David C. Cartwright

Generalized valence bond calculations on the ground state (X 1Σ+g) of nitrogen

Accurate generalized valence bond calculations (GVB) have been carried out on the ground state (Xu20091Σ+g) of the nitrogen molecule for internuclear distances from 0.80 to 5.00 A. For comparative purposes, corresponding Hartree–Fock (HF) and valence bond (VB) calculations are also reported. While accounting for only ∼25% of the correlation energy of N2 at R=Re, the GVB calculations account for ∼80% of the molecular extra correlation energy, and yield a dissociation energy of 8.58 eV (compared to 5.08 eV from the HF corresponding calculations). In addition to considerably improving on the HF and VB descriptions of N2, the GVB wavefunction retains a simple orbital form which is susceptible to analysis in terms of nonclassical, as well as classical, chemical concepts.

Group Theoretical Selection Rules for Electron Impact Spectroscopy.

Abstract Simple group theoretical principles are applied to the consideration of electron scattering off atoms and diatomic and polyatomic molecules. For all scattering angles S g ↔ S u is forbidden for atoms. Fer axial scattering (0° or 180° scattering angle), Σ + ⇹ Σ - for linear polyatomic molecules and S g ⇹ P g ⇹ D g , etc., for atoms. This approach is also used to estimate relative strengths of electron-impact-induced transitions of diatomic and polyatomic molecules.

Electron impact excitation of the Rydberg states in O2 in the 7–10 eV energy‐loss region

Electron impact energy‐loss spectra of O2 in the 7–10 eV region has been investigated at low impact energies and high scattering angles. Under these conditions a number of new transitions have been found which do not appear in optical spectra. Bands at 8.595, 8.826, 9.045, and 9.27 eV have been assigned to the 3sσg 1Π (v′=0, 1, 2, and 3) excitations, respectively, and the idenfification of the corresponding 3Πg bands have been reconfirmed. New transitions appearing at 9.13, 9.32, 9.51, 9.58, and 9.78 eV cannot be unambiguously assigned on the basis of the presently available information.

Transition probabilities for the Meinel band system of N2

Newly measured natural lifetimes for vibrational levels 1–8 and 10 of the Au20092Πu state of N2+ have been analyzed by a weighted, nonlinear, least squares technique to extract the absolute transition moment and its dependence on internuclear distance. Both are considerably different from previous results and lead to different transition probabilities and oscillator strengths. Transition probabilities for both v′=0 and 9 are obtained by interpolation of the ``electronic portion of the band strength and result in predicted values for the lifetimes of the v′=0 and 9 levels.

Decomposition of the photoabsorption Schumann-Runge continuum in O2

The photoabsorption Schumann-Runge continuum in O2 has been decomposed into the contribution from states of both valence and Rydberg character. The decomposition of the experimental photoabsorption (or high-energy, zero-angle, electron energy-loss) data contains contributions from three valence states, four Rydberg states, and one state of unknown character. Information on the perturbed valence-state potential-energy curves in the Franck-Condon region obtained by this analysis substantiate theoretical conclusions of strong valence-Rydberg perturbations in the 8-12 eV excitation region. There is presently no unambiguous identification for the state at 8.93+or-0.04 eV, found in the optical and all the electron energy-loss data.

The importance of polarization for electron scattering in the intermediate energy region

Abstract The angular dependence of electron scattering from the helium atom and the hydrogen molecule for small scattering angles in the 34 – 100 eV impact energy range is explained in terms of the first Born approximation and the polarized Born approximation. The theoretical results compare favorably with the experimental data for both elastic and inelastic scattering. New experimental and theoretical results are presented.