A measurement of the cross section for K-shell ionization by 10- and 20-MeV electrons in Mg and Al has been made. These results, together with previous measurements at 50 MeV by Hoffmann et al. and at 70 and 230 MeV by Kamiya et al., allow the increase of the cross section with energy to be defined. The results are found to support the claim of a density effect by Kamiya et al., although the extent of the saturation is not as pronounced as first believed.

Accurate electron-impact differential cross sections for various optically forbidden transitions in Cu i, Mg ii, and Zn ii are used to calculate apparent generalized oscillator strengths (GOS’s) in the electron-impact energy range 15≤E≤100 eV. Most curves of the GOS versus momentum transfer squared, $K^2$, appear compatible with the Lassettre-limit theorem. Extrapolation to the optical oscillator strength values is meaningless for the 15-eV curves of Mg ii and Zn ii for which the unphysical region is significant. The GOS minima, where they exist, near $K^2$→0 are extremely important in assessing whether a given transition is interpretable in terms of the Born approximation.

The difference between the double-ionization cross sections of antiprotons and protons colliding with helium may be explained by the distortion of the two-electron wave function during the collision. The distortion is related to the presence of electron-electron correlations and depends on the sign of the projectile charge. The proposed correlation effect requires an at-least-partly-adiabatic behavior for target electrons. The existence of adiabaticity in high-energy large-impact-parameter collisions is discussed. By building in the effect of distortion into the center-of-charge interaction formulation of the independent-particle model, the calculated cross sections are in agreement with the experimental values.

The angle-dependent post-collision-interaction line-shape formula of Kuchiev and Sheinerman is analyzed and applied to the Xe $N_5$-$O_2$,3${\mathrm{O}}_2$,3 transition. The general formula is adapted to describe an Auger line shape resulting from the radiationless decay of an atom following photoionization. Factors to be considered in comparing theory with proposed experiments are discussed; the range of validity of the theory is considered.

The theory of two-photon ionization of a hydrogenic state in the nonrelativistic dipole approximation is generalized for elliptically polarized light. An application to the metastable 2S state of atomic hydrogen is made. Significant differences in the angular distribution of the outgoing electrons are found depending upon the polarization of the photons. It is claimed that two-photon ionization employing elliptically polarized photons from lasers may provide an additional test for the theories of multiphoton ionization.

Numerical orbital coupled-cluster calculations on the FH molecule are reported, which obtain 99% of the possible correlation energy. Instead of requiring explicit $r_{12}$ functions, it is demonstrated that a one-particle but very well-chosen numerical orbital basis set is adequate to recover essentially all effects of electron correlation. Further reduction of the dimension of the numerical orbital basis set is accomplished via our recently proposed optimized virtual-orbital-space technique. Augmented by the exact second-order energy, the latter allows a reduction to as small as 25% of the original space with no appreciable errors in the correlation energy.

L-subshell-ionization cross sections ${\sigma }_3$/${\sigma }_2$ and ${\sigma }_2$/${\sigma }_1$ for $L_3$, $L_2$, and $L_1$ levels for tungsten have been measured by electron impact at incident electron energies from about one to three times the ionization threshold energy of the $L_1$ subshell. Ionization cross sections for the $L_1$, $L_2$, and $L_3$ levels were deduced from the measured intensity radiations L${\beta }_3$, L${\beta }_1$, and L${\beta }_2$ and using known values for the fluorescence yields, radiative transition probabilities, and Coster-Kronig parameters. The x-ray spectra were obtained with a curved crystal spectrometer (50 cm radius) and recorded on photographic film. Comparison is made with experimental measurements of Chu-Nan Chang and theoretical calculations of Gryzinski and McGuire. A good agreement is achieved for electron-beam energies $E_0$≥1.25 times the energy $E_1$ of $L_1$-level ionization.

The saddle-point complex-rotation method in the intermediate LSJ coupling scheme is used with the Pauli-Breit spin-dependent perturbation operators to compute the spin-induced autoionization rates of the lithiumlike 1s2p2p ${\mathrm{}}^4$$P_J$ states from Z=3 to Z=10. The radiative transition rates of these levels are also calculated in the intermediate LSJ coupling scheme. The combined result yields lifetimes which are compared with the existing experimental and theoretical data in the literature.

We have employed an experimental apparatus in which a sample of nearly ideal, two-level atoms can be exposed to homogeneous amplitude- and phase-controlled resonant laser light to study fundamental dynamical, spectral, and radiative atomic properties. In particular, we show unambiguously that atomic fluorescence is maximized when atoms are purely in their excited state rather than in a superposition of ground and excited state. We also show that fluorescence lifetimes are independent of the atomic excitation level, and finally, we demonstrate interesting correlations between atomic dynamics and atomic spectral features.

Noise spectra of the in-phase and quadrature-phase components of the signal and idler fields of a nondegenerate optical parametric amplifier are calculated. It is shown that, as is suggested by the operator Manley-Rowe relations, the external in-phase (amplitude) fluctuations of the signal and idler fields are correlated in the frequency region lower than the signal and idler cavity bandwidths. If the idler photon flux is continuously measured and the photocurrent fluctuations are fed back to control the pump intensity, the signal output will feature an amplitude noise spectral density reduced to below the standard quantum limit (amplitude squeezing) in the frequency region below the feedback loop and signal and idler cavity bandwidths. An all-optical realization of such a negative-feedback parametric oscillator is presented. It is also shown that a nondegenerate parametric amplifier with idler measurement feedback can add a fixed number of photons to a photon-number state.

