Electron-impact scaled collision strengths $Z^2\Omega$ for a large number of inner-shell excitation transitions involving configuration-mixed and/or parentage-mixed upper levels are obtained for lithiumlike ions in the limit $Z\to \infty$. Since this is the simplest case for which both parentage and configuration mixing occur, this problem is of intrinsic interest to the atomic physicist. The results are also expected to be of interest in applications to highly charged lithiumlike ions occurring in high-temperature, low-density plasmas. The effects of mixing are found to be large in several cases. However, as for the unmixed results, the collision strengths can still be expressed in a simple way in terms of the scaled hydrogenic ion collision strengths $Z^2{\Omega }_{\mathrm{H}}$ and $Z^2{\Omega }_{\mathrm{H}}^e$.

The H-Hg total scattering cross section has been measured in the low-energy region (30-1520 ${\mathrm{cm}}^{-1\mathrm{}}$) in which resonance scattering is possible. A resonance observed at the energy of 43.4 ${\mathrm{cm}}^{-1\mathrm{}}$ has been attributed to the molecular state with rotational quantum number $l=9\mathrm{}$ and vibrational quantum number $\nu =3\mathrm{}$. This result provides improved information about the dissociation energy of the H-Hg molecule. The total-cross-section measurements, together with information from the bound states of the three isotopic systems, have been used to determine the potential in the pseudocrossing region. Measurements of the total cross section of the system ${\mathrm{H}}_2$-Hg are also reported.

Total emission cross sections, arising from charge transfer and impact excitation in ${\mathrm{K}}^{+}$ -Ar collisions, have been measured over the laboratory energy range 0.2-3 keV. Regularly spaced oscillatory structure has been observed with a phase-angle difference of 180° between potassium and argon emissions. An analysis of the polarization, based on the double-crossing model and interfering adiabatic states of the ${\mathrm{}\left(\mathrm{KAr}\right)\mathrm{}}^{+}$ quasimolecule, leads to the conclusion that ${}_{}{}^3{}_{}{}^{}\mathrm{II}$ states with the outer (active) electron in a ${}_{}{}^2{}_{}{}^{}\pi$ orbital are primarily responsible for the structure.

The lowest ${}_{}{}^1{}_{}{}^{}S$ resonance in electron-hydrogen scattering has been calculated using a Hylleraas correlation function with up to 95 terms in the optical potential formalism. The results including estimated errors are $E_r=9.55735\mathrm{}\pm 5\times {10}^{-5\mathrm{}}$ eV, ${\Gamma }^{\mathrm{BW}}=0.04717\mathrm{}\pm 2\times {10}^{-5\mathrm{}}$ eV. These results should be useful for experimental calibration purposes; they are compared to previous, calculated and experimental results. The conventional or Breit-Wigner width ${\Gamma }^{\mathrm{BW}}$ above is different from the width which comes naturally out of the Feshbach formalism. A simple formula relating the two is derived.

The Feshbach optical-potential formalism yields resonance parameters which may differ slightly from those usually defined. By employing the definition of resonances in terms of poles of the analytically continued $S$ matrix, corrections are derived which reconcile the two sets of parameters. These corrections are illustrated using a simple, solvable scattering model.

${\mathrm{H}}^{+}$ and ${\mathrm{D}}^{+}$ energy spectra have been obtained using the time-energy spectroscopy technique. Spectra are presented for ${\mathrm{He}}^{+}$ bombarding energies of 0.5, 1, 2, 3, and 4 MeV. The reflection approximation is used to analyze the spectra and determine the relative contribution to the ${\mathrm{H}}^{+}$ and ${\mathrm{D}}^{+}$ yields of the $1s{\sigma }_g$, $2p{\sigma }_u$, $2p{\pi }_u$, $2s{\sigma }_g$, and double-ionization potential curves of the target molecules. Yield observed in the 2- to 4-eV range suggests that states of ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ which autoionize to the dissociative continuum of the ground $1s{\sigma }_g$ state of ${\mathrm{H}}_2^{+}$ and ${\mathrm{D}}_2^{+}$ contribute to the spectra. The yield is dominated by the excitation of the $2p{\sigma }_u$, $2p{\pi }_u$, and double-ionization potential curves.

Angular distributions have been measured for the projectile $K$ x rays emitted by highly ionized ions with $6\le Z\le 9$ incident on helium at MeV/amu energies. Polarization fractions have been determined by analysis of the data to include systematic consideration of the angular-dependent detector efficiency. For incident bare nuclei, a polarization fraction of 24.7 ± 1%, independent of energy and projectile atomic number, was observed for $K$ radiation following electron capture to excited states. With incident one-electron ions, a $Z$-dependent polarization fraction was obtained, reaching a maximum of 40 ± 2% for oxygen ions. Lower-charge-state ions show decreasing values of $P$ and the angular distributions approach isotropy for $K$ x radiation from ${\mathrm{F}}^{+2\mathrm{}}$ ions. For collisions of ${\mathrm{F}}^{+4\mathrm{}}$ ions in argon, the Ar $K$ radiation is isotropic within 2% uncertainty.

