A computational method for vibrational resonance Raman, including Duschinsky, Herzberg-Teller and multiple electronic resonances effects

A computational method for vibrational resonance Raman, including Duschinsky, Herzberg-Teller and multiple electronic resonances effects. Fabrizio Santoro1, Francisco Avila1,2 1 CNR--Istituto di Chimica dei Composti Organometallici, Area della Ricerca di Pisa, via Moruzzi 1 56124 Pisa (fabrizio.santoro@iccom.cnr.it) 2 Physical Chemistry, Faculty of Science, University of Ma?laga, Ma?laga 29071, Spain We recently presented an effective time-independent (TI) method for the computation of vibrational resonance Raman (vRR) spectra including Duschinsky rotation and Herzberg-Teller effects [1]. It is based on a sum-over-state approach and a prescreening technique able to individuate only the relevant terms of the sum in order to get converged results [2]. The fundamental quantity computed by the method is the transition polarizability tensor for fundamental, overtone and binary combination bands, and it is obtained as a function of the excitation frequency and the Raman shift (2D spectrum), taking into account the effect of all the vibrational modes of the molecule. This allows us to investigate both the vRR spectra and the associated Raman excitation profiles and to account for the effects of multiple electronic resonances, by simply summing the polarizability tensors for each quasi-resonant state. For semi-rigid molecules, where harmonic approximation provides a reasonable description of the ground and excited state potential energy surfaces (PES), the method is effective enough to deliver converged spectra for systems with dozens of normal modes and it has been applied to phenoxyl radical [1], indolinedimethine-malononitrile (IDMN, [1]), trans-stilbene [3] and pyrene [4]. In this contribution, we present the method and some of its most recent applications, analyzing also the impact on the simulated spectra of different approximations to build the resonant-state PES (vertical and adiabatic models [5]) References [1]F. Santoro, C. Cappelli, V. Barone J. Chem. Theor. Comp. 7, 1824 (2011). [2]F. Santoro, A. Lami, R. Improta, J. Bloino, V. Barone J. Chem Phys. 128, 224311 (2008). [3] N. Lin, V. Barone, C. Cappelli, X. Zhao, K. Ruud, F. Santoro, Mol. Phys . 111, 1511 (2013) [4] F. Avila, V. Barone, C. Cappelli, F. Santoro, J. Chem. Theor. Comp 9, 3597 (2013) [5] F. Avila, F. Santoro, Phys. Chem. Chem. Phys. 14, 13549 (2012)