Hydrogen dissociation of naphthalene cations: a theoretical study

Jolibois, Franck; Klotz, A.; Gadéa, Florent Xavier; Joblin, C.

doi:10.1051/0004-6361:20053508

Cited by 40 publications

(40 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22,23 For the neutral molecule, comparable values are obtained with only a different ordering between the two fragments. 34,35,44 The energy difference is predicted to be 0.07 eV between the two channels.…”

Section: Dft Calculationsmentioning

confidence: 71%

Theoretical Rates for the Emission of Atomic Hydrogen from a Naphthalene Cation

et al. 2007

View full text Add to dashboard Cite

The statistical phase space theory (PST) in its orbital transition state version has been used to calculate the dissociation rate associated with the loss of atomic hydrogen from a polycyclic aromatic hydrocarbon molecule. The PST model has been applied to the naphthalene cation with input data obtained exclusively from first-principle calculations using density functional theory. Without any fitting parameters, the calculated dissociation rates are found to agree well with available measurements. The effects of vibrational anharmonicities are investigated and are shown to lower the dissociation rates by a factor of about five.

show abstract

Section: Dft Calculationsmentioning

confidence: 71%

Theoretical Rates for the Emission of Atomic Hydrogen from a Naphthalene Cation

et al. 2007

View full text Add to dashboard Cite

show abstract

“…It is also possible that the cations could lose a hydrogen atom to improve the C-C bonding. The loss of an H atom for a PAH cation was found (Jolibois et al 2005) to be favored over the loss of H 2 , and we suspect this will also be true for the diamondoids.…”

Section: Diamondoid Cation Vibrational Spectroscopymentioning

confidence: 87%

Electronic and Vibrational Spectroscopy of Diamondoids and the Interstellar Infrared Bands between 3.35 and 3.55 μm

Bauschlicher

Liu

Ricca

et al. 2007

ApJ

View full text Add to dashboard Cite

The electronic and vibrational spectroscopic properties and ionization energies of diamondoids (nano-diamonds, microdiamonds) are computed using density functional theory (DFT). Spectra of both the neutral and cationic forms of diamondoids, ranging in size from C 10 H 16 to C 38 H 42 , and the IR spectrum of a diamondoid-PAH hybrid molecule are presented. For the 23 neutral species, the C-H stretching bands fall near 3.47 m and are the strongest in the spectra. Diamondoid ionization energies (IEs) are found to be quite large (about 8 eV ). The electronic excitation energies of the neutral species are of the same order as the IEs and have very small oscillator strengths ( f-values). For the cations, the C-H stretching peak positions differ somewhat from the neutrals and their average integrated band strengths are about half those of the neutrals. The computed electronic excitation energies for the cations are much smaller than those of the neutral species, with f-values that are very small. The neutral diamondoids will absorb most strongly near 3.47 m, which is very close to the position of an absorption band associated with dense clouds that has been tentatively attributed to the tertiary C-H stretch of diamond-like carbon. The spectroscopic properties described here imply that 3 m emission from highly vibrationally excited diamondoid cations and neutral species should be most intense in regions with strong radiation fields. These results, in conjunction with the observation that the 3.5 m emission feature originates very close to the exciting star, strongly supports its assignment in HD 97048 and Elias 1 to diamondoid species. While previous work makes an excellent case for large neutral diamondoids, our work shows that some cation contribution cannot be excluded. The very small f-values explain why so few sources show this emission.

show abstract

“…This 1,2-hydrogen (or deuterium) shift is a well-known phenomenon in organic chemistry (Whitmore 1932;Kuck 2002;Bruice 2014), and specifically for reactions in aromatic molecules (Brooks & Scott 1999). Furthermore, in theoretical studies of PAH species, the 1,2-H shift across the PAH rim has been shown to occur once they are excited to internal energies above 1 eV, leading to the formation of various intermediate isomers containing a C -HH group (Jolibois et al 2005;Trinquier et al 2017;Castellanos et al 2018b). Using DFT, we calculated the potential energy reaction pathway for D migration along [H -C 14 D 10 ] + , and the results are depicted in Fig.…”

Section: Discussionmentioning

confidence: 99%

Photolysis-induced scrambling of PAHs as a mechanism for deuterium storage

Wiersma

Candian

Bakker

et al. 2020

A&A

View full text Add to dashboard Cite

Aims We investigate the possible role of polycyclic aromatic hydrocarbons (PAHs) as a sink for deuterium in the interstellar medium (ISM) and study UV photolysis as a potential underlying chemical process in the variations of the deuterium fractionation in the ISM. Methods The UV photo-induced fragmentation of various isotopologs of deuterium-enriched, protonated anthracene and phenanthrene ions (both C 14 H 10 isomers) was recorded in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FTICR MS). Infrared multiple photon dissociation (IRMPD) spectroscopy using the Free-Electron Laser for Infrared eXperiments (FELIX) was applied to provide IR spectra. Infrared spectra calculated using density functional theory (DFT) were compared to the experimental data to identify the isomers present in the experiment. Transition-state energies and reaction rates were also calculated and related to the experimentally observed fragmentation product abundances. Results The photofragmentation mass spectra for both UV and IRMPD photolysis only show the loss of atomic hydrogen from [D -C 14 H 10 ] + , whereas [H -C 14 D 10 ] + shows a strong preference for the elimination of deuterium. Transition state calculations reveal facile 1,2-H and -D shift reactions, with associated energy barriers lower than the energy supplied by the photo-excitation process. Together with confirmation of the ground-state structures via the IR spectra, we determined that the photolytic processes of the two different PAHs are largely governed by scrambling where the H and the D atoms relocate between different peripheral C atoms. The ∼0.1 eV difference in zero-point energy between C -H and C -D bonds ultimately leads to faster H scrambling than D scrambling, and increased H atom loss compared to D atom loss. Conclusion We conclude that scrambling is common in PAH cations under UV radiation. Upon photoexcitation of deuterium-enriched PAHs, the scrambling results in a higher probability for the aliphatic D atom to migrate to a strongly bound aromatic site, protecting it from elimination. We speculate that this could lead to increased deuteration as a PAH moves towards more exposed interstellar environments. Also, large, compact PAHs with an aliphatic C -HD group on solo sites might be responsible for the majority of aliphatic C -D stretching bands seen in astronomical spectra. An accurate photochemical model of PAHs that considers deuterium scrambling is needed to study this further.

show abstract

Hydrogen dissociation of naphthalene cations: a theoretical study

Cited by 40 publications

References 26 publications

Theoretical Rates for the Emission of Atomic Hydrogen from a Naphthalene Cation

Theoretical Rates for the Emission of Atomic Hydrogen from a Naphthalene Cation

Electronic and Vibrational Spectroscopy of Diamondoids and the Interstellar Infrared Bands between 3.35 and 3.55 μm

Photolysis-induced scrambling of PAHs as a mechanism for deuterium storage

Contact Info

Product

Resources

About