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

An electrostatic lens system which compensates for chromatic aberration has been tested in an electron spectrometer. The results indicate that this lens is suitable for comparisons of peak intensities in electron‐impact spectra. Relative intensities in vibrational progressions that belong to a single electronic transition have been studied in N2, CO, and NH3 and found to be nearly independent of the scattering angle. Electron‐impact spectra have been reported for helium, nitrogen, oxygen, argon, nitric oxide, nitrous oxide, ammonia, water vapor, carbon dioxide, ethylene, acetylene, and benzene at electron kinetic energies between 33 and 100 eV. Spectral regions of special interest are encountered in CO2 and C6H6. At excitation energies of 7–10 eV in CO2 a change in intensity distribution, attributed to transition from an electric‐quadrupole to an electric‐dipole spectrum, is observed as the kinetic energy is raised. In the case of C6H6 a change in the spectrum with angle is encountered which strongly sugg...

HIGH-RESOLUTION STUDY OF ELECTRON-IMPACT SPECTRA AT KINETIC ENERGIES BETWEEN 33 AND 100 eV AND SCATTERING ANGLES TO 16--.

Relative generalized oscillator strengths have been determined for the 11S→21P transition in helium as a function of momentum change of the colliding electron and normalized to the theoretical oscillator strength {calculated by Schiff and Pekeris [Phys Rev 134, A638 (1964) ]} at zero momentum change The validity of the normalizing procedure is investigated theoretically and it is shown that the limit of the generalized oscillator strength at zero momentum change is equal to the optical oscillator strength for any atom or molecule at any incident energy regardless of whether the first Born approximation holds The normalizing procedure is therefore justified The results are compared with the experimental and theoretical oscillator strengths obtained by other investigators The limiting relation for oscillator strengths is established under much more general conditions than in any previous research

Generalized Oscillator Strength for 11S→21P Transition of Helium. Theory of Limiting Oscillator Strengths

Generalized oscillator strengths have been measured for the υ′ = 2 level of the fourth positive bands of carbon monoxide by comparing inelastically and elastically scattered electrons at 300‐, 400‐, and 500‐eV kinetic energy and using the elastic collision cross sections measured by Bromberg [J. Chem. Phys. 52, 1243 (1970)]. Extrapolation to zero momentum change gives f0 = 0.0429. From relative intensity measurements, the limiting oscillator strengths of the levels from υ′ = 0–12 have also been determined. From zero angle spectra, the limiting oscillator strengths for transitions to the B 1Σ+, C 1Σ+, and E 1Π states have been determined. The values are 0.0153 ± 0.0014, 0.163 ± 0.015, and 0.094 ± 0.009, respectively; υ′ = 0 in each case. Relative intensities in the fourth positive bands have also been determined (and redetermined) at various angles and kinetic energies. Possible variation in relative intensities with scattering angle is discussed. A possible reason is given for the large discrepancy (a fac...

Absolute Generalized Oscillator Strengths for Four Electronic Transitions in Carbon Monoxide

An electron spectrometer, which provides velocity selection before scattering, is described; and the results of a study of relative intensities in the carbon monoxide spectrum are reported. The vibrational levels of the fourth positive band system have been resolved and relative intensities determined for the first nine. The relative intensities are compared with calculated Franck—Condon factors. The agreement is good at low vibrational quantum numbers but noticeable discrepancies are found for high‐vibrational levels.The problem of calculating relative oscillator strengths from a fully resolved spectrum is considered and applied to data obtained in the present research. Relative oscillator strengths are compared with those obtained previously from unresolved spectra.If the Born approximation is valid, then the electron‐impact and ultraviolet absorption spectra should be closely similar. This is actually observed for most of the spectrum but the transition at 12.79 V is an outstanding exception. The relat...

Intensity Distribution in the Electron‐Impact Spectrum of Carbon Monoxide at High‐Resolution and Small Scattering Angles

Electron‐impact spectra at zero scattering angle have been obtained for nitrogen, carbon monoxide, water, ammonia, and benzene. Vibrational structure has been resolved for the a 1πg state in nitrogen and two Rydberg transitions in water spectra. The results have been compared with ultraviolet absorption data.

Ausma Skerbele

Papers

HIGH-RESOLUTION STUDY OF ELECTRON-IMPACT SPECTRA AT KINETIC ENERGIES BETWEEN 33 AND 100 eV AND SCATTERING ANGLES TO 16--.

Generalized Oscillator Strength for 11S→21P Transition of Helium. Theory of Limiting Oscillator Strengths

Absolute Generalized Oscillator Strengths for Four Electronic Transitions in Carbon Monoxide

Intensity Distribution in the Electron‐Impact Spectrum of Carbon Monoxide at High‐Resolution and Small Scattering Angles

Electron-impact spectra