Ultrafast Imaging of Electronic Relaxation in Ortho-xylene： New Features from Fragmentation-Ion Spectroscopy  

作　　者：刘玉柱 KNOPP Gregor 肖韶荣 GERBER Thomas 

机构地区：[1]College of Physics and Opto-electronics Engineering, Nanjing University of Information Science & Technology, Nanjing 210044 [2]Paul Scherrer Institute, Villigen 5232, Switzerland

出　　处：《Chinese Physics Letters》2014年第12期130-133,共4页中国物理快报（英文版）

基　　金：Supported by the National Natural Science Foundation of China under Grant No 11304157, and the Swiss National Centre of Competence in Research-Molecular Ultrafast Science and Technology （NCCR-MUST）.

摘　　要：After light absorption, a molecule can undergo ra- diationless processes, and photophysics is one of the important general types. The photophysical pro- cesses involve internal conversion （IC） due to elec- tronic nonadiabaticity and intersystem crossing （ISC） induced by spin-orbit coupling. In polyatomic molecules that are excited IC and ISC to vibronic to higher electronic states, levels of lower electronic states are two dominant mechanisms. With the ad- vent of femtosecond ultrashort pulse, tracking and controlling the ultrafast photophysical processes be- come realizable. Due to the fact that ISC requires a change in the spin of an electron, it is usually a slower process than IC. However, extensive reports show that ultrafast competing ISC exists in a number of systems. Re- cently, Richter et al. reported femtosecond ISC in cytosine. Martinez-Fernandez et al. simulated the deactivation dynamics of photo-excited 6-thioguanine using a direct surface hopping dynamics approach Their simulations show that 6-thioguanine is another example of a system showing ultrafast ISC that can compete with IC in the same time scale. Both the spin-orbit and the dynamic couplings are important to describe realistically the excited state dynamics of 6-thioguanine. A similar phenomenon has also been evidenced in the S1 state of benzene. The exper- imental results show that the ultrafast decay of the S1 state is due to competing IC and ISC processes and both processes occur on a femtosecond timescale. Spin-orbit coupling is highly effective when the in- volved states are nearly isoenergetic.After light absorption, a molecule can undergo ra- diationless processes, and photophysics is one of the important general types. The photophysical pro- cesses involve internal conversion （IC） due to elec- tronic nonadiabaticity and intersystem crossing （ISC） induced by spin-orbit coupling. In polyatomic molecules that are excited IC and ISC to vibronic to higher electronic states, levels of lower electronic states are two dominant mechanisms. With the ad- vent of femtosecond ultrashort pulse, tracking and controlling the ultrafast photophysical processes be- come realizable. Due to the fact that ISC requires a change in the spin of an electron, it is usually a slower process than IC. However, extensive reports show that ultrafast competing ISC exists in a number of systems. Re- cently, Richter et al. reported femtosecond ISC in cytosine. Martinez-Fernandez et al. simulated the deactivation dynamics of photo-excited 6-thioguanine using a direct surface hopping dynamics approach Their simulations show that 6-thioguanine is another example of a system showing ultrafast ISC that can compete with IC in the same time scale. Both the spin-orbit and the dynamic couplings are important to describe realistically the excited state dynamics of 6-thioguanine. A similar phenomenon has also been evidenced in the S1 state of benzene. The exper- imental results show that the ultrafast decay of the S1 state is due to competing IC and ISC processes and both processes occur on a femtosecond timescale. Spin-orbit coupling is highly effective when the in- volved states are nearly isoenergetic.

分 类 号：O413.1[理学—理论物理] TQ245.23[理学—物理]