Thin solid Cu targets were bombarded with Cl ions at incident energies of 40, 50, and 60 MeV. The target $K$ x-ray yields were measured as a function of target thickness. The yield of the Cu target $K$ x rays per scattered projectile increases exponentially with target thickness for all incident Cl charge states from 7+ to 15+ and decreases exponentially with target thickness for the incident Cl charge state 16+. A model calculation which contains the probability for a $K$ vacancy in the projectile as a function of its depth in the target describes the observed behavior. A factor of 8 variation in the Cu $K$ x-ray yield per scattered projectile was observed depending on how the beam was prepared and on what thickness target was used.

In the first paper of this series a formal theory of atomic scattering of electrons in the presence of an intense electromagnetic field was given. Cross sections, near the forward direction, between atomic states (modified by the laser) were obtained. However, it was assumed that the atom could not emit spontaneous radiation. In this paper the effect of spontaneous radiation is included, and it is shown that in most cases the measured cross section will be a weighted average of the two different cross sections starting from the two different initial states which are those atomic states resonantly linked by the laser. The Born approximation for the scattering is obtained, and it is shown that for the simplest description of the spontaneous radiation field the effect of the laser on the cross sections is simply to multiply them by a factor which depends upon the laser detuning.

We report experimental measurements of electron scattering by xenon atoms for various values of impact energy (15 to 450 eV) and scattering angle (0° to 90°). The intensities of the peaks in the energy-loss spectra have been used to evaluate the relative values of the effective and generalized oscillator strengths of the strongest transitions between the ground state of that atom and its excited states lying below the ionization threshold. Furthermore, the absolute values of the optical oscillator strengths, for most of the observed transitions, have been determined from the experimental data.

A theory for the collisional angular-momentum mixing of the Rydberg states of sodium atoms in rare gases is presented. The theory involves a coupled-state calculation based on a pseudopotential interaction between the valence alkali-metal electron and the rare-gas atom. The theory is in good agreement with experiment.

Low-energy rotational-excitation cross sections have been calculated for collisions between ground-state helium atoms and the diatomic molecules HCl, DCl, DF, and HF from model-potential surfaces. Solutions of the coupled radial equations are obtained in the close-coupling coupled-channels (CC) formulation and the $j_z$ conserving coupled-states (CS) approximation, including as many channels (open and closed) as needed for convergence. Trends in the behavior of the cross sections with respect to variations in the potential surface and the spacing of rotational levels are discussed with particular emphasis on the isotope effects. In addition, cross sections calculated for various CS approximations are compared with CC results and comment is made on the influence of the closed channels.

A five-state close-coupling approximation in which $1s$, $2s$, and $2p$ eigenstates and $\overline{3s}$ and $\overline{3p}$ pseudostates of ${\mathrm{He}}^{+}$ are included in the expansion, is used to calculate $1s\to 2s$ and $1s\to 2p$ excitation of ${\mathrm{He}}^{+}$ by electron impact in the intermediate energy range up to about three times ionization threshold energy. Pseudostates are chosen to maximize their overlap with bound states and low-lying continuum states of the same symmetry. Present results for $1s\to 2s$ excitation provide a link between accurate low- and high-energy results and agree with experiment above 70 eV.

The number density of the ions present during the afterglow period of plasmas produced in krypton-nitrogen mixtures was studied for gas pressures ranging from 0.5 to 10 Torr and nitrogen concentrations from 0.05% to 99.95%. Eight ions were detected (${\mathrm{N}}^{+}$, ${\mathrm{N}}_2^{+}$, ${\mathrm{N}}_3^{+}$, ${\mathrm{N}}_4^{+}$, ${\mathrm{Kr}}^{+}$, Kr${\mathrm{N}}^{+}$, Kr${\mathrm{N}}_2^{+}$, ${\mathrm{Kr}}_2^{+}$) although not all were present simultaneously at any given concentration or pressure. At nitrogen percentages between 0.05% and 0.5%, the types of ions present in the afterglow period and their temporal behavior are nearly identical to those in pure-krypton afterglows. At nitrogen concentrations between 0.5% and 2%, there are three ions present: ${\mathrm{Kr}}^{+}$, Kr${\mathrm{N}}^{+}$, and ${\mathrm{Kr}}_2^{+}$. Kr${\mathrm{N}}^{+}$ is produced by the reaction ${\mathrm{Kr}}_2^{+}$ + N → Kr${\mathrm{N}}^{+}$ + Kr, while it is converted to ${\mathrm{Kr}}^{+}$ by the reaction Kr${\mathrm{N}}^{+}$ + N → ${\mathrm{Kr}}^{+}$ + ${\mathrm{N}}_2$. Finally, at very large nitrogen concentrations (99.95%) the following ions are found: ${\mathrm{N}}^{+}$, ${\mathrm{N}}_2^{+}$, ${\mathrm{N}}_3^{+}$, ${\mathrm{N}}_4^{+}$, ${\mathrm{Kr}}^{+}$, a small density of ${\mathrm{Kr}}_2^{+}$, and the previously undetected Kr${\mathrm{N}}_2^{+}$ ion. All of the ions disappear rapidly during the afterglow as could be expected for an average electron energy greater than the thermal energy.

