Photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O−

Oliveira, A. M.; Lehman, Julia H.; McCoy, Anne B.; Lineberger, W. C.

doi:10.1063/1.4963225

Cited by 8 publications

(20 citation statements)

References 51 publications

(66 reference statements)

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“… a Weichman et al b Spin orbit splitting, Brossard et al c Ramond et al d Jin et al e This work. f Oliveira et al …”

Section: Discussionmentioning

confidence: 99%

“…Upon further methyl substitution, forming isopropoxy, the term energy decreases to 68(10) cm –1 . In addition to these examples, the hydroxymethoxy radical (H 2 C(OH)O·) was investigated via anion photoelectron spectroscopy to study the effect of nonalkyl substitution . The hydroxymethoxy term energy was found to be T 0 (Ã ← X̃) ≈ 3300 cm –1 , close to an order of magnitude larger than ethoxy .…”

Section: Introductionmentioning

confidence: 99%

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Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

2018

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We report the photoelectron spectrum of the aminomethoxide anion (HC(NH)O). The electron affinity (EA) of the aminomethoxy radical is determined to be 1.944(1) eV. Transitions to the ground (X̃ A″) and first excited (ÃA') electronic states of aminomethoxy are observed, with the term energy measured to be T(Ã ← X̃) = 0.085(1) eV. A long vibrational progression is observed for the transition to the ground X̃ A″ electronic state of aminomethoxy, primarily consisting of OCN bending and HNH wagging vibrations, leading to the assignment of these two fundamental vibrational frequencies of HC(NH)O· X̃ A″. The gas-phase acidity of aminomethanol is calculated at the G4 level of theory to be Δ H = 374.0 kcal mol, which, when combined with the experimental EA of aminomethoxy in a thermochemical cycle, provides a determination of the O-H bond dissociation energy, D(HC(NH)O-H) as 106(2) kcal mol. Comparisons of the EAs and T(Ã ← X̃) for the aminomethoxy, methoxy, ethoxy, and hydroxymethoxy radicals provides insight into how the substituent group affects the electronic structure of singly substituted alkoxy radicals.

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“… a Weichman et al b Spin orbit splitting, Brossard et al c Ramond et al d Jin et al e This work. f Oliveira et al …”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

2018

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“…Ions generated from expansion of this gas irradiated for different periods of time are included in the Supporting Information. Finally, the isoprene/O 2 /H 2 gas mixture was prepared with 27.5% H 2 , ∼2% O 2 , ∼1% isoprene (Alfa Aesar, 99%), and balance Ar, which generates the oxidizing • OH radical and OH – ions upon passing through the discharge. , To reduce the risk of explosion, we systematically added the reagents (isoprene, then O 2 , buffer Ar, then H 2 , and finally, the remaining Ar) to the electrically grounded tank.…”

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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“…The anion PE imaging apparatus used in this study has been described previously . Ions were generated by coexpanding a mixture of 27.5% H 2 , ∼2% O 2 , ∼1% isoprene, and balance Ar (60 psig) using a pulsed molecular beam valve through a needle electrical discharge, which was stabilized by a hot, biased thoriated iridium ribbon electron emitter. The H 2 /O 2 mixture produces significant quantities of • OH and OH – in the discharge source.…”

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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Photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O−

Cited by 8 publications

References 51 publications

Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

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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Photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O−

Cited by 8 publications

References 51 publications

Photoelectron Spectroscopy of the Aminomethoxide Anion, H2C(NH2)O–

Photoelectron Spectroscopy of the Aminomethoxide Anion, H2C(NH2)O–

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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Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

Photoelectron Spectroscopy of the Aminomethoxide Anion, H₂C(NH₂)O^–

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