Article pubs.acs.org/JPCA
H and D Attachment to Naphthalene: Spectra and Thermochemistry of Cold Gas-Phase 1‑C10H9 and 1‑C10H8D Radicals and Cations Olha Krechkivska,† Callan M. Wilcox,† Bun Chan,‡ Rebecca Jacob,‡ Yu Liu,† Klaas Nauta,† Scott H. Kable,† Leo Radom,‡ and Timothy W. Schmidt*,† †
School of Chemistry, The University of New South Wales, Sydney, New South Wales 2052, Australia School of Chemistry and Centre of Excellence for Free Radical Chemistry and Biotechnology, The University of Sydney, Sydney, New South Wales 2006, Australia
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S Supporting Information *
ABSTRACT: Excitation spectra of the 1H-naphthalene (1-C10H9) and 1D-naphthalene (1-C10H8D) radicals, and their cations, are obtained by laser spectroscopy and mass spectrometry of a skimmed free-jet expansion following an electrical discharge. The spectra are assigned on the basis of density functional theory calculations. Isotopic shifts in origin transitions, vibrational frequencies and ionization energies were found to be well reproduced by (time-dependent) density functional theory. Absolute bond dissociation energies, ionization energies and proton affinities were calculated using high-level quantum chemical methods.
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INTRODUCTION The interaction of hydrogen atoms with graphene surfaces is of relevance to both the pure and applied ends of the scientific spectrum. It is crucial to the understanding of molecular hydrogen formation in the interstellar medium (ISM),1 and is also a promising candidate for hydrogen storage.2 Molecular hydrogen is necessary for star formation, and for the further production of complex molecules which make up the interstellar medium. However, there is no efficient gasphase route for H2 formation. Due to energy and angular momentum constraints, and due to the low gas densities in the ISM, H2 cannot be produced by two- or three-body collisions. It is widely accepted that H2 formation takes place on the surfaces of interstellar grains, which are held to be silicaceous or carbonaceous in nature, bare in diffuse clouds but with accreted ice mantles in dark clouds. The interaction of H atoms with graphitic carbon is thus of fundamental importance. There have been many studies on the interactions of H atoms with graphene surfaces.3,4 When confronted with a quasiinfinite graphene sheet, a hydrogen atom attaches atop a carbon atom, rehybridizing it from sp2 to sp3. The carbon puckers out of plane by 0.35 Å, and the hydrogen is bound by about 0.67 eV. H2 formation subsequently takes place by the Eley−Rideal mechanism.1−3,5 It is likely that defects and other deviations from the ideality of an infinite graphene sheet are also important, including edge effects. A graphene sheet with hydrogenated edges may also be considered a large polycyclic aromatic hydrocarbon. Rauls and Hornekær studied H adsorption to coronene, showing that © 2015 American Chemical Society
chemisorption at the edge was preferred, with a lower barrier and a stronger resulting bond (>1.4 eV).6 Adsorption at the edge was also shown to proceed with a much lower barrier
