Structure and vibrations of 2-fluoro-N-methylaniline in the S-0, S-1 and D-0 states: REMPI and MATI spectroscopy and theoretical calculations

Abstract Theoretical calculations predicted that there are only two stable conformers, trans and cis , for 2-fluoro-N-methylaniline (2FNMA) in the S 0 , S 1 and D 0 states. Compared to the cis conformer, the trans one is more stable, and has a population more than 99% at room temperature. The optimized molecular skeleton of trans and cis 2FNMA are both non-planar in the S 0 state, but planar in the S 1 and D 0 states. The one-dimensional potential energy surface of 2FNMA in the S 0 state is obtained. The Resonance-enhanced two-photon ionization (R2PI) and Mass-analyzed threshold ionization (MATI) spectra of trans 2FNMA are obtained. The first electronic excitation energy (E 1 ) and the adiabatic ionization energy (IE) of trans 2FNMA are determined. The substitution effect on the molecular structures, transition energies and vibrations of 2FNMA are discussed.