Optical emissions produced by collision of 100-eV ${\mathrm{He}}^{+}$ ions with Xe atoms have been studied over the spectral range from 40 to 900 nm. All of the major lines in the emission spectrum can be assigned to transitions in Xeii resulting from charge-transfer reactions. Emission cross sections for the major lines in the vacuum-ultraviolet and visible spectral regions are reported and the importance of cascading is assessed. The kinetic energy dependence is discussed for several of these lines.

The connection between wave functions describing inelastic collisions and a complete set of standing wave functions, expanded in a Born-Oppenheimer-type base, is developed in terms of Jost functions generalized for application to velocity-coupled channels. The Jost functions represent conserved currents which include, in our case, contributions from nuclear motion. Several limiting cases of a recently developed post-adiabatic treatment are examined from the points of view of numerical applications as well as qualitative discussion. The example of a spinning particle traversing a magnetic field of variable direction is worked out.

It is shown through the use of transformation theory that unique semiclassical atomic scattering states which obey the asymptotic conditions of formal scattering theory can be derived by transforming "nontraveling" atomic states, i.e., states whose coordinate variables are referred to a stationary origin, to frames at rest with respect to the incoming or outgoing particles. An overview of the problem of properly defining such scattering states is presented. The operator which carries out the necessary transformation from inertial to noninertial frames is derived and its properties are discussed. The relation of this transformation operator to the "translation factor" discussed in the literature is presented. The application of this operator to transform the time-dependent Schrödinger equation from an inertial to a noninertial frame is presented and shown to introduce new terms in the resulting equation. The implications of these new terms to scattering problems are discussed.

Rydberg-state excitations in ${\mathrm{Ne}}^{+}$, ${\mathrm{Mg}}^{+}$ -He collisions have been studied in the projectile energy range 10-75 keV by means of optical spectrometry in a search for systematic trends. The relative excitation cross sections for levels of a Rydberg-term series are found to follow a general ${\left(n^{*}\right)}^p$ behavior ($n^{*}$ being the effective quantum number) with $p\lesssim -3\mathrm{}$ varying with collision energy and particles, regardless of whether the excited-state population results from direct excitation, single-electron transfer, or double-electron transfer. At higher collision energies $p\simeq -3\mathrm{}$ as predicted by theory. Polarization of the emitted line radiation indicates that there is no general rule for the relative excitation of the different magnetic substates of the same level. A statistical distribution of excitation is found for levels within the same term when the fine-structure splitting is small.

A minimum principle for the calculation of the scattering length, applicable when the ground-state wave function of the target system is known precisely, has been available for some time. When, as is almost always the case, the target wave function is imprecisely known, a minimum principle is available but the simple minimum principle noted above is not applicable. Further, as recent calculations show, numerical instabilities usually arise which severely limit the utility of even an ordinary variational approach. The difficulty, which can be traced to the appearance of singularities in the variational construction, is here removed through the introduction of a minimum principle, not for the true scattering length, but for one associated with a closely connected problem. This guarantees that no instability difficulties can arise as the trial scattering wave function and the trial target wave function are improved. The calculations are little different from those required when the target ground-state wave function is known, and, in fact, the original version of the minimum principle is recovered as the trial target wave function becomes exact. A careful discussion is given of the types of problems to which the method can be applied. In particular, the effects of the Pauli principle, and the existence of a finite number of composite bound states, can be accounted for.

The satellite structure in the valence shell x-ray photoelectron spectrum (XPS) of CO is studied. The configuration interaction method is used to construct correlated many-electron wave functions for the different final states of C${\mathrm{O}}^{+}$. It is found that (1) the conventional shake-up model cannot explain the satellite structure; (2) a considerable amount of intensity is lost from the main, "single-hole," ${}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ states ($3{\sigma }^{-1\mathrm{}}$, $4{\sigma }^{-1\mathrm{}}$, and $5{\sigma }^{-1\mathrm{}}$) due to electron correlation; and (3) the $3{\sigma }^{-1\mathrm{}}$ peak satellites are at lower, rather than higher, binding energy than the main peak. Franck-Condon broadening is estimated and shown to be a major cause of the large width of the observed structures on the high-binding-energy side of the $4{\sigma }^{-1\mathrm{}}$ peak. Our conclusions are supported by the results of other electron spectroscopies in addition to XPS.

Multiphoton ionization of atomic sodium has been studied experimentally for near resonance between the radiation field and several bound-bound transitions of the atom. It has been found that the atom-field interaction must be treated in a highly nonlinear way to describe successfully the observations, even when the absolute spectral power densities are relatively modest. Rabi frequencies as high as 10 GHz are found to be directly observable with simple flashlamp-pumped tunable dye lasers.

