Excited State Dynamics of Cold Protonated Cytosine Tautomers: Characterization of Charge Transfer, Intersystem Crossing, and Internal Conversion Processes

Michel Broquier (1, 2) , Satchin Soorkia (1) , Gustavo Ariel Pino (3) , Claude Dedonder-Lardeux (4) , Christophe Jouvet (4) , Gilles Grégoire (1, 5)

1 ISMO - Institut des Sciences Moléculaires d'Orsay
2 CLUPS - Centre Laser de l'Université Paris Sud
3 INFIQC - Instituto de Investigaciones en Físico Química [Córdoba]
4 PIIM - Physique des interactions ioniques et moléculaires
5 SYSIPHE

Charge transfer reactions are ubiquitous in chemical reactivity and often viewed as ultrafast processes. For DNA, femtochemistry has undeniably revealed the primary stage of the deactivation dynamics of the locally excited state following electronic excitation. We here demonstrate that the full time scale excited state dynamics can be followed up to milliseconds through an original pump-probe photodissociation scheme applied to cryogenic ion spectroscopy. Protonat-ed cytosine is chosen as a benchmark system in which the locally excited 1 * state decays in the femtosecond range towards long-lived charge transfer and triplet states with lifetimes ranging from microseconds to milliseconds, respectively. A three-step mechanism (1 * → 1 CT → 3 *) is proposed where internal conversion from each state can occur leading ultimately to fragmentation in the ground electronic state.

Domaines: Chimie-Physique [physics.chem-ph]; Agrégats Moléculaires et Atomiques [physics.atm-clus]

Michel Broquier, Satchin Soorkia, Gustavo Ariel Pino, Claude Dedonder-Lardeux, Christophe Jouvet, et al.. Excited State Dynamics of Cold Protonated Cytosine Tautomers: Characterization of Charge Transfer, Intersystem Crossing, and Internal Conversion Processes. Journal of Physical Chemistry A, 2017, 121 (34), pp.6429-6439. ⟨10.1021/acs.jpca.7b06423⟩. ⟨hal-02464341⟩