David C. Frost

Bio: David C. Frost is an academic researcher from University of British Columbia. The author has contributed to research in topics: Photoemission spectroscopy & Ionization. The author has an hindex of 27, co-authored 91 publications receiving 2103 citations.

X-ray photoelectron spectra of cobalt compounds

Abstract: The X-ray photoelectron spectra of a variety of cobalt(II) and cobalt(III) complexes have been investigated. Intense satellite lines were observed for the 2p, 3s and 3p peaks in the case of the high spin cobalt(II) compounds, but not for low spin cobalt(III) complexes. The satellites of the 2p levels are best explained as arising from shake-up processes, whereas those of the 3s and 3p levels are thought to arise largely from multiplet (exchange) splitting of the levels. Multiplet splitting of the 2p level is small and responsible for an increase in the doublet separation of the 2p1/2, 2p3/2 spin-orbit levels of the high spin cobalt(II) compounds. The chemical shifts for cobalt differ for the 2p, 3s and 3p levels of the high spin cobalt(II) compounds. Those of the 2p and 3p levels of diamagnetic cobalt(III) and low spin cobalt(II) complexes are equal. The difference in the case of the high spin cobalt(II) compounds is thought to be due to the presence of unpaired 3d electrons.

Photoelectron Kinetic Energy Analysis in Gases by Means of a Spherical Analyser

Abstract: A spherical grid analyser has been used to measure the kinetic energy distribution of photoelectrons produced by the interaction of 584 $\overset{\circ}{\mathrm A}$ radiation with argon, krypton, xenon, hydrogen, HD, deuterium, oxygen and nitrogen. The relative transition probabilities to the $^2$P$\_\frac{3}{2}$ and $^2$P$\_\frac{1}{2}$ levels of the rare gas ions and to various vibronic states of the others are given. A detailed description of the apparatus is included. It is demonstrated that the ionic energy levels measured agree extremely well with those found by optical spectroscopy, and that it will be possible, in favourable cases, to determine the bonding or antibonding nature of an ionized orbital from the shape of the photoelectron stopping curve.

MOPAC: A semiempirical molecular orbital program

Abstract: Before we start, we need a working definition for MOPAC. The following description has been used many times to describe MOPAC: MOPAC is a general-purpose, semiempirical molecular orbital program for the study of chemical reactions involving molecules, ions, and linear polymers. It implements the semiempirical Hamiltonians MNDO, AM 1, MINDO/3, and MNDOPM3, and combir_es the calculations of vibrational spectra, thermodynamic quantities, isotopic substitution effects, and force constants in a fully integrated program. Elements parameterized at the MNDO level include H, Li, Be, B, C, N, O, F, A1, Si, P, S, C1, Ge, Br, Sn, Hg, Pb, and I; at the PM3 level the elements H, C, N, O, F, A1, Si, P, S, C1, Br, and I are available. Within the electronic part of the calculation, molecular and localized orbitals, excited states up to sextets, chemical bond indices, charges, etc. are computed. Both intrinsic and dynamic reaction coordinates can be calculated. A transition-state location routine and two transition-state optimizing routines are available for studying chemical reactions.

Valence bond description of antiferromagnetic coupling in transition metal dimers

Abstract: A single configuration model containing nonorthogonal magnetic orbitals is developed to represent the important features of the antiferromagnetic state of a transition metal dimer. A state of mixed spin symmetry and lowered space symmetry is constructed which has both conceptual and practical computational value. Either unrestricted Hartree–Fock theory or spin polarized density functional theory, e.g., Xα theory, can be used to generate the mixed spin state wave function. The most important consequence of the theory is that the Heisenberg exchange coupling constant J can be calculated simply from the energies of the mixed spin state and the highest pure spin multiplet.

Systematic XPS studies of metal oxides, hydroxides and peroxides

Abstract: The results of a systematic XPS study, under high controlled conditions, of different basic oxides of transition metals, alkali and alkaline-earth metals are presented; the XPS data of some hydroxides and peroxides are also reported. Variations of the O 1s binding energies are analysed and one point of interest is the large binding energy scale obtained for O 1s peaks all associated with a ‘‘2− ’’ formal charge. Through extended Huckel theory-tight binding (EHT-TB) calculations, attempts are made to rationalize the observed variations. The results illustrate the significant differences between real charges on oxygen atoms in transition metal and alkaline-earth oxides.

Multimode molecular dynamics beyond the Born-Oppenheimer approximation

Abstract: Mise au point. Theorie des effets de couplage vibronique multimodes. Probleme a 2 etats. Couplage vibronique mettant en jeu des modes et des etats degeneres. Effets du couplage vibronique multimodes en spectroscopie. Comportement statistique des niveaux d'energie vibroniques. Intersections coniques et evolution temporelle de la fluorescence