Resonance-enhanced two-photon ionization spectroscopy and theoretical calculations of 3,5-difluoroanisole and its Ar-containing complex

The structure and vibrations of 3,5-difluoroanisole (3,5-DFA) in the first electronically excited (S-1) state were studied by mass-analyzed resonant two-photon ionization (R2PI) technique as well as the quantum chemical calculations. The ab initio and density functional theory (DFT) calculations reveal that only one structure is stable for each of the S-0, S-1, and D-0 states. In the one color R2PI spectrum, the band origin of the S-1 <- S-0 electronic transition (0 degrees band) of 3,5-DFA is found to be 37,595 +/- 3 cm(-1). In the S-1 state, most of the bands observed are related to the in-plane ring deformation and out-of-plane bending vibrations. The adiabatic ionization energy (IE) of 3,5-DFA is determined to be 70,096 +/- 15 cm(-1) by the two color R2PI technique, in agreement with the values predicted by the DFT approaches. The dihalogen-substitution effects on the molecular structure, vibrational frequencies, and electronic transition and ionization energies were discussed in detail. The van der Waals complex of 3,5-DFA with argon (3,5-DFA center dot center dot center dot Ar) was also observed and studied. The 0 degrees band of 3,5-DFA center dot center dot center dot Ar complex is red-shifted by about 9 cm(-1) with respect to that of 3,5-DFA. Both the experimental data and the calculated results indicate that the formation of 3,5-DFA center dot center dot center dot Ar complex gives only a weak influence on the properties of 3,5-DFA moiety. (c) 2012 Elsevier B.V. All rights reserved.