Electronic absorption spectra of phenol dimer and toluene—cyanobenzene complex as studied by mass-selected MPI—nozzle beam method

S₀–S₀ absorption spectra of phenol dimer and toluene-cyanobenzene complex in a supersonic free jet have been observed by the use of the multiphoton ionization technique. Two low-frequency vibrations at 15 and 112 cm^-1 appear in the spectrum of phenol dimer, which were assigned as the bending and stretching mode of hydrogen bonding, respectively. Toluene—cyanobenzene complex also exhibits a low-frequency vibrational progression which indicates the dissociation of the complex in the S₁ state.