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 

作者机构：College of Physics and Opto-electronics Engineering Nanjing University of Information Science & Technology Nanjing 210044 Paul Scherrer Institute Villigen 5232 Switzerland 

出 版 物：《Chinese Physics Letters》 (中国物理快报（英文版）)

年 卷 期：2014年第31卷第12期

页      面：130-133页

核心收录：

学科分类：081702[工学-化学工艺] 07[理学] 0809[工学-电子科学与技术（可授工学、理学学位）] 070205[理学-凝聚态物理] 08[工学] 0817[工学-化学工程与技术] 0805[工学-材料科学与工程（可授工学、理学学位）] 0704[理学-天文学] 0702[理学-物理学] 

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) 

主　　题：Ultrafast Imaging Electronic Relaxation Fragmentation-Ion Spectroscopy 

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.