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题名	基于强太赫兹辐射的氢及其同位素分子离子解离控制研究
作者	贾正茂
学位类别	博士
答辩日期	2014
授予单位	中国科学院上海光学精密机械研究所
导师	徐至展院士，曾志男研究员
关键词	分子解离，氢分子离子，太赫兹，动力学。
其他题名	Research on the dissociation control of H+2 and its isotopes in strong THz electric fields
中文摘要	近几十年，控制化学反应或光激发/电离过程中电子和其他分子碎片的运动一直是科学研究的热点。控制分子碎片运动的一个重要目的是选择性地断开或链接某一化学键，从而控制化学反应的产物。随着飞秒激光技术的发展，特别是载波包络相位稳定的少周期强场脉冲激光的出现，使得利用激光脉冲控制分子的解离和化学反应过程成为可能。 作为自然界中最简单的分子离子，氢及其同位素分子离子只有两个核和一个电子，使得氢及其同位素分子离子的理论研究不需要采用单电子近似，其结果与实验具有直接可比性，也能更简洁地反映其中的物理本质。本文利用中心波长为228纳米的超短紫外脉冲将氢及其同位素分子离子中的电子激发至解离态，然后利用中心波长为25.6微米的载波包络相位稳定的太赫兹脉冲控制解离态电子的运动，最终控制氢及其同位素分子离子的解离过程，主要内容和创新点包括： 1. 获得极高的解离控制率。利用超短紫外脉冲和太赫兹脉冲的合成场，可以实现氢分子离子99.3%的解离控制率，此时体系的总解离率为6.14%，更为重要的是，体系的总电离率几乎为零。对HD+和HT+而言，体系的解离控制率也可以达到99.2%和99.0%，此时体系总的解离率分别为5.91%和6.04%。 2. 提出了有效解离控制时间的概念。有效解离控制时间指的是对任何一种分子而言，都存在一段解离控制的有效时间，在该时间段内，外界电场可以有效地控制分子解离的产物。分子的有效解离时间与分子的质量有关，分子的质量越大，其有效解离时间越长。对氢分子离子而言，其有效解离控制时间为16.0 fs，对氧分子而言，其有效解离控制时间长达60.8 fs。 3. 总结了可以实现分子最大解离控制率的外场条件。只有当控制脉冲的半周期大于或与分子的有效解离控制时间相匹配时，才可以得到最好的解离控制率，否则控制脉冲电场方向的改变会影响解离控制的效果。此外激发脉冲的光强也会影响解离控制的效果。当激发脉冲的光强太高的时候，部分电子会被激发至3s 解离态，这会严重影响分子解离控制效果。 4. 利用外场的缀饰理论和经典力学的方法解释了分子解离局域化控制过程。对体系电离掉的电子而言，其运动由其电离时受到的外电场力决定，其运动方程与外电场力的方向相同；对解离态上的电子而言，外电场对体系的缀饰作用决定了其运动的方向，该方向与电子受到的外电场力的方向相反。
英文摘要	Coherent control of electrons and fragments of molecules in photochemical reactions has attracted a great deal of interest in the past decade. One of the main goals has been to find a way to selectively break and form molecular bonds in photochemical reactions. With the advent of new laser technologies, which have enabled generation of carrier envelope phase (CEP) stabilized few-cycle pulses and isolated subfemtosecond pulses, several control strategies have been proposed. Being the simplest molecule, H2+ and its isotopes have two nuclei and only one electron. There is no need to employ single electron approximation (SEA) in the theoretical modeling. The obtained results can provide deeper insight of the underlying physics. A 228-nm linearly polarized ultrashort ultraviolet (UV) pulse is used to excited the electrons to the dissociative states, then a time delayed linearly polarized 25.6- m CEP locked terahertz (THz) pulse is utilized to steer the motion of the electrons of dissociative states. The main results and innovative points are listed as following: 1. High dissociation control ratio. With the two laser pulses in UV and THz spectral regimes, a high localization probability of 99.3% of H2+ can be obtained, while the total dissociation probability is 6.14% and the total ionization probability is almost zero (less than 0.0013%). For HD+ and HT+, the dissociation control ratio can also reach 99.2% and 99.0%, respectively. The total dissociation probability is 5.91% and 6.04%, respectively. And the total ionization probability is near zero too. 2. Effective dissociation control time. For each molecule, there exists a time window during which the outer electric field can control the dissociation effectively, and this time period is called the effective dissociation control time. The time window is dependent on the mass of the molecule, the greater the quality, the longer the effective dissociation control time. For H2+, the control time lasts 16.0 fs, while for O2, the control time lasts as long as 60.8 fs. 3. Summarization of the conditions of the outer fields under which the maximum dissociation control ratio of molecules can be obtained. When the half period of the control pulse is larger than or match the effective control time of the molecule, one can get its best dissociation ratio, otherwise, the reverse of the control pulse electric field would break the effective dissociation control. Besides, the peak intensity of the exciting pulse influences the dissociation control too. When the intensity is too strong, more electrons can be excited onto the higher 3s state, which dramatically damages the electron localization control. 4. With the dress effect of the control pulse and classical methods, one can reveal the mechanism behind the whole dissociation process. For ionized electrons, their moving direction is determined by the direction of the electric force, while for electrons of the dissociation states, the dress effect of the control pulse determines their moving direction, which is opposite to that of the electric force.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15880]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	贾正茂. 基于强太赫兹辐射的氢及其同位素分子离子解离控制研究[D]. 中国科学院上海光学精密机械研究所. 2014.

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