Cavity ring-down spectroscopy of jet-cooled 1-pyrenecarboxyaldehyde (C17H10O) and 1-methylpyrene (C17H12) cations

To study the correlation between pyrene-like species and the diffuse interstellar bands (DIBs), we have investigated the electronic transitions of 1-pyrenecarboxaldehyde+ and 1-methylpyrene+, which were prepared with a pulsed discharge slit nozzle and detected by cavity ring-down spectroscopy. Several vibronic bands were observed near the λ4428 DIB is detected. Time-dependent density functional theory calculations were performed to aid the assignment of these bands. It is found that none of the observed bands correlate with the λ4428 DIB. The effect of side groups on the vibronic spectrum of pyrene+ is discussed.