Dynamics mechanism of optical-optical double-resonant multiphoton ionization of nitrogen dioxide

The optical-optical double-resonant multiphoton ionization (OODR-MPI) spectrum of NO2 molecule in the 460-605-nm wavelength region of the probe photon is presented. The mechanism of the OODR-MPI of NO2 molecule is analyzed. The results show that the resonant features can be assigned to the transitions from the first 3sσg Rydberg intermediate resonant state to the final npσu Rydberg series. The ionization pathway is NO2 (X A1) (?) 3sσg (?) npσu (?) NO2 e. It is found that the converging potential of the npσu Rydberg series and the quantum defect of np orbit about NO2 are (78803±14) cm-1 and 0.652±0.014, respectively. The bending vibration frequency of 5pσu state is determined also.     

一类特殊广义Kac—Moody代数虚根决定的反射与Weyl群间的关系

对有限型李代数ｇ（Ａ）,相应于每个根ａ的反射ｒａ均在ｇ（Ａ）的Ｗｅｙｌ群Ｗ中,当ｇ（Ａ）为可对称化的不定型Ｋａｃ－Ｍｏｏｄｙ代数时,若ａ为一虚根且（ａ,ａ）〈０,则亦可定义反射ｒａ,并有ｒａ∈－Ｗ或ｒａ是－Ｗ中元与一个图自同构之积,本文给出了一类秩为３的广义Ｋａｃ－Ｍｏｏｄｙ代数的虚根系,然后讨论了一类特殊的广义Ｋａｃ－Ｍｏｏｄｙ代数的虚根决定的反射与Ｗｅｙｌ群之间的关系。     

NO2分子的光学-光学双色双共振多光子离化谱

以Nd:YAG激光器的二倍频输出光为抽运光,其三倍频输出抽运的光学参量发生/放大器输出光为探测光,利用光学-光学双色双共振多光子离化光谱技术(OODR-MPI),获得了NO₂分子在605—675nm探测光波长范围内的多光子离化激发谱. 通过对NO₂分子离化机理的分析,确定了在此波长区间,NO₂分子经1+3+1双共振多光子过程离化,离化通道为NO₂(X²A₁)hν 关键词： 2')" href="#">NO₂ 光学-光学双共振多光子离化谱 里德伯态 分子常数     

Theoretical analysis on the efficiency of optical-optical double-color double-resonance multiphoton ionization

Analytic formula of the efficiency of optical-optical double-color double-resonance multi-photon ionization （OODR-MPI） is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the influence of characteristic of the pump and probe laser on the ionization efficiency of （1＋2＋1） OODR-MPI process is simulated theoretically. It is shown that the pump laser will affect the ionization efficiency by the number control of the molecules excited to the first resonance state. The ionization efficiency is decided by the probe laser directly. Both of the excited molecules and ionization efficiency increase with the intensity and pulse duration of the laser until saturation. It is also found that the longer the delay time of the probe laser to the pump one is, the lower the ionization efficiency would be. The delay time ought to be smaller than the lifetime of the excited molecule in the practical use of the OODR-MPI technique.     

NO(3+1)共振增强的多光子离化谱

用皮秒脉冲高功率Nd∶YAG激光器抽运的光学参量发生/放大器作激发源,获得了NO分子在420～500 nm波长范围内的多光子离化谱,光谱图呈现分离谱的特征,表明在该波长区间NO分子以多光子共振方式离化。离化信号随激光强度的近四次方变化关系表明,在420～500 nm波长范围内NO分子吸收4个光子而离化。通过对谱线的标识,首次分离出NO分子以E 2Σ激发电子态为中间共振态的(3+1)多光子离化光谱序列,由谱线序列峰值波长得到NO分子E 2Σ电子态的振动常数,从而实现了采用多光子离化技术对该态能级结构的实验研究。     

Resonance-enhanced multi-photon ionization spectrum of NO in 575-680 nm wavelength region

The multi-photon ionization spectrum of NO in the wavelength region of 575-680 nm is obtained with an optical parameter generator and amplifier (OPG/OPA) pumped by a picosecond Nd:YAG laser as radiation source. The banded structure of the spectrum indicates that NO molecule is ionized in resonant manner and the peaks of the spectrum are assigned to the transition of NO molecule from the ground electronic state to A2∑(v' = 0,1,2,3), E2∑(v' = 0,1,2), F2Δ(v' = 0,1,2,3) and H2∑(v' = 0,1,2) intermediate resonant ones. The molecule constants about NO (A2∑, E2∑, F2Δ, H2∑) states are calculated from the center wavelength of the spectrum. It is also found that owing to the special electron configuration of NO, this molecule does not follow the normal transition selection rule of the diatomic molecule during the multi-photon process.     

NO2分子的光学-光学双色双共振多光子离化谱

以Nd:YAG激光器的二倍频输出光为抽运光，其三倍频输出抽运的光学参量发生/放大器输出光为探测光，利用光学-光学双色双共振多光子离化光谱技术(OODR-MPI),获得了NO₂分子在605—675nm探测光波长范围内的多光子离化激发谱. 通过对NO₂分子离化机理的分析，确定了在此波长区间，NO₂分子经1+3+1双共振多光子过程离化，离化通道为NO₂(X²A₁)hν     

Influence of laser intensity on the double-resonance multiphoton ionization process of NO molecule

The analytic formula of the ionization efficiency in the process of double resonance enhanced multi-photon ionization （DREMPI） is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the ionization efficiency and the laser power index versus laser intensity in the DREMPI process of NO molecule, via A2E and S2E intermediate resonant states, is numerically simulated. It is shown that the ionization efficiency of NO molecule increases with the laser intensity until getting saturation, while the laser power index decreases with the enhancement of the laser intensity and changes to zero at last. The variation of the laser power index with the laser intensity indicates that the ionization efficiency reaches saturation in the one, two, and three excitation steps respectively. It is also found that the narrower the laser pulse duration is, the higher becomes the laser intensity for saturation.     

一类特殊广义Kac-Moody代数虚根决定的反射与Weyl群间的关系(英)

对有限型李代数g（A）,相应于每个根α的反射r_α均在g（A）的Weyl群W中．当g（A）为可对称化的不定型Kac－Moody代数时,若α为一虚根且（α,α）＜0,则亦可定义反射r_α并有r_α∈－W或r_α是－W中元与一个图自同构之积（见[3]）．本文给出了一类秩为3的广义Kac－Moody代数的虚根系,然后讨论了一类特殊的广义Kac－Moody代数的虚根决定的反射与Weyl群之间的关系．     

NO分子光声光谱的理论分析

采用拉普拉斯变换严格求解二能级系统光与物质相互作用的速率方程,获得了强激光诱导气体分子系统光声信号的解析表达式。结果显示光声信号的大小与样品分子的吸收截面、激发光强度、分子共振跃迁吸收的光子数、分子碰撞弛豫速率等因素有关。借助于光声信号随激光强度的变化关系,将NO分子在420.0～470.0 nm波长区间的激光诱导光声光谱归属于NO分子经X 2Π→A 2Σ的双光子激发跃迁及X 2Π→E 2Σ,F 2Σ,R 2Σ的三光子激发跃迁,由此获得NO分子A 2Σ,E 2Σ,F 2Σ和R 2Σ激发电子态的振动常数分别为2 346,2 342,2 397和2 381 cm-1,结果与采用其他方法测量的结果符合得较好。并对光声信号随缓冲气压升高而出现饱和的现象进行了理论解释。