Radiative-electron-capture (REC) cross sections for 40-80 MeV Cl ions incident on thin C foils are reported and compared with previous results using Cu targets. We find that the measured REC cross section per $K$ vacancy scales according to the number of "free" electrons on the target atom, i.e., those bound target electrons with a velocity much less than the incident projectile velocity. Comparison is made with the free-electron theory of Bethe and Salpeter and good agreement is obtained. Experimental and theoretical results are compared with those of Lindskog et al., and consideration is given to different ways of computing the theoretical REC cross section.

A model for sound propagation in critical binary mixtures is studied using renormalization-group and $\epsilon$-expansion methods. New scaling relations for the critical attenuation and dispersion are obtained and the corresponding scaling functions are calculated to $O\left(\epsilon \right)$. Our results are in good agreement with experiment.

$K$-shell ionization cross sections by low-energy proton impact have been calculated in the relativistic plane-wave Born approximation, taking into account the effects of binding-energy increase and Coulomb deflection. The calculated values are compared with the recent experimental cross sections of Zander and Andrews. It is found that the use of Dirac wave functions for target electrons improves agreement with the experimental results, but the theoretical predictions are still systematically higher at the lower proton energies.

We consider the effect of finite bandwidth of a strong pump field on the stimulated Raman scattering and the stimulated fluorescence due to a weak probe beam. When a decorrelation approximation is valid, it is possible to express the resulting scattering in terms of simple convolution integrals with the strong-field intensity spectrum.

Yu et al. [Phys. Rev. A 18, 1591 (1978)] have obtained the conditions for high-power laser solitons in plasmas. Conditions are restated in a more directly verifiable way and proved more rigorously.

The probability of double-$K$-vacancy production accompanying internal conversion in three different atoms. In ($Z=49\mathrm{}$), Ba ($Z=56\mathrm{}$), and T1 ($Z=81\mathrm{}$) has been measured in coincidence experiments. The comparison of our experimental results with various theoretical approaches exhibits the importance of correlation effects between the two $K$ electrons.

Fully quantum-mechanical calculations have been performed to determine the radiative collisional cross sections for quenching of metastable muonic hydrogen $p{\mu }^{-}\mathrm{}\left(2s\right)\mathrm{}$ by normal hydrogen atoms and for quenching of the metastable muonic helium ion $\alpha {\mu }^{-}\mathrm{}\left(2s\right)\mathrm{}$ by normal helium atoms. The interatomic potential curves and the radiative transition rates for the mixed electronic-muonic systems are calculated using molecular-structure methods. The nuclear motion is treated as adiabatic and the interaction is written in terms of a complex potential. The cross sections are evaluated by direct numerical integration of the Schrödinger equation. The two-body thermal (300 K) quenching rate constants obtained are 3.7×${10}^{-13\mathrm{}}$ ${\mathrm{cm}}^3$/sec for $p{\mu }^{-}$ and 6.0×${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^3$/sec for $\alpha {\mu }^{-}$.

The photoionization cross section for the two highest-lying orbitals of hydrogen fluoride has been calculated both using a single-center spherical-wave approximation for the continuum electrons and using Tchebychev moment-analysis calculations. The results from the two computational schemes are in good agreement for channels where there is small possibility of partial waves of different $l$ quantum numbers being mixed. Where such mixing can take place, inadequacies of the spherical-wave approach show up as large discrepancies between results calculated using the length and the velocity forms of the transition operator.

Absolute photodetachment cross sections for ${\mathrm{He}}^{-}{}_{}{}^4{}_{}{}^{}P_{}^o{}_{}{}^{}$ have been obtained at discrete photon energies between 0.12 and 4.0 eV by normalizing the He photodetachment products from a 1.3-keV ${\mathrm{He}}^{-}$ beam to those from autodetachment over a known path length, and making use of the known metastable lifetimes. The cross section reaches 1.2×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at 0.12 eV (40 meV above threshold), falls to 1×${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$ at 4.0 eV, and exhibits several distinct features associated with excited He product states.

Based on standard transport theory for the slowing down of heavy ions in matter, a fast and efficient method has been developed for the calculation of range-distribution parameters. The method allows for the use of arbitrary nuclear-scattering cross sections and electronic energy-loss functions, and all target-ion combinations can be handled. Examples of calculations of the mean projected ranges and the longitudinal- and transverse-range stragglings for high-energy heavy ions are presented. The results are compared with existing experimental data.

Measurements of range of 600 MeV/amu ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ in a variety of absorbers have been made to test the accuracy of the higher-order Mott, Bloch, and polarization correction terms to the Bethe expression of stopping power. These corrections give an acceptable ($<2\mathrm{}\sigma$) fit to energies determined by time-of-flight methods. A dramatically improved ($<1\mathrm{}\sigma$) fit follows if the relativistic Bloch term has half its currently calculated magnitude.

