Modelling vibronic spectra and the dynamics of non-radiative processes: From fully quantum to mixed quantum-classical approaches for nuclei
Speaker: Fabrizio Santoro, ICCOM-CNR, Pisa, Italy.
Quantum vibronic effects have a remarkable impact on the lineshape of electronic spectra.1They can also play an important role in the dynamics of photophysical processes, like internal conversions at Conical Intersections, or charge and energy transfer in multichromophoric systems. Recent advancements have made available rather standard approaches for a fair description of such effects in rigid (harmonic) molecules in gas phase.1-5 However, in biology and in material science the photoexcited chomophores are usually embedded in a solvent, possibly establishing with them specific interactions, or even in more complex and heterogeneous environments. Moreover, many systems with interesting optical properties are flexible, i.e. the optical transition triggers large-amplitude curvilinear distortions, and this challenges the applicability of harmonic approximation. Trajectory-based approaches are very suitable to deal with these scenarios but they neglect quantum nuclear effects. We are currently working to devise robust mixed quantum/classical (MQC) approaches to merge the potentialities of trajectory-based and quantum vibronic methods. The nuclear motions are partitioned in two subsystems: a quantum core (some or all the modes of the chromophores) and an environment (which can include also large amplitude motions of the system itself) that is treated at a more approximate classical level. The challenge is the reliable description of their mutual couplings. In this seminar I will give a brief overview of our contributions to the field of time-independent1 and time-dependent vibronic methods5and then I will illustrate our recent results with MQC approaches.6-8 A number of examples will be considered, ranging from the chiro-optical properties of flexible conjugated systems7,9 to the nonadiabatic spectra and photoexcited decay of photoexcited DNA nucleobases in gas10 and in aqueous solution.8
1. F. Santoro, R. Improta, A. Lami, J. Bloino, V. Barone, J. Chem. Phys. 126, 084509, 2007
2. F. Santoro, D. Jacquemin, WIREs Comput Mol Sci 6, 460486, 2016
3. M. H Beck,. A Jäckle,. G. A Worth, H.-D Meyer,. Physics Report 2000, 324
4. L. S. Cederbaum, E. Gindensperger, and I. Burghardt, Phys. Rev. Lett. 94, 113003, 2005.
5. F. Avila, J. Cerezo, J. Soto, R. Improta, F. Santoro, Comp. Chem. Theor. 1040-1041, 328, 2014
6. J. Cerezo, F. Avila, G. Prampolini, F. Santoro, J. Chem. Theor. Comp. 11, 5810, 2015
7. J. Cerezo, G. Mazzeo, G. Longhi, S. Abbate, F. Santoro J. Phys. Chem. Lett. 7, 4891, 2016
8. J. Cerezo, Y. Liu, N. Lin, X. Zhao, R. Improta, F. Santoro J. Chem. Theor. Comp. 14, 820, 2018
9. D. Padula, F. Santoro, G. Pescitelli RSC Adv. 6, 37928, 116, 3540, 2016
10. Y. Liu, J. Cerezo, L. Martinez, G. Prampolini, R. Improta, F. Santoro, submitted to Chem. Phys.