Fluorescence spectroscopy of jet-cooled o-fluoroanisole: mixing through Duschinsky effect and Fermi resonance.

Laser-induced fluorescence (LIF) excitation, UV-UV hole burning, and single vibronic level fluorescence (SVLF) spectra of jet-cooled o-fluoroanisole (o-FA) were measured. The most intense lowest-frequency band at 36 612 cm(-1) was assigned to the origin band of the most stable trans conformer. The UV-UV hole-burning spectrum demonstrated that the prominent bands in the LIF excitation spectrum were responsible for the trans conformer. The metastable non-planar conformer was not observed in the spectra. The vibrational band assignments were performed with the aid of quantum chemical calculations at the B3LYP/cc-pVTZ and CIS/6-311G(d,p) levels. The precise analysis of the SVLF spectra indicated that strong vibrational mixing through the Duschinsky effect and the Fermi resonance occurs in the S(1) state.