Autoionization-detected infrared spectroscopy of jet-cooled aromatic cations in the gas phase: CH stretching vibrations of isolated p-ethylphenol cations

The first observation of CH stretching vibrations of isolated aromatic molecular cations in the gas phase was performed by using autoionization-detected infrared (ADIR) spectroscopy. Aromatic and alkyl CH stretching vibrations of p-ethylphenol (p-EP) in the cationic ground state were observed and compared with those of the neutral ground state. Distinct high-frequency shifts of these vibrations upon ionization were found. CH stretching vibrations of the p-EP–Ar cluster cation were also measured by infrared photodissociation (IRPD) spectroscopy, providing essentially the same vibrational spectrum as that of the bare cation.