# Dynamical Insights into the Decomposition of 1,2-Dioxetane

## TL;DR

This study uses dynamic simulations to analyze the decomposition process of 1,2-dioxetane, revealing the roles of entropic traps and excited states in its chemiluminescent reaction pathway.

## Contribution

It provides detailed insights into the nonadiabatic and ground-state dynamics of 1,2-dioxetane decomposition, highlighting geometrical conditions and conical intersection regions affecting dissociation.

## Key findings

- Ground-state dissociation occurs between 30 fs and 140 fs.
- Entropic traps delay the decomposition process.
- Excited states extend the dissociation times up to 250 fs.

## Abstract

Chemiluminescence in 1,2-dioxetane occurs through a thermally activated decomposition reaction into two formaldehyde molecules. Both ground-state and nonadiabatic dynamics (including singlet excited states) of the decomposition reaction have been simulated, starting from the first O-O bond-breaking transition structure. The ground-state dissociation occurs between t = 30 fs and t = 140 fs. The so-called entropic trap leads to frustrated dissociations, postponing the decomposition reaction. Specific geometrical conditions are necessary for the trajectories to escape from the entropic trap and for dissociation to be possible. The singlet excited states participate as well in the trapping of the molecule: dissociation including the nonadiabatic transitions to singlet excited states now occurs from t = 30 fs to t = 250 fs and later. Specific regions of the seam of the S0/S1 conical intersections that would "retain" the molecule for longer on the excited state have been identified.