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Vibrational Dynamics of Electronic Excited Molecules

电子激发分子的振动动力学

基本信息

批准号：
13640518
负责人：
TSUCHIYA Soji
金额：
$ 1.6万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640518/
关键词：
Vibronic State Acetylene Anharmonic coupling Photodissociation Predissociation 前期解離

项目摘要

Vibrational and reaction dynamics of electronic excited acetylene have been investigated.1. The vibrational level structure of acetylene in the electronic excited A^^〜 state was believed to be the progressions of the 2^n3^m vibrational states. However, in this work it was proved that the V_3' mode couples anharmonically with the ungerade v_4'/v_6' mode to form a polyad structure composed of the 2^m3^n, 2^m3^<n-1>(4/5)^2, 2^m3^<n-2>(4/6)^4, ………. The same type of the anharmonic coupling was found for the ungerade vibrational states which were investigated by an IR-UV double resonance spectroscopy. In this case, the (4/6) states having odd quantum numbers couple with the 3^n state.2. The predissociation rate constants of acetylene in respective rovibronic levels of the A^^〜 state were determined through observation of the spectral line-widths. The rate constants were found to be independent of the vibrational parity gerade or ungerade. This can be attributed to the anharmonic coupliig between the V_3' and V_4'/V_6' modes which causes the gerade and ungerade states to have a similar vibrational chracteristics.3. It was found that the triplet state-mediated predissociation of excited acetylene toward C_2H(X^^〜)+H ceases around the excitation energy of 51100 cm^<-1> which is far beyond the adiabatic dissociation threshold of the A state. At this energy, acetylene still predissociates at a rate of around 10^<10> s^<-1> to form C_2H(A^^〜) + H.4. A new experimental technique, Differential Temperature Laser Induced Fluorescence Spectroscopy, was developed which is capable of separating overlapping cold and hot bands of a LIF spectrum.

研究了电子激发乙炔的振动和反应动力学。电子激发A^~态中乙炔的振动能级结构被认为是2^n3^m振动态的演化。然而，本工作证明了V_3‘模与非简并的V_4’/V_6‘模的非调和耦合形成了由2^m~3^n，2^m~3^&lt；n-1&gt；(4/5)^2，2^m~3^&lt；n-2&gt；(4/6)^4，………组成的多元结构。用红外-紫外双共振光谱研究了非晶态振动，发现了相同类型的非谐耦合。在这种情况下，具有奇量子数的(4/6)态与3^n态耦合。通过对谱线宽度的观察，确定了乙炔在A^^~态各振动态的预解离速率常数。结果表明，速率常数与振动宇称或非振动宇称无关。这可以归因于V_3‘和V_4’/V_6‘模之间的非简谐耦合，使得激射态和非激射态具有相似的振动特性。结果表明，在激发能为51100 cm~(-1)&gt；时，激发态乙炔对C_2H(X^~+)+H的三重态预解离停止，远远超过A态的绝热离解阈值。在此能量下，乙炔仍以约10^~(-1)~(-1)~(-1)的速率预解离生成C_2H(A^~)+H_4。发展了一种新的实验技术--差温激光诱导荧光光谱，它能够分离激光诱导荧光光谱中重叠的冷带和热带。