Near-Threshold Electron-Molecule Scattering

Electron induced chemistry of thioformaldehyde

A comprehensive theoretical study was carried out for electron interactions with thioformaldehyde (H₂CS) over a wide range of impact energies (0.01 eV to 5000 eV).

Electron induced chemistry for acetaldehyde

A detailed theoretical study is carried out for electron interactions with acetaldehyde (CH₃CHO) with impact energies ranging from 0.01 to 5000 eV.

Importance of nonresonant scattering in low-energy dissociative electron attachment to molecular hydrogen

A central premise of nearly all theories of dissociative electron attachment is that this process is resonance driven. Neglect of nonresonant scattering, although appropriate for electron-molecule systems with narrow (long-lived) resonances, is problematic for the e-H2 system, which has one of the broadest known resonances. Using the nonadiabatic phase-matrix method we have found that at energies from threshold to 6 eV contributions from nonresonant scattering to cross sections to dissociative attachment to in its ground vibrational and electronic state exceed 60%. Comparison of theoretical and experimental cross sections argue strongly for further efforts to resolve the considerable remaining discrepancies over this most elementary rearrangement process.

Intersections of potential energy surfaces of short-lived states: The complex analogue of conical intersections

Whereas conical intersections between potential energy surfaces of bound states are well known, the interaction of short-lived states has been investigated only rarely. Here, we present several systematically constructed model Hamiltonians to study the topology of intersecting complex potential energy surfaces describing short-lived states: We find the general phenomenon of doubly intersecting complex energy surfaces, i.e., there are two points instead of one as in the case of bound states where the potential energy surfaces coalesce. In addition, seams of intersections of the respective real and imaginary parts of the potential energy surfaces emanate from these two points. Using the Sigma* and Pi* resonance states of the chloroethene anion as a practical example, we demonstrate that our complete linear model Hamiltonian is able to reproduce all phenomena found in explicitly calculated ab initio complex potential energy surfaces.

Jahn-Teller effect for short-lived states: Study of the complex potential energy surfaces

The Jahn-Teller effect for bound electronic states has been investigated for many decades. In contrast, nothing is known regarding its occurrence for short-lived electronic states. Here we investigate the linear and the quadratic E multiply x e Jahn-Teller effect for degenerate resonance states with special regard to the complex potential energy surfaces. We find many new phenomena for both the real and imaginary parts of the potential energy surfaces including additional minima and intersections. Possible simplifications of the equations describing the adiabatic potential energy surfaces are discussed. We also briefly investigate other Jahn-Teller effects in linear approximation. The theoretical concepts are exemplified by calculating ab initio data for the degenerate Pi(*)-type resonance states of the tris(boramethyl)amin anion along two different doubly degenerate vibrational modes.

Scattering resonances in the simplest chemical reaction

Recent studies of state-resolved angular distributions show the participation of reactive scattering resonances in the simplest chemical reaction. This review is intended for those who wish to learn about the state-of-the-art in the study of the H + H2 reaction family that has made this breakthrough possible. This review is also intended for those who wish to gain insight into the nature of reactive scattering resonances. Following a tour across several fields of physics and chemistry where the concept of resonance has been crucial for the understanding of new phenomena, we offer an operational definition and taxonomy of reactive scattering resonances. We introduce simple intuitive models to illustrate each resonance type. We focus next on the last decade of H + H2 reaction dynamics. Emphasis is placed on the various experimental approaches that have been applied to the search for resonance behavior in the H + H2 reaction family. We conclude by sketching the road ahead in the study of H + H2 reactive scattering resonances.