title: Resonance Raman de-enhancement caused by excited state mixed valence.
abstract: Resonance Raman and absorption spectra of 9,10-bis(2-tert-butyl-2,3-diazabicyclo[2.2.2]oct-3-yl)-anthracene (2) are measured and analyzed. The contribution of the individual vibrational normal modes to the reorganization energy is investigated. Excited-state mixed valence in this system is analyzed using density functional theory electronic structure calculations. The resonance Raman excitation profiles exhibit a resonance de-enhancement effect around 20 725 cm-1, but a corresponding feature is not observed in the absorption spectrum. This unusual observation is attributed to the presence of a dipole-forbidden, vibronically allowed component of the split mixed valence excited state. The de-enhancement dip is calculated quantitatively and explained in terms of the real and imaginary components of the polarizabilities of the two overlapping excited states.
authors.affiliation: Department of Chemistry and Biochemistry, University of California-Los Angeles, CA 90095, USA.
authors.forename: Xianghuai
authors.initials: X
authors.lastname: Wang
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Valverde-Aguilar
authors.forename: Michael N
authors.initials: MN
authors.lastname: Weaver
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Nelsen
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Zink