Ultrafast nonadiabatic photoisomerization dynamics of a light-driven molecular motor

• 1、Key Laboratory for Quantum Information and Quantum Optoelectronic Devices, Shaanxi, and Department of Applied Physics, Xi’an Jiaotong University, Xi’an 710049, China
• 2、Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101 Shandong, China

Abstract：With trajectory surface-hopping dynamics at the semi-empirical OM2/MRCIlevel, photoisomerization dynamics of a light-driven molecular rotary motor is investigated in gas phase. A meanlifetime of the S$_{1}$ excited state for the M structure (see Figure 1 in the text) is about 580 fs in gas phase.The dynamical process of electronic de-excitation is followed by the twisting about the centralC=C double bond and the out of plane motion of pyramidalization. Two S$_{1}$/S$_{0}$ conical intersections (CI) are found, and de-excitation from the S$_{1}$ excited state occurs at these two CI. Since the difference betweenthe energy barriers on these two routines, the de-excitation mainly occurs at one CI named as CI$_{1}$.The quantum yield of the M-P photoisomerization of this molecular motor is about 63.6% in our calculation.Although the averaged lifetime of the M structure was close to 600 fs, our calculated fluorescence emission spectrum shown that the fluorescence emission nearly disappeared after 100 fs, which means that most of molecules arrived at ``dark state" after 100 fs. Our calculatation result about fluorescence emission spectrum agrees well with the experimental result of Feringa et al.

keywords： Atomic and molecular physics Light-driven molecular motor Photoisomerization Nonadiabatic molecular dynamics Quantum yield

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