【作者】 徐晏琪；

【导师】 张冰；

【作者基本信息】 中国科学院研究生院（武汉物理与数学研究所） ， 原子与分子物理， 2013， 博士

【摘要】 分子激发态动力学和离子态光谱都是激光化学研究的重要内容。通过对分子激发态动力学和离子态光谱的研究,可以获得分子的激发态和离子态信息,为我们深入了解化学反应的实质提供依据。具有飞秒时间尺度分辨率是飞秒时间分辨光电子影像技术的一大特点,可以实现对分子激发态动力学行为的实时观察。而质量分辨阈值电离光谱作为高分辨的离子态光谱可以实现质量分辨。本文将飞秒时间分辨的光电子影像技术运用于碘乙烷的激发态动力学研究,而将质量分辨阈值电离光谱技术运用于3,4-二氟苯甲醚和间甲氧基苯乙烯的离子态光谱研究。主要工作可以分为三个部分。第一部分利用飞秒时间分辨光电子影像技术和飞秒时间分辨质谱技术研究碘乙烷的激发态动力学。实验测得当分子吸收一个267nm光子后被激发到解离带A带,运用飞秒时间分辨质谱技术测得A带对应的时间常数为57fs。母体分子在吸收两个400nm光子的情况下,可以被激发到B带,对应的预解离寿命为1.42ps。当分子吸收三个400nm光子后会到达更高里德堡态,通过时间分辨光电子能谱分布观察到更高里德堡态会快速转移到B带,这一过程所对应的时间尺度为50fs。第二部分利用共振增强双光子电离(R2PI)和质量分辨的阈值电离光谱(MATI)技术来研究顺式和反式3,4-二氟苯甲醚S1和Do态的振动光谱。从实验中测得顺式和反式3,4-二氟苯甲醚S1←S0跃迁能的带源分别为35505±2和35711±2cm-1,它们各自的绝热电离势分别为67780±5和68125±5cm-1。并且发现3,4-二氟苯甲醚的S1←So跃迁能和绝热电离势的能移都存在着加法定则。这一定则对于光谱学家在研究涉及多取代苯的衍生物的实验中选取合适的扫描范围很有帮助。通过比较3,4-二氟苯甲醚Sl和D0态的振动光谱,发现分子D0←S1跃迁中倾向于保持原有的振动模式,这表明分子的两种构型D0态的分子构型,对称性和振动坐标都与S1态类似。第三部分利用共振增强双光子电离(R2PI)和质量分辨的阈值电离光谱(MATI)技术来研究间甲氧基苯乙烯四个构型的S1和D0态的振动光谱。从实验中测得四个异构体Sl←So跃迁能的带源分别为32767±2,32907±2,33222±2和33281±2cm-1。它们的绝热电离势分别为65391±5,64977±5,65114±5和64525±5cm-1。通过比较间甲氧基苯乙烯与对甲氧基苯乙烯的MATI光谱发现对于一些面内环振动来说,振动频率除了依赖于振动模式以外,还依赖于两个取代基的相对位置。更多还原

【Abstract】 Molecular excited state dynamics and ionic spectroscopy are the important components of laser chemistry. Research of excited state dynamics and ionic spectroscopy can help us to obtain more information of the excited states and ionic states of the molecules. Femtosecond time resolution is an important feature of femtosecond time-resolved photoelectron imaging. It makes the real-time investigating of the dynamics of molecules to become a reality. Mass Analyzed Threshold Ionization Spectroscopy (MATI) is a powerful technique for studies of molecular ions and can offer a very high resolution with mass resolved.Excited state dynamics of Iodine ethane has been investigated by femtosecond time-resolved photoelectron imaging. The ionic spectroscopies of3.4-difuoroanisole and m-methoxystyrene have been investigated by mass analyzed threshold spectroscopy. The dissertation is mainly composed of three parts:The first part is the study of ultrafast dynamics of electronically excited states in ethyl iodine using femtosecond timeresolved photoelectron imaging coupled with mass spectroscopy. The dissociation constant of the A band was measured to be about57fs. Upon two400nm photon excitation to the B band, the time evolution of the parent ion with consists of two components. The fast component with a time constant of50fs revealed the energy transfer from the higher Rydberg states to the B band. The slow one was determined to be1.42ps, which was due to predissociation relaxation from the B band to the repulsive A band.The second part is the vibronic and cation spectra of3,4-difluoroanisole recorded by R2PI and MATI techniques. The band origins of the S1S0electronic transition of the cis and trans rotamers appear at35505±2and35711±2cm-1and the adiabatic ionization energies are determined to be67780±5and68125±5cm-1, respectively. We find that there may have an additivity rule associated with the energy shifts in the E1and IE of3,4-difluoroanisole. This rule may be useful for spectroscopists to make an initial guess in setting proper scanning ranges of their lasers for their experiments involving multiple substituted benzenes. Analysis of the obtained vibronic and cation spectra shows that a propensity rule maintaining the same vibration in the D0←S1transition exists. This indicates that the molecular geometry, symmetry, and vibrational coordinates of the cation in the Do state are like those of the neutral species in the Si state for both cisandtransrotamers of3,4-difluoroanisole. In addition, investigations on the frequencies of the active vibrations suggest that the geometry is more rigid in the cationic Do state than that in the neutral S1state.The Third part is the vibronic and cation spectra of m-methoxystyrene recorded by R2PI and MATI techniques. The band origin of the S1←S0electronic excitation for conformer a, b, c, and d of m-methoxystyrene are found to be32767±2,32907±2,33222±2, and33281±2cm-1. And, the adiabatic IE are determined to be65391±5,64977±5,65114±5, and64525±5cm-1, respectively. Analysis on the MATI spectra of m-methoxystyrene and p-methoxystyrene shows that the frequencies of these in-plane ring vibrations depend on the relative location two substituent groups on the aromatic ring as well as the vibrational pattern.更多还原