Rotamers of 3,4-difluoroanisole studied by two-color resonant two-photon mass-analyzed threshold ionization spectroscopy

We reported the vibronic and cation spectra of 3,4-difluoroanisole. The band origins of the S1 ← S0 electronic transition of the cis and trans rotamers appear at 35,505 ± 2 and 35,711 ± 2 cm−1 and the adiabatic ionization energies are determined to be 67,780 ± 5 and 68,125 ± 5 cm−1, respectively. Most of the observed active vibrations in the electronically excited S1 and cationic ground D0 states mainly involve in-plane ring deformation and substituent-sensitive bending vibrations. Analysis of the obtained vibronic and cation spectra suggests that the molecular geometry, symmetry, and vibrational coordinates of the cation in the D0 state are like those of the neutral species in the S1 state for these two isomeric species.

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► The vibronic and cation spectra of 3,4-difluoroanisole have been recorded.
► Our experiments show the cis and trans rotamers of 3,4-difluoroanisole coexist.
► Most of the observed active vibrations involve in-plane motions.