Cover Feature: Direct Evidence of the Benzylium and Tropylium Cations as the Two Long‐Lived Isomers of C7H7+ (ChemPhysChem 23/2018)

Jusko, Pavol; Simon, Aude; Banhatti, Shreyak; Brünken, Sandra; Joblin, C.

doi:10.1002/cphc.201801055

Cited by 3 publications

(8 citation statements)

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“…population of the phen 2+ isomer and consequently a change in the peak intensity of phen 2+ bands relative to the anth 2+ bands. This method was successfully implemented for benzylium and tropylium cations (C 7 H 7 + ), two isomers formed in dissociative ionization of toluene (Jusko et al 2018a), but we did not observe any change in the peak intensity for any of the phen 2+ bands. Instead, the intensity of the phen 2+ bands decreased over time during the measurement campaign, leading us to conclude that they are due to contamination instead of isomerization.…”

Section: Anthracenementioning

confidence: 72%

“…To account for fluctuations in the number of complex ions and varying laser energy during the course of a single scan, the spectra were normalized to laser pulse energy and baseline corrected before averaging over multiple scans. Saturation depletion measurements allowed us to decode the isomer ratios of molecular ions having two or more stable structures, see, for example, Jusko et al (2018a). A detailed account of this technique is discussed in Jusko et al (2019).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The five lowest energy conformers were optimized and harmonic vibrational frequencies were calculated (see appendix B.1). Here the dispersion corrected wB97XD functional with a cc-pVTZ basis was used, which was found previously to work well for weaklybound RG-ion complexes (Jusko et al 2018a).…”

Section: Theoretical Methodsmentioning

confidence: 99%

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Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Banhatti

Palotás

Jusko

et al. 2021

A&A

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The so-called aromatic infrared bands (AIBs) are attributed to emission of polycyclic aromatic hydrocarbons (PAHs). The observed variations toward different regions in space are believed to be caused by contributions of different classes of PAH molecules, that is to say with respect to their size, structure, and charge state. Laboratory spectra of members of these classes are needed to compare them to observations and to benchmark quantum-chemically computed spectra of these species. In this paper we present the experimental infrared (IR) spectra of three different PAH dications, naphthalene 2+ , anthracene 2+ , and phenanthrene 2+ , in the vibrational fingerprint region 500-1700 cm −1. The dications were produced by electron impact ionization (EI) of the vapors with 70 eV electrons, and they remained stable against dissociation and Coulomb explosion. The vibrational spectra were obtained by IR predissociation of the PAH 2+ complexed with neon in a 22-pole cryogenic ion trap setup coupled to a free-electron infrared laser at the Free-Electron Lasers for Infrared eXperiments (FELIX) Laboratory. We performed anharmonic density-functional theory (DFT) calculations for both singly and doubly charged states of the three molecules. The experimental band positions showed excellent agreement with the calculated band positions of the singlet electronic ground state for all three doubly charged species, indicating its higher stability over the triplet state. The presence of several strong combination bands and additional weaker features in the recorded spectra, especially in the 10-15 µm region of the mid-IR spectrum, required anharmonic calculations to understand their effects on the total integrated intensity for the different charge states. These measurements, in tandem with theoretical calculations, will help in the identification of this specific class of doubly-charged PAHs as carriers of AIBs.

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Section: Anthracenementioning

confidence: 72%

Section: Experimental Methodsmentioning

confidence: 99%

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Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Banhatti

Palotás

Jusko

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

Section: Experimental Methodsmentioning

confidence: 99%

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Banhatti,

Palotás,

Jusko

et al. 2021

Preprint

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The so-called aromatic infrared bands (AIBs) are attributed to emission of polycyclic aromatic hydrocarbons (PAHs). The observed variations toward different regions in space are believed to be caused by contributions of different classes of PAH molecules, that is to say with respect to their size, structure, and charge state. Laboratory spectra of members of these classes are needed to compare them to observations and to benchmark quantum-chemically computed spectra of these species. In this paper we present the experimental infrared (IR) spectra of three different PAH dications, naphthalene 2+ , anthracene 2+ , and phenanthrene 2+ , in the vibrational fingerprint region 500 -1700 cm −1 . The dications were produced by electron impact ionization (EI) of the vapors with 70 eV electrons, and they remained stable against dissociation and Coulomb explosion. The vibrational spectra were obtained by IR predissociation of the PAH 2+ complexed with neon in a 22-pole cryogenic ion trap setup coupled to a free-electron infrared laser at the Free-Electron Lasers for Infrared eXperiments (FELIX) Laboratory. We performed anharmonic density-functional theory (DFT) calculations for both singly and doubly charged states of the three molecules. The experimental band positions showed excellent agreement with the calculated band positions of the singlet electronic ground state for all three doubly charged species, indicating its higher stability over the triplet state. The presence of several strong combination bands and additional weaker features in the recorded spectra, especially in the 10-15 µm region of the mid-IR spectrum, required anharmonic calculations to understand their effects on the total integrated intensity for the different charge states. These measurements, in tandem with theoretical calculations, will help in the identification of this specific class of doubly-charged PAHs as carriers of AIBs.

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“…In the past, these techniques have been successfully employed to elucidate the isomeric composition of cationic fragmentation products upon dissociative ionization of PAHs and related species. Using IRPD in a cryogenic ion trap, Jusko et al 23 recorded the mid-IR spectra of Ne-tagged C 7 H 7 + and revealed its two isomeric forms, i.e., benzylium + and tropylium + . Ne-tagged doubly dehydrogenated pyrene (ddPy + ) was spectroscopically investigated using the same technique by Panchagnula et al 24 The results showed that its spectral features correspond to a mixture of different isomers (4,5-ddPy + and 1,2-ddPy + ) favoured by the loss of hydrogen from the same aromatic ring.…”

Section: Introductionmentioning

confidence: 99%

Formation of the acenaphthylene cation as a common C₂H₂-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene

Banhatti

Rap

Simon

et al. 2022

Phys. Chem. Chem. Phys.

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Cover Feature: Direct Evidence of the Benzylium and Tropylium Cations as the Two Long‐Lived Isomers of C₇H₇⁺ (ChemPhysChem 23/2018)

Cited by 3 publications

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Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Formation of the acenaphthylene cation as a common C₂H₂-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene

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Cover Feature: Direct Evidence of the Benzylium and Tropylium Cations as the Two Long‐Lived Isomers of C7H7+ (ChemPhysChem 23/2018)

Cited by 3 publications

References 0 publications

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Infrared action spectroscopy of doubly charged PAHs and their contribution to the aromatic infrared bands

Formation of the acenaphthylene cation as a common C2H2-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene

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Cover Feature: Direct Evidence of the Benzylium and Tropylium Cations as the Two Long‐Lived Isomers of C₇H₇⁺ (ChemPhysChem 23/2018)

Formation of the acenaphthylene cation as a common C₂H₂-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene