REMPI and MATI spectroscopy of cis and trans 4-chloro-3-fluoroanisole

Abstract The Resonance-enhanced two-photon ionization (R2PI) and Mass-analyzed threshold ionization (MATI) spectra of 4-chloro-3-fluoroanisole (4Cl3FA) were recorded in detail. The experimental and calculated results revealed that cis and trans 4Cl3FA are the only two stable conformers in each of the S 0 , S 1 and D 0 states. The first electronic excitation energies (E 1 ’s) of cis and trans 35 Cl-4Cl3FA were measured to be 35,326 ± 3 and 35,443 ± 3 cm −1 by the R2PI spectroscopy and the corresponding adiabatic ionization energies (IEs) were determined to be 67,330 ± 5 and 67,591 ± 5 cm −1 by the MATI spectroscopy. The E 1 ’s and IEs of cis and trans 37 Cl-4Cl3FA were also obtained and found to be identical to that of the 35 Cl-4Cl3FA conformers. Compared with the trans 4Cl3FA, the cis 4Cl3FA is more stable in the S 0 , S 1 and D 0 states. The vibrational bands observed in the R2PI and MATI spectra are related to the vibrations involving the in-plane deformation of the benzene ring, the CH 3 torsion and the OCH 3 inversion. The substituent effects on the molecular structures, transition energies and vibrations of 4Cl3FA are discussed.