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Toward the end of his career, Zewail developed strong interest in fast electron spectroscopy and imaging, a field to which he made important contributions toward his aim of making molecular movies free of radiation damage. We therefore compare here the atomistic mechanisms leading to destruction of protein samples in diffract-and-destroy experiments for the cases of high-energy electron beam irradiation and X-ray laser pulses. The damage processes and their time-scales are compared and relevant elastic, inelastic, and photoelectron cross sections are given. Inelastic mean-free paths for ejected electrons at very low energies in insulators are compared with the bioparticle size. The dose rate and structural damage rate for electrons are found to be much lower, allowing longer pulses, reduced beam current, and Coulomb interactions for the formation of smaller probes. High-angle electron scattering from the nucleus, which has no parallel in the X-ray case, tracks the slowly moving nuclei during the explosion, just as the gain of the XFEL (X-ray free-electron laser) has no parallel in the electron case. Despite reduced damage and much larger elastic scattering cross sections in the electron case, leading to not dissimilar elastic scattering rates (when account is taken of the greatly increased incident XFEL fluence), progress for single-particle electron diffraction is seen to depend on the effort to reduce emittance growth due to Coulomb interactions, and so allow formation of intense sub-micron beams no larger than a virus.
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Molecular collisions, photoionization and dynamics: honoring Professor Vincent McKoy M. H. F. Bettega, S. J. Buckman, M. Khakoo, P. Limão-Vieira and M. T. do N. Varella, EPJD, 76:65 (2022). https://doi.org/10.1140/epjd/s10053-022-00391-w
The topical issue “Advances on Molecular Collisions, Photoionization and Dynamics” encompasses a set of theoretical and experimental contributions honouring the unprecedented scientific career of our loyal colleague and trusted friend the late Professor Vincent McKoy. He has been a pioneer in implementing ab initio electron-molecule scattering and molecular photoionization theoretical methods, alongside with his collaborations across the globe, having contributed to different research fields that are now well-established and where he leaves a strong scientific legacy as noted by the testimony of his long-lasting collaborator, Carl Winstead. The contributions hereafter are related to the most recent achievements in electron interactions with molecules and molecular ions as a function of phase and stage of aggregation as well as key aspects of photoionization mechanisms therein. Particular topics include studies of photon and electron interactions (excitation, ionization and attachment) with biological, technological, astrophysical and aeronomic relevant molecules, electron transport phenomena and electron induced surface chemistry. Theoretical aspects of model potentials and molecular processes including nonadiabatic chemical reactions are also addressed in this special occasion.
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- Award ID(s):
- 1911702
- PAR ID:
- 10389155
- Date Published:
- Journal Name:
- The European physical journal D Atomic molecular and optical physics
- Volume:
- 76
- Issue:
- 65
- ISSN:
- 1434-6060
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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