Revisit on the assignment of electronic spectra of C11H9+isomers

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.