Molecular Structure, Vibrational Spectrum and Ionization Energy of m-Dimethoxybenzene

The optimized molecular geometries of the three rotamers of m-dimethoxybenzene in the ground S₀ and electronically excited S₁ states were predicted by ab initio and density functional theory (DFT) calculations. Their vibrational spectra in the S₁ state were studied by one color resonant two photon ionization (1C-R2PI) method, and their ionization energies were measured by two color resonant two photon ionization (2C-R2PI) experiment. The optimized molecular geometries showed that the total energy of conformer a was the lowest in the S₀ state. Most of the active vibrations assigned from the 1C-R2PI spectrum were found to be of the in-plane ring modes. The ioniza- tion energies (IE) of conformers a, b and c were determined to be 63521, 64487 and 63755 cm⁻¹, respectively.