Mass-analyzed threshold ionization spectroscopy of trans-o-methylanisole

In this study, we recorded the vibronic and cation spectra of trans-o-methylanisole by using resonant two-photon ionization and mass-analyzed threshold ionization techniques. The excitation energy of the S-1 <- S-0 transition and the adiabatic ionization energy were measured as 36,364 +/- 2 cm(-1) and 64,755 +/- 5 cm(-1), respectively. The red shifts of these values with respect to those of anisole and toluene indicated that the interactions of CH3 and OCH3 substituents with the ring are stronger in the electronically excited S-1 and cationic ground Do states than that in the electronically ground S o state. Most of the observed bands in the S-1 and D-0 states involve in-plane ring deformation and methyl internal rotation. The vibrational frequencies of modes 6b(1), 6a(l), and 1(1) were lower in the S-1 state than in the D-0 state. This suggested that trans-o-methylanisole is more rigid in the D-0 state than in the S-1 state. (C) 2018 Elsevier Inc. All rights reserved.