Computerized System of Multiphoton Ionization Spectroscopy

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三氯乙烯分子的多光子电离解离研究

用可调谐染料激光器 ,在 4 5 0— 4 75 nm范围内 ,在飞行时间质谱仪上研究了三氯乙烯分子的共振增强多光子电离解离过程。研究表明 ,在此实验波段内三氯乙烯分子经历了从 π到 3d里德堡态的 (3 1 )多光子过程 ,可以用母体离子阶梯开关模型对三氯乙烯的电离解离过程进行解释 ,并对振动能级进行了标识 ,对振动频率进行了计算     

CF自由基双光子共振增强多光子电离研究：3pRy dberg态的转动分析

利用Ar/CF4、Ar/CF2Cl2或Ar/CF3COOH混合气体的直流脉冲放电产生CF自由基,观测了260～360nm范围内转动分辨的CF自由基双光子共振增强多光子电离谱。分析表明,该段光 谱对应于CF自由基3pπD2Πr(ν'=2～6,r=3/2,1/2)←←X2Πr(ν"=0,r=3/2,1/2)的共振激发。对观测的振动带进行了转动分析,并获得了3p里德堡态的转动常数和自旋-轨道分裂值。     

Study of Microwave Multiphoton Transition of Rydberg Potassium Atom by Using B-Spline

Abstract The B-spline expansion technique and time-dependent two-level approach are applied to study the interaction between the microwave field and potassium atoms in a static electric field. We obtain theoretical multiphoton resonance spectra that can be compared with the experimental data. We also obtain the time evolution of the final state in different microwave fields.     

Study of Microwave Multiphoton Transition of Rydberg Potassium Atom by Using B-Spline

The B-spline expansion technique and time-dependent two-level approach are applied to study the interaction between the microwave field and potassium atoms in a static electric field. We obtain theoretical multiphoton resonance spectra that can be compared with the experimental data. We also obtain the time evolution of the final state in different microwave fields.     

多光子电离下醇类团簇中的反应

应用Nd:YAG(Spectra-Physics LAB-170)脉冲激光器输出的355nm紫外激光实现了对甲醇、乙醇及正丙醇的多光子电离,对每一种样品通过质谱技术都观测到了两个质子化团簇离子系列:(R..3OH)nH 和(R1,2,3OH)n(H2O)H (R1,2,3代表CH2、CH2CH2及CH2CH3CH2),结合在HF/STO-3G和B3LYP/6-31G 水平上的从头计算对其反应通道做了分析,发现其产生经过了团簇内部的质子转移反应及离子-分子反应,且质子主要来自于羟基上的氢离子.并结合从头算分析了(R1,2,3OH)nH 的结构,给出了幻数团簇(R1,2,3OH)3H 的构型.同时对(R1,2,3)n(H2O)H 系列只在n值较大时出现做了相应的解释.     

铕原子Rydberg态的场电离研究

利用三步激光共振激发结合场电离探测技术,系统地研究了铕原子归属于第一电离限4f76s 9S4的4f76snp Rydberg态的场电离过程,得到了铕原子4f76snp Rydberg 态的场电离光谱图。在光激发之后施加脉宽为0.2μs的脉冲电场,连续扫描电压得到场电离过程图。从4f76snp Rydberg态的场电离过程图谱中,可以精确地获得态的场电离阈,观察电场逐步从0到3 kV变化时原子的演化过程。特别是,受黑体辐射的影响,一些结构出现在了场电离光谱图上。     

Laser Excitation Spectroscopy of the Jet-Cooled Methoxy Radical Amidst Hydroxyl Transitions

Abstract

Laser-induced fluorescence excitation spectra of the methoxy radical have been recorded under high resolution in a supersonic jet expansion. The rotational structure associated with the 3¹ ₀ band of methoxy has been identified in the midst of strong overlapping rotational transitions due to the hydroxyl radical in the 32240 - 32580 cm^?1 spectral region. Rotationally-resolved à ²A₁ – [Xtilde] ²E spectra of the 3¹ ₀ band of methoxy have been explicitly assigned using the nomenclature for prolate symmetric top transitions in doublet states.     

NO分子共振增强的多光子离化机制

用皮秒Nd：YAG激光器泵浦光学参量发生／放大器做激发源,获得了420～480nm波长范围内NO分子的多光子离化谱。通过对谱线的归属,分析确定了NO分子的离化为以A^2∑为中间共振态的(2 2)共振增强的多光子离化过程。以速率方程为基础,利用激光脉宽较窄(35ps)的条件,推导出离化信号随激光强度呈近四次方变化关系,与实验测量结果相符,这可为用共振增强多光子离化(REMPI)光谱技术探测污染物NO分子提供实验参考。     

355nm激光作用下丁酮多光子电离质谱信号分析

为研究由氢键形成的超分子体系内的质子化构型,利用355nm共振增强多光子电离(REMPI)技术结合飞行时间质谱(TOF-MS)得到丁酮多光子电离系列团簇质谱.实验没有观测到丁酮母体的团簇信号,只测到丁酮解离、异构后的异丙醇团簇离子,为丁酮解离、异构提供了很有意义的实验数据.     

乙腈和氨水团簇的激光电离实验研究

在355nm激光波长下应用多光子电离和分子束技术研究了乙腈和氨水的混合团簇,所得的团簇离子以(CH3CN) n、(CH3CN)nNH 3和(CH3CN)n(NH3) 为主,中性团簇以二元团簇(CH3CN)n(NH3)m/(CH3CN)n(NH4OH)m为主.离子产物是来源于中性的二元团簇先吸收部分激光能量解离成稳定的小团簇和碎片,然后再发生分子蒸发和电离的过程,并未发生明显的质子转移反应.     

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。     

甲胺分子共振增强多光子电离的波长依赖性

使用激光多光子电离质谱技术，研究了甲胺分子在４２５ｎｍ－４９５ｎｍ波长范围内共振增强多光子电离碎裂过程，记录了母体离子和与碎片离子产额与波长的依赖关系。由于共振增强多光子电离母体离子与碎片离子谱的相似性，可用探测总离子信号的方法来替代单独的母离子探测，有效地提高痕量探测的灵敏度。     

Ionization of Rydberg atoms by the kicks of half-cycle pulses

We present a quantum mechanical model to study the ionization of quasione-dimensional Rydberg atoms interacting with half-cycle pulses (HCPs) and use it to demonstrate the inadequacy of semiclassical approaches to calculate ionization probabilities of such atoms subject to the impact of more than one HCP. For a single-kicked atom both models correctly reproduce the experimentally observed ‘s-curve’ as can be seen by plotting the ionization probability P as a function of momentum transfer q₁. We demonstrate that for a twice-kicked atom, the semiclassical model yields numbers for P which are not physically realizable. For fixed values of momentum transfers q₁ and q₂, in a twice-kicked atom, the ionization probability as a function of time delay between the kicks exhibits periodic decay and revival. The results of the semiclassical approach appear to agree with the quantum mechanical values at the times of revival of P, else these show considerable deviation. We attempt to provide a physical explanation for the limitation of the semiclassical approach.     

乙胺分子的多光子电离过程质谱研究

报道了乙胺分子在４４０～４７５ｎｍ波长范围内多光子电离（ＭＰＩ）质谱（ＭＳ）研究结果。碎片离子主要由母体离子碎裂模式产生。母体离子ＣＨ３ＣＨ２Ｎ＋·Ｈ２由经３ｓ里德堡态的（２＋２）共振多光子电离产生后，大部分发生β键断裂，形成ＣＨ２＝Ｎ＋Ｈ２离子，还有一部分再吸收一个光子，通过Ｃ－Ｈ（ＣＨ２）键的断裂产生了ＣＨ３ＣＨ＝Ｎ＋Ｈ２离子。ＣＨ３ＣＨ＝Ｎ＋Ｈ２和ＣＨ２＝Ｎ＋Ｈ２离子最容易发生的碎裂过程是脱去氢分子，分别产生Ｃ２Ｈ４Ｎ＋（分子式）离子和ＣＨ≡Ｎ＋Ｈ离子。     

Multiphoton Ionization of Potassium Atoms in Femtosecond Laser Fields

We study the multiphoton ionization of potassium atoms in 800 nm and 400 nm femtosecond laser fields.In the 800 nm laser field,the potassium atom absorbs three photons and emits one electron via one photon resonance with the 4p intermediate state with the help of the ac-Stark shift.The resonance feature is clearly shown as an Autler-Townes(AT) splitting and is mapped out in the electron kinetic energy spectrum.In a 400 nm laser field,although one photon resonance is possible with the 5p state,no splitting is observed.The different transition amplitudes between 4s-4p and 4s-5p explain the observed results.Due to the AT effect,an unexpected peak in the photoelectron energy spectrum that violates the dipole transition rule is observed.A preliminary explanation involving the spin-orbit interaction in the p state is given to account for this component.The observed ATsplitting in the electron kinetic energy distribution can be used as an effective method to calibrate the intensity of a laser field.