We report detailed spectroscopic measurements of light emission and excited level populations in a pure-helium afterglow at a pressure of 2.03 Torr. The free-electron temperature could be varied by microwave heating. Electron density $n_e$ and temperature $T_e$ were measured by precision microwave interferometry and they range from 5 × ${10}^9$ to 3 × ${10}^{11}$ ${\mathrm{cm}}^{-3\mathrm{}}$ for $n_e$ and from 300 to 600°K for $T_e$. Rydberg states of neutral helium near the bottleneck for collisional-radiative (CR) recombination were perturbed in a well-controlled manner by photoionization with 10.6-μm photons. Our experimental data are consistent with a CR recombination scheme with simultaneous stabilization by collisions with free electrons and with neutral helium atoms. They establish the fact that the Gryziński formalism for electron-impact-induced transitions between bound rydberg states of high principal quantum number seriously overestimates the probability of collisions with small energy transfers. This study gives also experimental indications of what appears to be neutral-stabilized CR recombination of an atomic ion, ${\mathrm{He}}^{+}$. The experimental recombination rate coefficient is well represented over the range of parameters covered at 2.03 Torr by $\alpha \left({\mathrm{cm}}^3 invsec\right)=3.5\mathrm{}\times {10}^{-5\mathrm{}}{T}_e^{-1.9\mathrm{}}+6.0\mathrm{}\times {10}^{-9\mathrm{}}{T}_e^{-2.18\mathrm{}}{n_e}^{0.37}+3.8\mathrm{}\times {10}^{-9\mathrm{}}{T}_e^{-4.5\mathrm{}}{n}_e$, in reasonable agreement with available theories.

Two uniform, semiclassical methods are presented for analytically evaluating matrix elements using stationary-phase techniques. The analytic expressions are appropriate for electronic transitions between molecular states that have monotonic difference potentials. Such a situation is encountered in the calculation of the spectra in excimer (e.g., ${\mathrm{Xe}}_2$*) and excimer-like (e.g., RbXe*) vapor systems. One method utilizes uniform JWKB wave functions throughout the analytic evaluation of the matrix elements, while the second uses simple JWKB wave functions that are modified at the end. The first proves to be more accurate for such systems. The uniform nature of its derivation assures its applicability even to transitions that occur near classical turning points. Numerical results are presented for the far red-wing emission spectrum of RbXe, and a detailed interpretive analysis of the undulatory structure is given. Using the uniform-JWKB, stationary-phase approximation, modifications of the $\mathrm{Rb}{\mathrm{Xe}}^{*}\left(A{}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}}^{}{}_{}{}^{}\right)$ potential are suggested based on a comparison of the predicted and experimental spectra.

We have performed infrared spectroscopy on sodium Rydberg levels in an atomic beam. A C${\mathrm{O}}_2$ laser was used to provide narrow linewidths and absolute frequency markers. New results have been obtained for the term energy and for the fine-structure splitting of the $17p$ level.

Measurements of the absolute cross section for the photoionization of cesium atoms near threshold are reported. The results agree well with recent model potential calculations and are approximately a factor of 2 smaller than earlier experimental results.

We have measured the hyperfine structure in many highly-excited $S$ and $P$ states of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$. The results for the magnetic-dipole coupling constants are, in MHz, for ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$: $A\left(10\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=56.3\mathrm{}\left(2\right)\mathrm{}$, $A\left(11\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=37.4\mathrm{}\left(3\right)\mathrm{}$; and for ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$: $A\left(9\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=110.1\mathrm{}\left(5\right)\mathrm{}$, $A\left(13\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=18.4\mathrm{}\left(1\right)\mathrm{}$, $A\left(14\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=13.4\mathrm{}\left(1\right)\mathrm{}$, $A\left(15\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=10.1\mathrm{}\left(1\right)\mathrm{}$, $A\left(16\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=7.73\mathrm{}\left(5\right)\mathrm{}$, $A\left(17\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)=6.06\mathrm{}\left(10\right)\mathrm{}$, $A\left(10\mathrm{}{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)=13.9\mathrm{}\left(2\right)\mathrm{}$.

The radiative corrections to the photoeffect are evaluated for the $K$-shell of hydrogenlike atoms to lowest order in the radiation field. The corrective matrix element is first discussed within the framework of the bound-state interaction (Furry) picture. We then employ the relativistic Born approximation for the Coulomb Dirac propagator and the final continuum wave function of the electron to obtain an expression which is correct to lowest order in $\alpha Z$, provided $\frac{\alpha Z}{\beta }\ll 1$, where $\beta$ is the velocity of the ejected electron. The renormalization program is carried out completely, and the lowest-order radiative corrections are given explicitly in terms of the familiar first-order invariant functions of QED. The matrix element which results is further analyzed in terms of invariant amplitudes which are expressed as sums of Feynman parameter integrals. Finally, we evaluate the differential cross section assuming the polarizations of the electron and photon are not observed. Infrared divergences are eliminated from this cross section by allowing for the possibility that an unobserved soft photon is emitted along with the photoelectron. Although in general a numerical evaluation is necessary, analytic expressions are given for the low- and high-energy limits of our final expression for the radiative corrections to the photoeffect. We find that, while the corrections are small at low energy, for incident photons in the range 1-10 MeV and for electrons emitted near the forward direction (finite momentum transfer), the radiative corrections tend to reduce the photoeffect differential cross section by 1.0 to 7.0%.