meV below $2^2$P), the phase shift at the Li($2^2$P)+εs threshold (1.4±0.1 rad), and the electron affinity of Li (617.3±0.7 meV).