Li, Yazhen
Gong, Qianqian
Yue, Ling
Wang, Wenliang
Liu, Fengyi
Photochemistry of the Simplest Criegee Intermediate,
CH<sub>2</sub>OO: Photoisomerization Channel toward Dioxirane Revealed
by CASPT2 Calculations and Trajectory Surface-Hopping Dynamics
The
photochemistry of Criegee intermediates plays a significant
role in atmospheric chemistry, but it is relatively less explored
compared with their thermal reactions. Using multireference CASPT2
electronic structure calculations and CASSCF trajectory surface-hopping
molecular dynamics, we have revealed a dark-state-involved <i>A</i><sup>1</sup>A → <i>X</i><sup>1</sup>A
photoisomerization channel of the simple Criegee intermediate (CH<sub>2</sub>OO) that leads to a cyclic dioxirane. The excited molecules
on the <i>A</i><sup>1</sup>A state, which can have either
originated from the <i>B</i><sup>1</sup>A state via <i>B</i><sup>1</sup>A → <i>A</i><sup>1</sup>A
internal conversion or formed by state-selective electronic excitation,
is driven by the out-of-plane motion toward a perpendicular <i>A</i>/<i>X</i><sup>1</sup>A minimal-energy crossing
point (MECI) then radiationless decay to the ground state with an
average time constant of ∼138 fs, finally forming dioxirane
at ∼254 fs. The dynamics starting from the <i>A</i><sup>1</sup>A state show that the quantum yield of photoisomerization
from the simple Criegee intermediate to dioxirane is 38%. The finding
of the <i>A</i><sup>1</sup>A → <i>X</i><sup>1</sup>A photoisomerization channel is expected to broaden the
reactivity profile and deepen the understanding of the photochemistry
of Criegee intermediates.
Simplest Criegee Intermediate;B 1;dynamic;CASSCF trajectory surface-hopping;CH 2 OO;multireference CASPT 2;photochemistry;Criegee intermediates;MECI;CASPT 2 Calculations;dioxirane;Trajectory Surface-Hopping Dynamics;photoisomerization channel
2018-02-08
https://acs.figshare.com/articles/journal_contribution/Photochemistry_of_the_Simplest_Criegee_Intermediate_CH_sub_2_sub_OO_Photoisomerization_Channel_toward_Dioxirane_Revealed_by_CASPT2_Calculations_and_Trajectory_Surface-Hopping_Dynamics/5877381

10.1021/acs.jpclett.8b00023.s001