Knowledge Bank

Rotationally resolved fluorescence excitation spectra of the four origin bands that appear in the $S1-S0$ electronic transition of methyl -3-methoxybenzoate have been obtained and analyzed. The four origins have been assigned to conformers associated with cis and trans configurations of the $OCH3$ substituent and cis and trans configurations of the ester substituent, based on their inertial parameters. Further analysis makes possible llie determination of the absolute orientation of the transition moment in the molecular frame of each of the four conformers and its dependence upon both the inertial and electronic properties of the substituents.