Issue 29, 2023

Photodissociation dynamics and UV absorption spectrum of acetone oxide (CH3)2COO

Abstract

The photodynamics and B1A′ ← X1A′ absorption spectrum of acetone oxide, (CH3)2COO, are studied theoretically from first principles. The underlying adiabatic potential energy curves (and surfaces) are computed by a second-order multireference perturbation theory method and diabatized using a diabatization by ansatz scheme. To confirm the results, for selected geometries EOM-CCSD and XMS-RS2C calculations were also performed. The dynamical calculation rests on the multi-configuration time-dependent Hartree wavepacket propagation method. The experimental absorption spectrum is reproduced satisfactorily. This result serves to validate the Hamiltonian model built within the quasi-diabatic representation. Contrary to the smallest Criegee intermediate, CH2OO, it is found that the vibronic coupling between the B and C states of (CH3)2COO plays an essential role in reproducing the experimental absorption spectrum. Time-dependent electronic populations reveal a faster decay than for the smaller system CH2OO. This is interpreted in terms of the stronger coupling between the B and C states in the larger system leading to a shorter lifetime for the B state than in CH2OO.

Graphical abstract: Photodissociation dynamics and UV absorption spectrum of acetone oxide (CH3)2COO

Article information

Article type
Paper
Submitted
17 Mot 2023
Accepted
26 Jan 2023
First published
13 Upu 2023

Phys. Chem. Chem. Phys., 2023,25, 19470-19480

Photodissociation dynamics and UV absorption spectrum of acetone oxide (CH3)2COO

B. Nikoobakht and H. Köppel, Phys. Chem. Chem. Phys., 2023, 25, 19470 DOI: 10.1039/D3CP02246C

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