Revisit on the assignment of electronic spectra of C11H9+ isomers

Abstract

The polycyclic aromatic hydrocarbon cation C11H9+ is the reaction intermediate for the growth process of large PAHs in the interstellar space and combustion process. The assignment for the absorption and emission spectra of C11H9+ isomers has been revisited based on the vibronic structure analysis. By carefully comparing the 0–0 transition energy and their spectral profiles with the experimental spectra, we can draw the following conclusions: the previous identification of the experimental spectra of C11H9+ isomers is inadequate. We found that the absorption and emission spectra near 560 nm can be classified as isomer 1-NyMe+ but not 2-NyMe+ while the absorption and emission bands near 460 nm in the experimental spectra should be contributed to the isomer BzTr+. It is shown again that the calculated vertical excitation energy often leads to incorrect spectral identification for the isomers of PAHs cations.