Absolute carbon $K$ x-ray production cross sections (${\sigma }_{K\mathrm{x}}$) have been measured for 0.29-16.0-MeV protons on thin carbon foils, covering the region below the maximum in ${\sigma }_{K\mathrm{x}}$ up to the high-velocity region described by asymptotic (Bethe) theory. An experimental fluorescence yield value ${\omega }_K=(2.46\mathrm{}\pm 0.35)\times {10}^{-3\mathrm{}}$ was determined for carbon. Experimental values of ${\sigma }_K$ are compared to the BEA, SCA, PWBA, and asymptotic theory predictions. At energies close to the maximum in ${\sigma }_K$ (∼0.5 MeV) the BEA predictions were in good agreement with experiment, while at higher energies the PWBA predictions gave the best agreement. Predictions of asymptotic theory lay somewhat below experiment. The measurements show the predicted $\frac{\left(\ln E\right)}{E}$ dependence at higher energies, and experimental values for the two main parameters of the asymptotic theory, viz., $M_{\mathrm{tot}}^2=0.87\mathrm{}$ and $C_{\mathrm{tot}}=8.5\mathrm{}$ (both ± 20%) were derived from a fit to the data. These values are the first of their kind determined by ion bombardment.

The differential cross sections for excitation of the $n=2\mathrm{}$ state of atomic hydrogen by the impact of electrons with energies of 54, 100, 136, and 200 eV are calculated in the distorted-wave approximation with exchange included. Cross sections for excitation of the $2s_{\frac{1}{2}}$, $2p_{\frac{1}{2}}$, and $2p_{\frac{3}{2}}$ states are calculated and summed to give the $n=2\mathrm{}$ differential cross sections. The results of this calculation are compared with previous theoretical calculations and with recent absolute experimental data.

Auger-electron spectroscopy has been used to study inner-shell ionization in Ne, ${\mathrm{N}}_2$, and S${\mathrm{F}}_6$ by 1-5-MeV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ ions. Comparisons are made with corrected plane-wave. Born approximation (CPWBA) and binary-encounter approximation (BEA) calculations. Multiple ionization effects in ${\mathrm{N}}_2$ have been analyzed, and substantial differences in equal-velocity ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ bombardment are shown.

It is shown that the angular distribution of molecular photofragments produced on absorption of polarized light by a mixture of randomly oriented dextrorotatory and levorotatory optical isomers contains an anomalous term due to the presence of unequal numbers of each isomer. The effect is closely related to the forward-backward dissymmetry discovered recently in the angular distribution of photoelectrons ejected from a sample of optically active molecules or molecular negative ions. All terms in the angular distribution are of order $\alpha$, and previous analysis of the photoelectron angular distribution has shown that the anomalous term can be comparable in magnitude to the ordinary terms.

Calculations, including spin-orbit interaction, were performed for the ${\mathrm{}\left(2p\right)\mathrm{}}^5\mathrm{}\left(3s\right)\mathrm{}\left(\mathrm{nl}\right)\mathrm{}$ Auger spectra of Na and Mg, and compared with recent measurements. For these elements it was found that spin-orbit interaction cannot be neglected, that the statistical hypothesis for the population of terms involving inner-shell vacancies arising in ion-atom collisions is poor in relating terms of different configurations, and erratic for terms in a single configuration, and that, while some terms are calculated to have an Auger yield significantly less than unity, the available experimental data lack sufficient resolution to address this question. In comparing calculations and experiment for the Auger spectra resulting from protons incident on Na, agreement was found only by postulating a ${\mathrm{}\left(2s\right)\mathrm{}}^1{\mathrm{}\left(2p\right)\mathrm{}}^6{\mathrm{}\left(4s\right)\mathrm{}}^1$ configuration at 79.0 eV and a ${\mathrm{}\left(2s\right)\mathrm{}}^2{\mathrm{}\left(2p\right)\mathrm{}}^4{\mathrm{}\left(3s\right)\mathrm{}}^2{}_{}{}^1{}_{}{}^{}S$ term at 81.1 eV above the ground state in Na.