The collision-induced light scattering of argon has been measured as a function of density in the gas phase up to 530 amagat at room temperature and in the liquid phase near the triple point. The present measurement of the integrated intensity near the triple point is in strong disagreement with the previous result of Fleury and McTague and is much closer (within a factor of 1.5) to the molecular-dynamics calculations of Alder, Weiss, and Strauss. When the interaction function for collision-induced anisotropy, which accounts well for the results of the dilute-gas experiment, was used in the molecular-dynamics calculations the agreement between the calculated and measured integrated intensity at the triple point was found to be within the experimental error. It is concluded that the effect on the intensity of higher-order terms (i.e., other than the double-double scattering) cannot account for more than ≃ 10% of the total integrated intensity of argon.

An approximate scaling formula has been determined that permits the rapid estimation of cross sections for angular-momentum-changing collisions of Rydberg atoms with a variety of targets, using information about low-energy-electron scattering from the target. The formula is obtained by fitting the results of coupled-channel and Born-approximation calculations to functions of reduced parameters. Application to $\mathrm{Na}\mathrm{}\left(\mathrm{nd}\right)\mathrm{}$ + He, Ne, Ar, ${\mathrm{N}}_2$, C${\mathrm{H}}_4$, ${\mathrm{C}}_3$${\mathrm{H}}_8$; $\mathrm{Rb}\mathrm{}\left(\mathrm{nf}\right)\mathrm{}$ + He, Ar, Xe; and $\mathrm{Xe}\mathrm{}\left(\mathrm{nf}\right)\mathrm{}$ + C${\mathrm{O}}_2$, suggests that the accuracy is about a factor of 2.

Systematics of the atomic properties named in the title and of other related quantities have been comprehensively studied. Our calculations are based on a single-electron approximation using the Hartree-Slater central potential—a model that represents a reasonable compromise between two goals, namely, a realistic description of the major features of atomic dynamics and an economical computation necessary for a survey over many atoms. Our results not only quantify the general trends of the atomic properties as qualitatively expected from the periodic table, but also provide a sensible guide to experiment (on atoms for which no other data are available), to theory (for which we suggest several specific aims of more advanced analysis), and to applications including radiological physics and charged-particle microscopy.

A hole-particle version of the unitary group approach to the many-electron correlation problem is given. To achieve a unique state labeling, the subgroup chain of Flores and Moshinsky for the nuclear many-body problem is modified, and the rules for the construction of relevant irreducible representations and of the orthonormal spinadapted states are given. The structure of these hole-particle formalism spin-adapted bases is illustrated on several examples for all the three possible types of the hole-particle defect pertaining to the excitation, electron attachment, or detachment processes relative to the reference state used. The tensor character of the particle formalism electron-number-preserving generators is pointed out, and their basic classification in the hole-particle formalism is given.

Graphical methods of spin algebras are used to derive the expressions for the matrix elements of the total particle-number-conserving operators in the basis of hole-particle states, adapted to the chain $\mathrm{U}(n^{\prime }+n^{\prime \prime })\supset \mathrm{U}\left(n^{\prime }\right)\otimes \mathrm{U}\left(n^{\prime \prime }\right)$, where $n^{\prime }$ and $n^{\prime \prime }$ designate dimensions of particle and hole subspaces, respectively. The matrix elements are expressed as a product of segment values, each associated with one orbital level as in the particle formalism, and of an additional segment value, representing a linkage of the hole and particle subspaces. It is shown that the particle formalism segment values can be used throughout except for the link segment, whose possible values are derived. An example of hole-particle bases and of their graphical representations is given and the advantages of the hole-particle formalism in shell-model calculations are outlined. An extension of this formalism to particle-number-nonconserving operators, needed in applications involving the $m\mathrm{p}-n\mathrm{h}$ propagators with $m\ne n$, $m$, $n=0\mathrm{}$, 1, and 2, is discussed.

By using the expansion method, the multiconfiguration relativistic Hartree-Fock-Roothaan theory for atomic systems is presented. The matrix element for two-electron operators, such as $\frac{1}{r_{12}}$ or the Breit operator, is calculated by using tensor-recoupling-transformation techniques for the second-quantized operators. The theory is tested in the calculation of term energies for oxygenlike atomic systems (O, ${\mathrm{Fe}}^{18+}$, and ${\mathrm{Hg}}^{72+}$) and transition frequencies for $K$-hole states in ${\mathrm{Fe}}^{18+}$. It is shown that calculated term energies and transition frequencies agree well with experiment. The role of the electron correlation effects and the relativistic effects in each system is also discussed.

We have extended our calculations of Sternheimer shielding functions of Ref. 1 by introducing exchange terms via the self-consistent Hartree-Fock perturbation method. This procedure becomes relatively time consuming. It takes for ${\mathrm{Pr}}^{3+}$ 2-1/2 h of CPU time at a TR 440 computer to achieve convergency after 10 iterations. In addition to the accurate method we have also studied an approximate version, which handles the calculation of exchange integrals in a simplified form so as to make the computational procedure very fast. The approximations inherent to this procedure, however, yield unreliable results, unless the wave functions are considerably contracted. Our results from the accurate method are compared with values reported in the literature, which also take consistency, exchange, and correlation effects into account. We conclude from our study that consistency effects in deriving Sternheimer corrections are dominant over correlation effects.