Electronic absorption spectra of hydrogenated protonated naphthalene and proflavine

Abstract

We study hydrogenated cations of two polycyclic hydrocarbon molecules as models of hydrogenated organic species that form in the interstellar medium. Optical spectra of the hydrogenated naphthalene cation Hn–C10H+8 for n= 1, 2 and 10, as well as the astrobiologically interesting hydrogenated proflavine cation Hn–C13H11N+3 for n= 1 and 14, are calculated. The pseudopotential time‐dependent density functional theory is used. It is found that the fully hydrogenated proflavine cation H14–C13H11N+3 shows a broad spectrum in which the positions of individual lines are almost lost. The positions, shapes and intensities of lines change in hydronaphthalene and hydroproflavine cations, showing that hydrogen additions induce substantially different optical spectra in comparison with base polycyclic hydrocarbon cations. One calculated line in the visible spectrum of H10–C10H+8 and one in the visible spectrum of H–C13H11N+3 are close to the measured diffuse interstellar bands. We also present the positions of near‐ultraviolet lines.

Formation and stability of hydrogenated PAHs in the gas phase

“…Both computational and experimental results show that protonation and hydrogen addition strongly influence the optical spectra (Pathak & Sarre 2008;Chakraborty et al 2009;Hammonds et al 2009;Ricks et al 2009;Knorke et al 2009;Garkusha et al 2011;Alata et al 2010;Bonaca & Bilalbegovic 2011). This indicates that, although bare and singly protonated PAHs can be ruled out as carriers of the DIBs (Steglich et al 2011), hydrogenated PAHs cannot.…”

Hydrogen-atom attack on phenol and toluene is ortho-directed

“…[10][11][12][13] Additionally, several reports characterizing the hydronaphthyl radical (H + naphthalene) have been reported recently. [14][15][16][17][18] However, the spectroscopy, structure, energetics and kinetics of H-addition to other common aromatics, such as toluene and phenol, are largely unreported.…”

H and D Attachment to Naphthalene: Spectra and Thermochemistry of Cold Gas-Phase 1-C10H9 and 1-C10H8D Radicals and Cations

“…The radical resulting from association of Np with an H atom, the dihydronaphthyl radical (NpH) has been studied in detail by the group of Zwier. , They obtained an ionization energy for the radical, linking it with the protonated species, NpH + . The cation, which is of specific astrophysical interest, has been studied spectroscopically, − by the group of Jouvet, who photodissociated NpH + formed by an electrical discharge, , and by us . In our study, we performed a triple-resonance experiment, where cold cations were prepared by resonant ionization of NpH at threshold, followed by photodissociation …”