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 mole cular cations in the gas phase was performed by using autoionization-detect ed infrared (ADIR) spectroscopy. Aromatic and alkyl CH stretching vibration s of p-ethylphenol (p-EP) in the cationic ground state were observed and co mpared with those of the neutral ground state. Distinct high-frequency shif ts of these vibrations upon ionization were found. CH stretching vibrations of the p-EP-Ar cluster cation were also measured by infrared photodissocia tion (IRPD) spectroscopy, providing essentially the same vibrational spectr um as that of the bare cation. (C) 1999 Elsevier Science B.V. All rights re served.