Mass analyzed threshold ionization spectra of phenol•••Ar2: ionization energy and cation intermolecular vibrational frequencies

The phenol(+)center dot center dot center dot Ar-2 complex has been characterized in a supersonic jet by mass analyzed threshold ionization (MATI) spectroscopy via different intermediate intermolecular vibrational states of the first electronically excited state (S-1). From the spectra recorded via the S(1)0(0) origin and the S-1 beta(x) intermolecular vibrational state, the ionization energy (IE) has been determined as 68 288 +/- 5 cm(-1), displaying a red shift of 340 cm(-1) from the IE of the phenol(+) monomer. Well-resolved, nearly harmonic vibrational progressions with a fundamental frequency of 10 cm(-1) have been observed in the ion ground state (D-0) and assigned to the symmetric van der Waals (vdW) bending mode, beta(x), along the x axis containing the C-O bond. MATI spectra recorded via the S-1 state involving other higher-lying intermolecular vibrational states (sigma(1)(s), beta(3)(x), sigma(1)(s)beta(1)(x), sigma(1)(s)beta(2)(x)) are characterized by unresolved broad structures.