2-甲基吡嗪分子激发态系间交叉过程的飞秒时间分辨光电子影像研究  

Intersystem crossing of 2-Methlypyrazine studied by femtosecond photoelectron imaging

作　　者：布玛丽亚·阿布力米提[1,2] 凌丰姿 邓绪兰 魏洁 宋辛黎 向梅 张冰[2] Bumaliya Abulimiti;Ling Feng-Zi;Deng Xu-Lan;Wei Jie;Song Xin-Li;Xiang Mei;Zhang Bing(College of Physics and Electronic Engineering,Xinjiang Normal University,Urumqi 830054,China;State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics and Mathematics,Chinese Academy of Sciences,Wuhan 430071,China)

机构地区：[1]新疆师范大学物理与电子工程学院,乌鲁木齐830054 [2]中国科学院武汉物理与数学研究所,波谱与原子分子物理国家重点实验室,武汉430071

出　　处：《物理学报》2020年第10期110-117,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11564040,21763027);新疆维吾尔自治区自然科学基金(批准号:2017D01B36,2016D01A058);新疆维吾尔自治区区域协同创新专项(批准号:2019E0223);新疆维吾尔自治区天山青年计划项目(批准号:2018Q072);新疆维吾尔自治区高校科研计划项目(批准号:XJEDU2020Y029);新疆师范大学“十三五”校级重点学科招标项目(批准号:17SDKD0602);新疆师范大学本科教学质量工程建设教学研究与改革项目(批准号:SDJG2019-27)资助的课题.

摘　　要：飞秒时间分辨光电子影像技术和飞秒时间分辨质谱技术相结合,研究了2-甲基吡嗪分子电子激发态超快非绝热弛豫动力学.用323 nm光作为泵浦光,把2-甲基吡嗪分子激发到第一激发态S1,用400 nm光探测激发态演化过程.通过时间分辨质谱技术测得S1态的寿命为98 ps.实验中,实时观察到了单重态S1向三重态T1的系间交叉过程.通过分析发现,跟吡嗪分子S1态的动力学过程不同,2-甲基吡嗪分子激发到S1态后,不仅S1→T1系间交叉过程是S1态主要衰减通道,S1→S0内转换过程也是S1态另一个主要衰减通道.发挥飞秒时间分辨光电子影像技术的优点,实验上得到不同泵浦-探测时间延迟的光电子角分布,从角分布信息结合光电子能谱信息,尝试观察2-甲基吡嗪分子的非绝热无场准直,但由于2-甲基吡嗪分子对称性比吡嗪分子更低,对称性更低分子准直现象的观察更有挑战性,在实验中未能观察到非绝热准直动力学.本工作为2-甲基吡嗪分子S1态非绝热弛豫动力学提供了较清楚的物理图像.The ultrafast nonadibatic relaxation dynamics of the excited state of 2-methylpyrazine has been studied by using femtosecond time-resolved photoelectron imaging and femtosecond time-resolved mass spectrometry.The first excited state S1 of 2-methylpyrazine was excited by 323 nm pump light,and the excited state deactivation process is detected by 400 nm probe light.The lifetime of S1 state 98 ps is obtained by time-resolved mass spectroscopy.The intersystem crossing from the S1 state to the T1 state is observed on real time.The relaxation dynamics of S1 state of 2-methlypyrazine is different from that of pyrazine,the results show that the intersystem crossing process between S1 and T1 is the main relaxation channel of S1 state of 2-methlypyrazine,but the internal conversion process between S1 and S0 is also a main relaxation channel of S1 state.By using the advantages of femtosecond time-resolved photoelectron imaging,the photoelectron angular distribution at different pump-probe time delay was obtained experimentally.From the photoelectron angle distribution combined with photoelectron kinetic energy distributions,we tried to observe the field-free nonadiabatic alignment.However,due to the fact that the molecular symmetry of 2-methylpyrazine is lower than that of pyrazine,it is more challenging to observe the phenomenon of molecular nonadiabatic alignment with lower symmetry.Therefore,it is fail to observe nonadiabatic alignment feature of 2-methylpyrazine in this experiment.This work provides a clearer physical picture for S1 state nonadibatic relaxation dynamics of 2-methylpyrazine.

关 键 词：甲基吡嗪 光电子影像 系间交叉 泵浦-探测 时间分辨光谱 

分 类 号：O626[理学—有机化学]