title: New Insights into the State Trapping of UV-Excited Thymine.
abstract: After UV excitation, gas phase thymine returns to a ground state in 5 to 7 ps, showing multiple time constants. There is no consensus on the assignment of these processes, with a dispute between models claiming that thymine is trapped either in the first (S₁) or in the second (S₂) excited states. In the present study, a nonadiabatic dynamics simulation of thymine is performed on the basis of ADC(2) surfaces, to understand the role of dynamic electron correlation on the deactivation pathways. The results show that trapping in S₂ is strongly reduced in comparison to previous simulations considering only non-dynamic electron correlation on CASSCF surfaces. The reason for the difference is traced back to the energetic cost for formation of a CO π bond in S₂.
authors.affiliation: Aix Marseille Univ., CNRS, ICR, Marseille, France. ljiljana.stojanovic@univ-amu.fr.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Stojanović
authors.affiliation: Aix Marseille Univ., CNRS, ICR, Marseille, France. shuming.bai@univ-amu.fr.
authors.forename: Shuming
authors.initials: S
authors.lastname: Bai
authors.affiliation: Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada. jnagesh@chem.utoronto.ca.
authors.forename: Jayashree
authors.initials: J
authors.lastname: Nagesh
authors.affiliation: Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada. artur.izmaylov@utoronto.ca.|Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada. artur.izmaylov@utoronto.ca.
authors.forename: Artur F
authors.initials: AF
authors.lastname: Izmaylov
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK. r.crespo-otero@qmul.ac.uk.
authors.forename: Rachel
authors.initials: R
authors.lastname: Crespo-Otero
authors.affiliation: School of Pharmaceutical Sciences and Technology, Tianjin University, Tianjin 300072, China. hans.lischka@univie.ac.at.|Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA. hans.lischka@univie.ac.at.
authors.forename: Hans
authors.initials: H
authors.lastname: Lischka
authors.affiliation: Aix Marseille Univ., CNRS, ICR, Marseille, France. mario.barbatti@univ-amu.fr.
authors.forename: Mario
authors.initials: M
authors.lastname: Barbatti
mesh_terms: D008956:Models, Chemical; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010777:Photochemistry; D013941:Thymine / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D013941:Thymine
keywords: computational theoretical chemistry; nonadiabatic dynamics; nucleobases; photochemistry; surface hopping; thymine; ultrafast processes