Vibronic and cation spectroscopy of 2,4-difluoroaniline

We applied the two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 2,4-difluoroaniline. The cation spectra were recorded by ionizing via the 00, X1, 6b1, and 11 levels of the electronically excited S1 state. Most of the observed active modes of this molecule in the S1 and cationic ground D0 states are related to the in-plane ring deformation vibrations. The band origin of the S1 ← S0 electronic excitation was found to appear at 33 294 ± 2 cm−1, whereas the adiabatic ionization energy was determined to be 63 935 ± 5 cm−1. Comparing the data of 2,4-difluoroaniline with those of aniline, 2-fluoroaniline, and 4-fluoroaniline, one can learn the effects of fluorine substitution on the electronic transition and molecular vibration.

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► The vibronic and cation spectra of 2,4-difluoroaniline have been recorded.
► The electronic excitation and ionization energies are precisely determined.
► The observed vibrations involve in-plane ring motions and amino inversion.