In connection with experiments which have been carried out and are planned, we have calculated the violation of parity conservation due to neutral weak currents for transitions to the first excited states of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. A Green's-function technique is used to evaluate the parity-nonconserving transition matrix. The dependence of the results on various input data (e.g., the Weinberg angle) is discussed.

The angular correlation between ionizing and fluorescent x rays is calculated including the dependence on the linear polarization of either x ray. The calculation is done relativistically including all the radiation multipoles using single-particle wave functions calculated in the Hartree-Slater model. The results are given for the ionization of a $2p_{\frac{3}{2}}$ electron with the subsequent filling by a $n=3\mathrm{}$ electron for $Z=30,79 \mathrm{and} 92$.

The collisional self-broadening and shift of neutral argon spectral lines have been determined as a function of atom density $N$ for several lines terminating on either the lower resonance or lower metastable levels. The lines were emitted by a variable-pressure discharge tube equipped with intracapillary thermocouples, and were observed using a pressure-scanned Fabry-Perot interferometer. The line profiles were analyzed using a least-squares fit of Whiting's Voigt function to all profile intensity points. Particular attention was given to the determination of the gas temperature, from which $N$ was calculated. The contribution of nonresonant interactions to the broadening and shift of lines connected to the ground state via resonant transitions was examined using the analysis of Lewis.

Using the results of an analytic perturbation theory for screened Coulomb wave functions, closed-form expressions are given for screened $K$- and $L$-shell photoeffect total cross sections in the nonrelativistic dipole approximation. The analytic results agree very well with numerical dipole calculations for the same potential. These nonrelativistic dipole results are then compared with the full relativistic (including retardation) screened calculations of Scofield. Because of strong cancellations between relativistic and multipole effects, the nonrelativistic dipole results can be shown to yield accurate predictions for the photoeffect for photon energies ranging from threshold to nearly 100 keV.

We have developed a new technique (utilizing inelastic electron tunneling spectroscopy) for the study of changes in molecular structure due to 30-keV electron irradiation. Analysis and interpretation of our experiments is done through the following: (1) an algorithm for fitting observed spectra with a series of fundamental peaks and thereby quantitatively provides the actual intensity of each peak; (2) a theory that determines the total (primary and secondary) electron fluence in the vicinity of the molecules and through the use of theoretical dissociation cross sections provides estimates of effective dissociation cross sections. Thus contributions of various molecular and geometrical properties to the degradation process can be delineated. Experimental data for $\beta -D-\mathrm{fructose}$ reveals that CH, ${\mathrm{CH}}_2$ bonds are less susceptible to molecular degradation than the bonds in the COH functional group; also double bonds are formed. The strength and limitation of this technique are discussed.

The Stark-broadened profiles of the 1640- and 4686-Å lines of ionized helium have been calculated using an approximation to the electron broadening operator in the unified classical-path theory of Smith, Vidal, and Cooper. The approximation is such that the results reproduce the time-ordered impact-theory results in the line center, and the ionized-radiator quasistatic results in the far wings. Sample calculations at $n_e={10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$ and $T=40\mathrm{}000$ °K are found to give significantly more narrow profiles than the corresponding modified-impact-theory results because of a different treatment of the lower-state interaction. Indirect comparison with experiment indicates that the calculated lines are too narrow, but it is expected that the inclusion of neglected effects of ion dynamics and inelastic collisions would improve agreement.

For a multilevel atom or molecule irradiated by a finite superposition of monochromatic fields, the time-dependent rotating-wave-approximation Schrödinger equation can be reduced to an eigenvalue problem when the detunings satisfy a consistency condition. This condition is analyzed and the reduction performed using a graph associated with the interaction Hamiltonian.

We have measured ClVI, Cl VII, and Ar VII, Ar VIII decay times at wavelengths in the range 50-550 Å using the beam-foil technique. The detection system was developed to obtain a spatial resolution of about 50 μm along the beam, allowing very short lifetimes of the order of a few picoseconds to be measured. Our results are compared with recent theoretical results and other experimental data in the Mg I and Na I isoelectronic sequences.