On the possible contribution of cationic oxygenated carbon chains CnO+, HCnO+, and OCnO+ (n = 4–9) to the diffuse interstellar bands. Issue 4 (31st January 2022)

• Record Type: Journal Article
• Authors: Jacovella, U; Buntine, Jack T; Cotter, Mariah; Muller, Giel; Scholz, Michael S; Dartois, Emmanuel
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 4(2022)
• Page Start: 5171
• Page End: 5179
• Publication Date: 2022-01-31
• Subjects: astrochemistry -- ISM: lines and bands -- ISM: molecules; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac277
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Only four of the diffuse interstellar bands (DIBs) are currently accounted for, ascribed to electronic transitions of C$_{60}^+$ . Investigations into carriers of other DIBs historically focus on charged and neutral hydrocarbons, and little information is available regarding oxygenated carbon and hydrocarbon species that result from the two most abundant heavy elements in the interstellar medium, C and O. In this study, we assess whether C n O +, HC n O +, and OC n O + ( n = 4–9) cations are viable candidates to account for DIBs using both density-functional theory (DFT) and coupled cluster single-double and perturbative triple theory, CCSD(T). For these species, the linear structures are the most stable isomers with the lowest dissociation threshold corresponding to CO loss. Optical absorptions of the oxygenated carbon chain cations are characterized by calculated vertical excitation wavelengths and their corresponding oscillator strengths using the equation-of-motion CCSD (EOM-CCSD) method. Aside from HC4 O + and HC2 n +1 O +, all of the species considered in this study have calculated electronic transitions that lie in the visible or near-infrared spectral regions. Minimal column densities necessary for these cations to account for DIBs have been estimated. Based on present results and the known column densities for neutral oxygenated carbon chains in TMC-1, the growth rate of charged O-bearing carbon chains via ion-neutral reaction mechanisms is judged to be too low to form a sufficient population to give rise to DIBs.