Information on the spectrum of oscillator strength for neutral atoms in their ground states is surveyed with particular regard to recent progress in the far uv-soft x-ray range and to the theoretical interpretation of data from experiments and from numerical calculations. The analysis brings out numerous aspects of atomic mechanics and problems that remain unsolved. An effort is made to interconnect different theoretical approaches within the framework of the theory of atomic spectra.

Spectral Distribution of Atomic Oscillator Strengths

Since the appearance of the title paper, a number of new developments have occurred which need to be included in that body of material. We present additional remarks and clarifications which supplement and update numerous aspects of the Bethe theory discussed in the earlier paper. We also bring the bibliography up to date. Plasma stopping power, the ${z}^{3}$ effect, and stopping power for particles at extreme relativistic energies are among the new topics included. We make several comments on Fano's earlier review article, Ann. Rev. Nucl. Sci. 13, 1 (1963).

Inelastic Collisions of Fast Charged Particles with Atoms and Molecules-The Bethe Theory Revisited

In this review we present the energies, configuration, and other properties of resonances (also called "compound states" and "temporary negative ions") in diatomic molecules. Much of the information is presented in the form of tables and energy level diagrams. Vibrational, rotational, and electronic excitation are discussed whenever these processes have given information on resonances; often these excitation processes proceed via resonances. The paper is divided according to molecular species (${\mathrm{H}}_{2}$, ${\mathrm{N}}_{2}$, CO, NO, ${\mathrm{O}}_{2}$), but the main conclusions are discussed by the nature of the processes involved.

Resonances in Electron Impact on Diatomic Molecules

It is shown that a consistent application of the p
1/3 approximation of the Hartree-Fock-Slater method requires the use of one specific procedure, the sum method, for the calculation of the energy E

 1
 of singlet excited states of closed shell molecules. Further, E

 1
 is found to be in reasonable agreement with experiment for a number of molecules, contrary to the energy E

 2
 obtained according to another method discussed in the literature. The calculation of other multiplet splittings than singlet-triplet in the Hartree-Fock-Slater method is also considered.

On the calculation of multiplet energies by the hartree-fock-slater method

Inelastic collisions of fast charged particles with atoms and molecules the Bethe theory revisited

The generalized oscillator strengths for the 61S0→61P1 transition in mercury have been determined at 300‐, 400‐, and 500‐eV electron kinetic energy. Extrapolation to zero momentum change gives f0 = 1.11 ± 0.10. This result is in very good agreement with the optical oscillator strength, f0 = 1.18 ± 0.07, which was determined by Lurio using the zero‐field level crossing method.

Generalized Oscillator Strengths for the 61S0→61P1 Transition in Mercury

Vibrational excitation by electron impact, in the kinetic‐energy range 30–60 eV, has been studied for water vapor and carbon dioxide. Intensities relative to elastic scattering have been determined at scattering angles to 15°. Fundamental vibrations are excited with much greater intensity than either overtones or combination bands, although the latter appear (weakly) in the spectra. Weak scattering in the energy‐loss region 4.5–7.0 eV and its interpretation is discussed.

Excitation by Electron Impact of Vibrational Transitions in Water and Carbon Dioxide at Kinetic Energies between 30 and 60 eV

An electron source is described that provides, by means of an electrostatic velocity analyzer, for velocity selection on an electron beam before scattering. The energy width of the electron beam is sufficiently reduced to resolve the transitions to the 5 1P and 6 1P states in helium. These states are separated by 0.17 V. Relative oscillator strengths for two additional members of the Rydberg series 1 1S→m 1P have been determined by study of the zero angle electron scattering.

Higher-resolution study of the electron-impact spectrum of helium

Generalized oscillator strengths have been determined at 300, 400, and 500 eV for the two transitions B 1Σ+ ← X 1Σ+ and C 1Σ+ ← X 1Σ+ in carbon monoxide The Born approximation does not hold accurately for either transition The largest deviations (percentage wise) are found for the first of the above transitions and the trend of oscillator strength with momentum change (of the colliding electron) is very different from anything previously observed This abnormal behavior is also found in relative intensity measurements done at low kinetic energies (to 23 eV) These transitions were studied because recent experimental and theoretical investigations [J Chem Phys 53, 3801, 3806 (1970)] indicated that deviations from the Born approximation at high kinetic energies are subject to a selection rule; the deviations are maximum when term symbols are the same in ground and excited states Previous experimental tests have been done only on forbidden transitions The experiments reported in the present paper show

New Selection Rule, Illustrated by Collision Cross Section Studies on the B 1Σ+ ← X 1Σ+ and the C 1Σ+ ← X 1Σ+ Transitions in Carbon Monoxide at Kinetic Energies of 300, 400, and 500 eV

Electron‐impact spectra of mercury vapor have been investigated at incident electron energies between 50 and 300 eV. An intensity anomaly (expected from previous studies of atomic spectra) has been observed in the 61S0 → m1P1 series due to a perturbation by the 6p′ 1P state. Relative cross sections and oscillator strengths have been calculated from the intensity data at 300 eV and zero scattering angle.

Ausma Skerbele

Papers

Generalized Oscillator Strengths for the 61S0→61P1 Transition in Mercury

Excitation by Electron Impact of Vibrational Transitions in Water and Carbon Dioxide at Kinetic Energies between 30 and 60 eV

Higher-resolution study of the electron-impact spectrum of helium

New Selection Rule, Illustrated by Collision Cross Section Studies on the B 1Σ+ ← X 1Σ+ and the C 1Σ+ ← X 1Σ+ Transitions in Carbon Monoxide at Kinetic Energies of 300, 400, and 500 eV

Electron-Impact Spectrum of Mercury Vapor