Insight into ethylene interactions with molybdenum suboxide cluster anions from photoelectron spectra of chemifragments

Schaugaard, Richard N.; Topolski, Josey E.; Ray, Manisha; Raghavachari, Krishnan; Jarrold, Caroline Chick

doi:10.1063/1.5008264

Cited by 18 publications

(14 citation statements)

References 53 publications

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“…A more detailed comparison between the computational and experimental results involves a simulation of the vibrational structure of a transition, based on the structures, vibrational frequencies, and normal coordinates of the anion and neutral. A more detailed description of the home-written simulation code was provided previously …”

Section: Methodsmentioning

confidence: 99%

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

et al. 2021

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Evidence of strong photoelectron–valence electron (PEVE) interactions has been observed in the anion photoelectron (PE) spectra of several lanthanide suboxide clusters, which are exceptionally complex from an electronic structure standpoint and are strongly correlated systems. The PE spectrum of Gd2O–, which should have relatively simple electronic structure because of its half-filled 4f subshell, exhibits numerous electronic transitions. The electron affinity determined from the spectrum is 0.26 eV. The intensities of transitions to excited states increase relative to the lower-energy states with lower photon energy, which is consistent with shakeup transitions driven by time-dependent electron–neutral interactions. A group of intense spectral features that lie between electron binding energies of 0.7 and 2.3 eV are assigned to transitions involving detachment of an electron from outer-valence σu and σg orbitals that have large Gd 6s contributions. The spectra show parallel transition manifolds in general, which is consistent with detachment from these orbitals. However, several distinct perpendicular transitions are observed adjacent to several of the vertical transitions. A possible explanation invoking interaction between the ejected electron and the high-spin neutral is proposed. Specifically, the angular momentum of electrons ejected from σu or σg orbitals, which is = 1, can switch to = 0, 2 with an associated change in the Ms of the remnant neutral, which is spin–orbit coupling between a free electron and the spin of a neutral.

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Section: Methodsmentioning

confidence: 99%

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

et al. 2021

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“…65−67 To compare experimental and computational results in more detail in the case of the isoprene/O 2 /H 2 products, simulations were performed using a home-written Franck−Condon simulation code. 69 Vibrational wave functions were approximated as harmonic oscillator wave functions, and the parallel mode approximation was assumed. However, in the cases of m/z 53 and 67, for which the calculations predict large structural differences between the various isomers of the anion and their associated neutrals, along with floppy and therefore anharmonic neutrals, we instead approximated the transition as a Gaussian distribution that is consistent with the calculated ADE and VDE.…”

Section: ■ Methodsmentioning

confidence: 99%

“…To compare experimental and computational results in more detail in the case of the isoprene/O 2 /H 2 products, simulations were performed using a home-written Franck–Condon simulation code . Vibrational wave functions were approximated as harmonic oscillator wave functions, and the parallel mode approximation was assumed.…”

Section: Methodsmentioning

confidence: 99%

Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy

2021

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We present a study on the oxidation of isoprene under several different conditions that may model both atmospheric and combustion chemistry. Anions, formed by passing isoprene/oxidant gas mixtures through a pulsed discharge generating a range of species, are separated via mass spectrometry and characterized by anion photoelectron (PE) spectroscopy supported by computations. Specifically, a UV-irradiated isoprene/O2 mixture, which additionally produces O3, and an isoprene/O2/H2 mixture, which generates •OH when passed through the discharge, were sampled. The mass spectra of ions generated under both conditions show the production of intact molecular ions, ion–molecule complexes (e.g., O2 –, O4 –, and O2 –·isoprene), and singly deprotonated species (e.g., deprotonated isoprene, C5H7 –). In addition, both smaller and oxidized fragments are observed using both gas mixtures, though relative abundances differ. From the UV-irradiated isoprene/O2 gas mixture, additional intact molecular products of reactions initiated by ozonolysis of isoprene, methylglyoxal, and dimethylglyoxal were observed. Fragmentation and oxidation of isoprene observed in both gas mixtures included species with m/z 39, 53, 67, 69, and 83 that we attribute to a series of alkyl- and alkenoxide-based anions. The coexistence of intact molecules and complexes with fragments and reaction products demonstrates the versatility of this ion source as a simple and efficient anion formation method for studying species that may be relevant in atmospheric and combustion chemistry.

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“…We therefore assign band X to the OH − •isoprene IMC. Simulations using spectroscopic parameters calculated from the DFT-optimized IMC and van der Waals complexes were not practical using our own simulation code, 56 which invokes a number of approximations that are valid only for rigid molecules. For the present species, there is a very large difference in intermolecular distances between the two charge states and the change in orientation of the OH relative to isoprene for this system, which makes the assumption of a rigid molecule problematic.…”

Section: ■ Methodsmentioning

confidence: 99%

Emerging Nonvalence Anion States of [Isoprene-H·]·H₂O Accessed via Detachment of OH^–·Isoprene

et al. 2020

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The anion photoelectron imaging spectra of an ion with m/z 85, generated under ion source conditions that optimize •OH production in a coexpansion with isoprene, are presented and analyzed with supporting calculations. A spectroscopic feature observed at a vertical electron detachment energy of 2.45 eV, which dominates the photoelectron spectrum measured at 3.495 eV photon energy, is consistent with the OH–·isoprene ion–molecule complex, while additional signal observed at lower electron binding energy can be attributed to other constitutional isomers. However, spectra measured over a 2.2–2.6 eV photon energy range, i.e., from near threshold of the predominant OH–·isoprene detachment feature through the vertical detachment energy, exhibit sharp features with common electron kinetic energies, suggesting autodetachment from a temporary anion prepared by photoexcitation. The photon energy independence of the electron kinetic energy of these features along with the low dipole moment predicted for the neutral •OH·isoprene van der Waals complex, suggest a complex photon-driven process. We present calculations supporting a hypothesis that near-threshold production of the •OH···isoprene reactive complex results in hydrogen abstraction of the isoprene molecule. The newly formed activated complex anion supports a dipole bound state that temporarily traps the near zero-kinetic energy electron and then autodetaches, encoding the low-frequency modes of the dehydrogenated neutral isoprene radical in the electron kinetic energies.

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Insight into ethylene interactions with molybdenum suboxide cluster anions from photoelectron spectra of chemifragments

Cited by 18 publications

References 53 publications

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy

Emerging Nonvalence Anion States of [Isoprene-H·]·H₂O Accessed via Detachment of OH^–·Isoprene

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Insight into ethylene interactions with molybdenum suboxide cluster anions from photoelectron spectra of chemifragments

Cited by 18 publications

References 53 publications

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd2O–

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd2O–

Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy

Emerging Nonvalence Anion States of [Isoprene-H·]·H2O Accessed via Detachment of OH–·Isoprene

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New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

New Photoelectron–Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd₂O^–

Emerging Nonvalence Anion States of [Isoprene-H·]·H₂O Accessed via Detachment of OH^–·Isoprene