An exact expression of the fluorescence spectrum from an interacting lattice system is derived in the weak-field limit. Our model includes a dephasing process. We show that there is no Rayleigh scattering in the direction different from the incoming field due to the phase-matching condition and study the role of the dephasing process.

Preservation of a macroscopic superposition quantum state is achieved in the presence of dissipation when the quantum fluctuations of the heat bath are squeezed. An example is given for a single mode of the electromagnetic field interacting with a squeezed bath. We show that a squeezed bath is more efficient than a thermal or vacuum bath for optical quadrature-phase measurements, and may also be used to prepare states with low quantum noise in one quadrature phase.

We investigate quantum-mechanical second-harmonic generation for parameters such that classical electrodynamics predicts oscillations. Specifically we calculate the Q distribution function in a Gaussian approximation about the classical limit cycle. In the classical limit initial rapid collapse of the Q distribution into the neighborhood of the limit cycle is followed by diffusion around the limit cycle. The experimental significance of this quantum diffusion is discussed.

A detailed presentation of an analytic variational Dirac-Hartree-Fock (VDHF) procedure that avoids the problems of spurious roots and collapse is given. The conditions for the avoidance of spurious roots are discussed, as well as the behavior of the one-electron and total energies as upper bounds under variations of the nonlinear parameters or the dimension of the basis sets. The implementation of the VDHF procedure and the Breit-interaction corrections is presented for Slater-type basis sets, with emphasis on the computational efficiency of the calculations. The Breit-interaction corrections in particular are reviewed in detail. Optimized results are presented for the He, Be, C, and Ne isoelectronic sequences.

We report on an ac-Stark-effect-enhanced wave-mixing experiment in ${\mathrm{I}}_2$ vapor in which an output uv signal at frequency 2${\omega }_1$+${\omega }_2$ is maximized when the input frequencies ${\omega }_1$ and ${\omega }_2$ are both detuned in the same direction from the resonance frequencies of the free molecule. A theory based on a configuration interaction between the ‘‘dressed molecular levels’’ is presented to explain the strong enhancement of the uv signal under these conditions. The data presented demonstrate that tunable coherent radiation at ultraviolet and vacuum-ultraviolet frequencies can be generated by the wave-mixing process we describe.

Ion-channel guiding of an intense relativistic electron beam in a microwave (cm–mm) steady-state free-electron laser (FEL) is proposed. By averaging equations of motion over the high-frequency variation of the radio-frequency field, the expulsion mechanism of plasma electrons is examined and a criterion to allow development of an ion channel in a steady-state FEL is derived. Key issues on FEL operation induced by ion-channel guiding are discussed.

The influence of equilibrium self-field effects on the cyclotron-maser instability is investigated for an intense hollow electron beam, in connection with high-power gyrotron applications. The theoretical analysis is carried out within the framework of the linearized Vlasov-Maxwell equations, assuming that the beam thickness is much less than the mean radius of the beam. The electron orbit is calculated, including the important influence of strong self-fields. The formal dispersion relation for azimuthally symmetric electromagnetic perturbations is obtained. One of the most important features of the analysis is that the radial betatron frequency of an electron, which includes the equilibrium self-field effects, plays a pivotal role in stability behavior. Without ions, it is shown that the radial betatron frequency is always less than the electron cyclotron frequency. In this particular case, any deviation of the betatron frequency from the cyclotron frequency strongly stabilizes the instability. Moreover, it is also found that the self-dielectric effects of a very intense beam is negligibly small. Thus, electromagnetic waves of the vacuum transverse electric waveguide modes are very good approximations for perturbed fields in the cyclotron maser instability.

Numerical calculations have been performed which show the nature of energy coupling between an incident, two-dimensional Gaussian beam at small glancing angle onto the interface between a linear medium and a nonlinear diffusive medium, and a surface wave which can exist at the interface under certain conditions. The coupling is shown to be related to the boundary conditions at the interface that are imposed upon the diffusion equation governing the nonlinearity. This surface wave is postulated as the mechanism which causes the previously unexplained experimental result of ‘‘missing’’ energy in the partially transmissive state of the interface.

The observation of extraordinarily wide wings on the spectrum lines of atomic hydrogen in emission at the cathode surface of an electric discharge is described. Actual line shapes in pure hydrogen manifest an articulation which divides the spectrum line into three distinct regions, each arising from a separate mechanism. Several novel discharge-source configurations have been developed in preceding experimentation, these falling into the general category of hollow cathodes. Three critical experiments have been performed to elucidate the process which gives rise to the extended far wings of the hydrogen lines and to determine their physical point of origin. Ultimately, it is concluded that the cathode surface itself is essential to the mechanism for producing the extreme velocities of the excited atoms which account for the distant extended wings.

Thermal convection is experimentally studied in an annular cell with free-free boundary conditions: A silicon oil floating on mercury and in contact with air. Surface tension forces are comparable to buoyancy forces in driving the convection. The transition to a cellular pattern of rolls is via a forward bifurcation. Above the onset there is a broad band of stable roll patterns differing in their wavelength. Inserting a radial wall in the cell reduces considerably the band of stable patterns and modulates their wavelength.