Title: Photofragmentation of cyclobutanone at 200 nm: TDDFT vs CASSCF electron diffraction

Authors: Alberto Martín Santa Daría, Javier Hernández-Rodríguez, Lea M. Ibele, and Sandra Gómez

DOI: https://doi.org/10.1063/5.0197895

Date: 03/15/2024

Working Group: WG2

Grant Period: 2nd GP 2023-2024

Grant Period Goal (number): GAPG-6/WG5, GAPG-8, GAPG-2

Countries involved: Spain, France

Number of female/young/ITC coauthors: 2/4/0

Abstract: To simulate a 200 nm photoexcitation in cyclobutanone to the n-3s Rydberg state, classical trajectories were excited from a Wigner distribution to the singlet state manifold based on excitation energies and oscillator strengths. Twelve singlet and 12 triplet states are treated using TD-B3LYP-D3/6-31+G** for the electronic structure, and the nuclei are propagated with the Tully surface hopping method. Using time-dependent density functional theory, we are able to predict the bond cleavage that takes place on the S1 surface as well as the ultrafast deactivation from the Rydberg n-3s state to the nπ*. After showing that triplet states and higher-lying singlet states do not play any crucial role during the early dynamics (i.e., the first 300 fs), the SA(6)-CASSCF(8,11)/aug-cc-pVDZ method is used as an electronic structure and the outcome of the non-adiabatic dynamic simulations is recomputed. Gas-phase ultrafast electron diffraction spectra are computed for both electronic structure methods, showing significantly different results.


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