本文選題：激發(fā)態(tài)動力學 + 光電子影像　； 參考：《中國科學院研究生院(武漢物理與數(shù)學研究所)》2016年博士論文

【摘要】：分子激發(fā)態(tài)動力學過程在環(huán)境科學、生命科學、材料科學等領(lǐng)域發(fā)揮著重要作用,比如臭氧層的形成和保持、光合作用、分子開關(guān)等。分子激發(fā)態(tài)動力學過程包含發(fā)光、內(nèi)轉(zhuǎn)換、系間交叉、振動弛豫、解離、異構(gòu)等,這些過程發(fā)生的時間尺度大都在皮秒至飛秒量級。飛秒時間分辨的質(zhì)譜技術(shù)和飛秒時間分辨的光電子影像技術(shù)具有飛秒量級的時間分辨能力,很適合用于實時跟蹤分子激發(fā)態(tài)動力學演化過程。本文利用飛秒時間分辨光電子影像技術(shù)研究了1,2,4-三甲苯分子的超快內(nèi)轉(zhuǎn)換動力學過程,利用飛秒時間分辨的質(zhì)譜技術(shù)研究了鄰碘甲苯分子的解離動力學過程。1,2,4-三甲苯及鄰碘甲苯是化工和生物合成中最為常見的分子,了解它們的光物理光化學反應機理有助于我們認識和理解它們在化工和生物合成中的反應機理。本論文的主要研究工作有：(1)1,2,4-三甲苯分子的S2→S1態(tài)超快內(nèi)轉(zhuǎn)換動力學過程研究。實驗中1,2,4-三甲苯分子吸收兩個400 nm的光子后被激發(fā)到S2態(tài)。通過光電子能譜上三個特征光電子能譜帶的強度隨泵浦-探測延遲時間的變化,實時觀察到1,2,4-三甲苯分子S2→S1態(tài)的超快內(nèi)轉(zhuǎn)換動力學過程。通過監(jiān)控母體離子信號隨泵浦-探測延遲時間的變化,我們測得S2態(tài)的衰減壽命約為72 fs,通過S2態(tài)內(nèi)轉(zhuǎn)換過程而布居的熱振動Sl態(tài)的壽命約為16.4 ps。和之前人們對苯、甲苯、二甲苯分子的研究結(jié)果比較發(fā)現(xiàn),甲基的取代數(shù)目越多,S1態(tài)的壽命越長,可能是因為甲基的取代阻礙了分子從S1態(tài)演化到S1/S0的錐形交叉區(qū),從而使壽命變長。(2)鄰碘甲苯分子的光解動力學研究。實驗中鄰碘甲苯分子吸收一個266 nm的光子后被同時激發(fā)到具有束縛態(tài)特征的ππ*態(tài)和具有排斥態(tài)特征的no*態(tài)上。利用強800 nm光作為探測光,通過多光子電離的方法實時跟蹤解離過程。通過記錄母體離子信號及解離生成的碎片信號隨泵浦-探測延遲時間的變化,我們發(fā)現(xiàn),鄰碘甲苯分子的激發(fā)態(tài)衰減過程是一個非常快的過程,時間尺度約為100 fs,反映的是初始布居πσ*態(tài)的衰減動力學,同時還在解離碎片信號上觀察到了一個上升組分,它反映的是鄰碘甲苯分子的光解動力學過程,時間尺度約為380 fs。此外,我們利用基態(tài)碘原子的共振波長298.23nm作為探測光,利用共振多光子電離的方法選擇性地探測了解離生成基態(tài)碘原子的解離通道,測得生成基態(tài)碘原子的平均解離時間約為400 fs。
[Abstract]:The kinetic process of molecular excited states plays an important role in the fields of environmental science, life science and material science, such as the formation and maintenance of the ozone layer, photosynthesis, and molecular switches. The kinetic processes of molecular excited states include luminescence, internal conversion, intersystem cross, vibrational relaxation, dissociation, isomerism and so on. The time scale of these processes is large. Both from picosecond to femtosecond order of time. Femtosecond time resolved mass spectrometry and femtosecond time resolved photoelectron imaging technology have the time resolution ability of the femtosecond order of time. It is very suitable for real-time tracking of the dynamic evolution process of molecular excited states. In this paper, the 1,2,4- three toluene molecule is studied by the femtosecond time resolved photoelectron image technology. The kinetic process of fast internal conversion, using femtosecond time resolved mass spectrometry to study the dissociation kinetics of O iodide molecules,.1,2,4- tri trimethyl benzene and O iodide are the most common molecules in chemical and biosynthesis. Understanding the mechanism of their photometric chemical reactions helps us to understand and understand them in chemical and biological processes. The main research work in this paper is: (1) the study of the ultrafast internal conversion kinetics of S2 to S1 states of 1,2,4- three toluene molecules. In the experiment, the 1,2,4- three toluene molecule absorbs two 400 nm photons and is excited to the S2 state. The intensity of the photoelectron energy spectrum band on the photoelectron spectroscopy is delayed by the pump detection delay. The ultrafast internal conversion process of the 1,2,4- three toluene molecule S2 to S1 state is observed in real time. By monitoring the change of the pump detection delay time, the decay life of the S2 state is measured to be about 72 FS, and the lifetime of the thermal vibrational Sl state in the S2 state transition process is about 16.4 PS. and the people before it. The results of the study of benzene, toluene and xylene found that the longer the number of methyl substituted, the longer the lifetime of the S1 state, may be because the replacement of the methyl group hindered the evolution of the molecule from the S1 state to the conical cross region of the S1/S0, thus making the life longer. (2) the photodissociation kinetics of the o-ioditoluene molecule. The 266 nm photons are stimulated at the same time in the no* state with the characteristic of the bound state and the characteristic of the rejection state. Using the strong 800 nm light as the detection light, the dissociation process is tracked through the multiphoton ionization method. By recording the changes of the matrix ion signal and the dissociated fragment signal with the pump detection delay time, we It is found that the decay process of the excited state of the o iodide molecule is a very fast process, the time scale is about 100 fs, reflecting the decay kinetics of the initial pion sigma state, and also a rising component is observed on the dissociated fragment signal, which reflects the photodissociation kinetics of the o iodide molecule, with a time scale of about 380 FS. In addition, we use the resonance wavelength 298.23nm of the ground state iodine atom as the detection light, using the resonance multiphoton ionization method to selectively detect the dissociation channel of the iodine atoms from the ground state, and the average dissociation time of the generated ground state iodine atom is about 400 fs..

【學位授予單位】：中國科學院研究生院(武漢物理與數(shù)學研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O561

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