| We have performed rotationally resolved fluorescence excitation spectroscopy experiments on large polyatomic molecules and their molecular complexes formed in a supersonic jet expansion, both in the absence and presence of a static electric field. The information obtained from such experiments includes a measure of the moments of inertia, from which we derive structural information about both electronic states; the S1-S0 electronic transition moment, which we use to obtain information about the electronic structure of such systems, and how that structure is modified by complexation with a single solvent molecule, or conformational change; and, when the electric field is applied, the electric dipole moment and how it changes upon absorption of a photon. We have used this information to show, among other things, that the electronic structure of n-propylbenzene is modified by a conformational change, that similar changes occur in benzonitrile upon complexation with a single water molecule, and that toluene undergoes structural modification during the course of methyl torsion. Further, we have shown that the dipole moments of aniline, benzonitrile and p-aminobenzonitrile can be measured in both electronic states. All of this information is relevant to the development of models for chemical reactivity, both in the presence and absence of light. |
