Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
The photoionization of enantiomerically pure epichlorohydrin (C(3)H(5)OCl) has been studied using linearly and circularly polarized vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum was recorded and the first three bands assigned using molecular orbital calculations for the expected conformers, although uncertain experimental conformer populations and an anticipated breakdown in Koopmans' theorem leave some ambiguity. Measurements of the photoelectron circular dichroism (PECD) were obtained across a range of photon energies for each of these bands, using electron velocity map imaging to record the angular distributions, during which a record PECD chiral asymmetry factor of 32% was observed. A comparison with calculated PECD curves clarifies the assignment achieved using ionization energies alone and further suggests a likely relative population of the conformers. Threshold photoelectron-photoion coincidence methods were used to study the ionic fragmentation of epichlorohydrin. Fragment ion appearance energies show nonstatistical behavior with clear indications that the cationic epoxide ring is unstable and lower energy decay channels proceeding via ring breaking are generally open. Extensive neutral homochiral clusters of epichlorohydrin may be formed in supersonic molecular beam expansions seeded in Ar. Electron angular distribution measurements made in coincidence with dimer and trimer ions are used to effect an examination of the PECD associated with ionization of size-selected neutral cluster species, and these results differ clearly from PECD of the neutral monomer. The shifted ionization thresholds of the n-mers (n = 2, ..., 7) are shown to follow a simple linear relationship, but under intense beam expansion conditions the monomer deviates from this relationship, and the monomer electron spectra tail to below the expected monomer adiabatic ionization potential (IP). PECD measurements made in coincidence with monomer ions obtained under different beam expansion conditions were used to identify unambiguously a contribution from dissociative photoionization of larger clusters to the monomer parent mass ion yield above and below its adiabatic IP.
The photoionization of enantiomerically pure epichlorohydrin (C(3)H(5)OCl) has been studied using linearly and circularly polarized vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum was recorded and the first three bands assigned using molecular orbital calculations for the expected conformers, although uncertain experimental conformer populations and an anticipated breakdown in Koopmans' theorem leave some ambiguity. Measurements of the photoelectron circular dichroism (PECD) were obtained across a range of photon energies for each of these bands, using electron velocity map imaging to record the angular distributions, during which a record PECD chiral asymmetry factor of 32% was observed. A comparison with calculated PECD curves clarifies the assignment achieved using ionization energies alone and further suggests a likely relative population of the conformers. Threshold photoelectron-photoion coincidence methods were used to study the ionic fragmentation of epichlorohydrin. Fragment ion appearance energies show nonstatistical behavior with clear indications that the cationic epoxide ring is unstable and lower energy decay channels proceeding via ring breaking are generally open. Extensive neutral homochiral clusters of epichlorohydrin may be formed in supersonic molecular beam expansions seeded in Ar. Electron angular distribution measurements made in coincidence with dimer and trimer ions are used to effect an examination of the PECD associated with ionization of size-selected neutral cluster species, and these results differ clearly from PECD of the neutral monomer. The shifted ionization thresholds of the n-mers (n = 2, ..., 7) are shown to follow a simple linear relationship, but under intense beam expansion conditions the monomer deviates from this relationship, and the monomer electron spectra tail to below the expected monomer adiabatic ionization potential (IP). PECD measurements made in coincidence with monomer ions obtained under different beam expansion conditions were used to identify unambiguously a contribution from dissociative photoionization of larger clusters to the monomer parent mass ion yield above and below its adiabatic IP.
We report a first-principles study of the magnetic properties, cation site disorder effect on magnetism and magneto-structural coupling in multiferroic gallium ferrite (GFO) using the local spin density approximation (LSDA+U) of the density functional theory. The calculation of the ground state A-type antiferromagnetic structure predicts magnetic moments consistent with the experiments while consideration of spin-orbit coupling yields a net orbital moment also in good accordance with the experiment. We find that though cation site disorder is not spontaneous in the ground state, interchange between octahedrally coordinated Fe2 and Ga2 sites is most favored in the disordered state. The results show that ferrimagnetism in GFO is primarily due to Ga-Fe site disorder such that Fe spins at Ga1 and Ga2 sites are antiferromagnetically aligned while maintaining ferromagnetic coupling between Fe spins at Ga1 and Fe1 sites as well as between Fe spins at Ga2 and Fe2 sites. Thus we are able to explain the origin of ferrimagnetism in GFO based on cation site disorder. Our calculations, further predict the presence of magneto-structural coupling in GFO which has been recently observed experimentally.
This review examines recent studies of the spectroscopy, dynamics, reactivity and electronic structure of iso-halocarbons, which are isomers of organic halogens that are critically important reactive intermediates in the chemistry of these species. We approach this review from the viewpoint of isomerisation as electron transfer, in as much as the dominant resonance structure of the isomer is an ion pair of halocarbenium ion and halide anion. We show that this perspective is important in understanding the spectroscopy, dynamics and chemical reactivity of the iso-halocarbons. We examine experimental methods for study of the isomer, focusing on the complementary nature of steady state matrix isolation experiments and time-resolved studies, typically carried out in solution. We review experimental data concerning the solvent dependence of the isomer lifetime in solution, examine S N 1 style nucleophilic reactions of the isomer with water and related solvents, discuss the role of the isomer as methylene transfer agent in cyclopropanation reactions and probe the possible role of the isomer in photoinduced halogen exchange. We then discuss the role of the isomer in the gas-phase chemistry and photochemistry of halocarbons, where isomerisation is demonstrated as a path to molecular elimination. Moving beyond the polyhalomethanes, we describe the existence of proton-coupled electron-transfer pathways involving the isomer in the gem-dihaloethanes, examine the potential importance of spin-orbit coupling and the role of triplet states and briefly discuss the potential importance of similar isomeric structures in other organic molecules. We conclude with future perspectives and research on this intriguing class of intermediates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.