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

Abstract

Cyclopropanone exhibits an intriguing phenomenon that the fluorescence from the S(1) state disappears below 365 nm. This is ascribed to the ultrafast S(1) → S(0) internal conversion process via conical intersection, which deprives opportunity of the fluorescence emission. In this work, we have used ab initio based surface hopping dynamics method to study vibrational-mode-dependent S(1) → S(0) internal conversion of cyclopropanone. A new conical intersection between the S(1) and S(0) states is determined by the state-averaged CASSCF/cc-pVDZ calculations, which is confirmed to play a critical role in the ultrafast S(1) → S(0) internal conversion by the nonadiabatic dynamics simulations. It is found that the internal conversion occurs more efficiently when the initial kinetic energies are distributed in the four vibrational modes related to the C═O group, especially in the C-O stretching and the O-C-C-C out-of-plane torsional modes. Meanwhile, the S(1) lifetime and the time scale of the S(1) → S(0) internal conversion are estimated by the ab initio based dynamics simulations, which is consistent with the ultrafast S(1) → S(0) internal conversion and provides further evidence that the ultrafast internal conversion is responsible for the fluorescence disappearance of cyclopropanone.

Identification of unavoided crossings in nonadiabatic photoexcited dynamics involving multiple electronic states in polyatomic conjugated molecules

“…[9][10][11][12][13] Furthermore, ab initio NA-MD have been successfully applied to study ultrafast photoinduced electron transfer (ET) processes 14,15 in quantum dots, 16,17 and Auger phenomena including multiple exciton generation and recombination. 18 Among these methods, trajectory surface hopping algorithms have proven to be efficient techniques to describe the photochemistry of a variety of organic molecules such as benzene, 19 fulvene, azulene, 20 nucleobases, [21][22][23] poly(phenylene ethynylene) dendrimers, 74,75 formamide, 24 silaethylene, 25 ethylene, 26 azobenzene, 27,28 azomethane, 29 cyclopropanone, 30 and pyrrole 31,32 among others. Complexity a) Author to whom correspondence should be addressed.…”

Photoinduced reactions of chloroacetone in solid Ar: Identification of CH 2 COClCH 3

“…After prolonged irradiation the bands from group C were clearly discernible, as shown in Figure 1(b). The photodissociation of cyclopropanone was studied experimentally [25] and theoretically [26][27][28]. Thomas and Rodriguez found that CH2=CH2 and CO were the only volatile products resulted upon excitation at a selected wavelength between 292 to 365 nm [25].…”

“…and S0 states of cyclopropanone using the state-averaged CASSCF method; one leads to an α-bond fission and the other to two α-bond fissions [27,28]. phase, CH2COCH3 was detected [8].…”

Generalized trajectory surface-hopping method for internal conversion and intersystem crossing

“…[1][2][3] It is attractive because it is easy to implement and offers an intuitive interpretation, and it has thus been adopted by many groups. [4][5][6][7][8][9][10][11][12][13][14][15][16] It has been applied to study many ultrafast photophysical and photochemical processes in the gas phase and the condensed phase. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Despite the growing popularity and success of the trajectory-based FSSH method, it remains approximate and has some well-known drawbacks.…”