Observation of rotational isomers I: A ZEKE and hole-burning spectroscopy study of 3-methoxyphenol

Three rotational isomers of 3-methoxyphenol have been studied using two-col or resonance-enhanced multiphoton ionization (REMPI) and zero kinetic energ y (ZEKE) photoelectron spectroscopy. Hole-burning spectroscopy was employed to confirm the presence of three isomers in the REMPI spectrum (S-1 band o rigins were identified at 35 974, 36 034 and 36 202 +/- 1 cm(-1) for isomer s I, IV, and III, respectively). ZEKE spectra recorded via the SI states of the isomers provide adiabatic ionization energies of 65 228, 64 741, and 6 5 648 +/- 5 cm(-1), respectively. The isomers are assigned with the aid of HF/cc-pVDZ, MP2/cc-pVDZ, and B3LYP/cc-pVDZ ab initio and density functional theory calculations. We discuss the characteristics of the 3-methoxyphenol rotational isomers by comparing the REMPI and ZEKE spectra with those of o ther substituted benzenes.