title: Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene.
abstract: We show that a recently developed time-independent approach for the calculation of vibrational resonance Raman (vRR) spectra is able to describe Duschinsky and Herzberg-Teller (HT) effects acting on a single resonant state, together with interferential contributions arising from multiple electronic resonances, allowing us to investigate in detail how their interplay determines both the vRR spectra at selected wavelengths and the Raman excitation profiles. We apply this methodology to the study of the spectra of pyrene in acetonitrile, an ideal system since it exhibits three close-lying electronic transitions that are bright but also subjected to HT effects. To single out the different contributions to vRR line shapes we adopted two different adiabatic models for resonant-state potential energy surfaces, namely, Adiabatic Shift (only accounting from equilibrium geometry displacements) and Adiabatic Hessian (AH, including also the Duschinsky effects), and Franck-Condon (FC) or HT approximations for the transition dipole. We show that, on balance, FC+HT calculations within the AH model provide the best agreement with experiment. Moreover, our methodology permits to individuate bands in the experimental spectra due to the simultaneous contribution of more than one resonant state and to point out and analyze interferential effects between the FC and HT terms in each resonance Raman process, together with FC-HT and HT-HT interferences between different electronic states.
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa , Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy.|Physical Chemistry, Faculty of Science, University of Málaga , Málaga 29071, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Avila Ferrer
authors.affiliation: Scuola Normale Superiore di Pisa , Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Barone
authors.affiliation: Scuola Normale Superiore di Pisa , Piazza dei Cavalieri 7, I-56126 Pisa, Italy.|Dipartimento di Chimica e Chimica Industriale dell'Università di Pisa , Via Risorgimento 35, I-56126 Pisa, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cappelli
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa , Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Santoro