Photodynamics of Azomethane: A Nonadiabatic Surface-Hopping Study^†

Abstract

The internal conversion and hot ground-state dynamics of trans- and cis-azomethane starting in the S(1) state have been investigated by nonadiabatic ab initio surface hopping dynamics using MCSCF-GVB-CAS and MRCISD methods and by determining energy minima and saddle points, minima on the crossing seam, and minimum energy pathways on the ground and first excited-state surfaces. The lifetimes and photoproducts from the dynamics simulations, geometric properties, excitation energies of selected stationary points and minimum energy pathways between them are reported. Our results favor a statistical model with trans-AZM moving to the ground-state minima before the first CN dissociation takes place. A detailed discussion in comparison to recent experimental and theoretical data is presented.

Theoretical study of the excitation spectrum of azomethane

“…The most extensive one by Diau and Zewail [3] treated a large set of valence and Rydberg states at the TDDFT level. Calculations restricted to selected valence states have been reported by Morokuma and co workers [13] and Sellner et al [10]. All these studies have been restricted to vertical excitations using the fixed geometry of the ground state equilibrium.…”

“…1) is an interesting compound because of its role as a source for methyl radicals on irradiation with UV light [1]. The photodynamics of AZM after excitation into the first singlet excited state in the 350-300 nm range has been studied extensively both experimentally [2][3][4][5][6][7][8] and theoretically [9,10].…”

Ab Initio Based Surface-Hopping Dynamics Study on Ultrafast Internal Conversion in Cyclopropanone

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In the past decades, substantial progress in understanding the photodissociation dynamics of the smalland medium-sized polyatomic molecules has been achieved experimentally and theoretically. Now we are striding ahead in unraveling the mechanistic photophysics and photochemistry of large systems in biology and material.…”

Optimizing conical intersections of solvated molecules: The combined spin-flip density functional theory/effective fragment potential method

“…For comparison, the CI geometry obtained by the MRCI method is also included. 88 The CNNC torsion angle is nearly 90 • , and the two NCH 3 groups are decoupled. One of the CN bonds is stretched by 0.02 Å, and the other is shortened by 0.02 Å.…”

“…Since azomethane is the simplest molecule in the azo family, both experiments and theoretical calculations have been reported. [84][85][86][87][88][89][90] Before describing the CI points of hydrated azomethane, consider the accuracy of the present implementation of SFDFT/EFP1 analytic energy gradients. The analytic gradient was calculated for the azomethane · 2(H 2 O) cluster.…”