Optical time-resolved study of the excitation dynamics*

Transient behaviour of the excited states originated from the neutral and the charged species is discussed using data from time-resolved experiments. Complex transient characteristics obtained for the slightly charged poly-(bithiophene) film during electrochemical doping were explained in terms of sequential molar fraction changes of the neutral species, the radical cation and the π-dimerized radical cations. Femtosecond transient absorption measurement carried out in time range of 0-4 ns for a two-photon excited dye reveals a multi-exponent decay with well separated relaxation times and the distinct relaxation mechanisms. At high irradiance and a sufficient fluence, the multi-photon excitation processes affect the subpicosecond response and lead to formation of the photo-products.     

Cs(6D5/2)+H2→CsH[ X1Σ+(v,J)]+H转动分辨总截面的测量

利用泵浦-检测方法,在样品池条件下,研究了Cs(6D5/2)与H2反应碰撞传能过程。利用激光感应荧光（LIF）光谱技术,确定了CsH[X1Σ+(v,J)]振转能级上的布居分布,转动态分布与热统计分布基本一致.Cs激发态原子密度由激光能量吸收得到.记录A1Σ+(v',J+1)→X1Σ+(v,J)的时间分辨荧光,从荧光强度的对数值给出的直线斜率确定(v',J+1)→(v,J)的自然辐射率,结合(v,J)→(v',J+1)吸收系数的测量,得到反应生成物CsH[X1Σ+(v,J)]态的分子密度.由速率方程分析,给出反应截面(v,J),对J求和,得到(v)[10-16cm2单位]分别为（0.64±0.19）（v=0）和（0.58±0.17）（v=1）.     

Rb与H_2的反应碰撞:Rb(6~2D)+H_2→RbH+H

在样品池条件下,应用脉冲激光的泵浦-检测技术,研究了Rb(6~2D)激发态原子与H_2反应碰撞生成的RbH分子的振转能级的布居数密度分布及平均转动能、振动能、平动能的相对比值.发现RbH(X~1∑~+)只有v=0,1上有布居.转动带分布轮廓与池温下的统计分布接近,得到RbH的Boltzmann转动温度稍低于池温,而振动温度高.v=1和v=0上的布居数之比约为0.69,从而得到RbH(X~1∑~+)上平均转动能和平均振动能,由反应的有效能得到平均平动能,这三种能量的相对比值f_R:f_V:     

Time-resolved studies of ultrafast wavepacket dynamics in hydrogen molecules

Recent advances in the study of quantum vibrations and rotations in the fundamental hydrogen molecules are reported. Using the deuterium molecules (D₂⁺ and D₂) as exemplars, the application of ultrafast femtosecond pump-probe experiments to study the creation and time-resolved imaging of coherent nuclear wavepackets is discussed. The ability to study the motion of these fundamental molecules in the time-domain is a notable milestone, made possible through the advent of ultrashort intense laser pulses with durations on sub-vibrational (and sub-rotational) timescales. Quantum wavepacket revivals are characterised for both vibrational and rotational degrees of freedom and quantum models are used to provide a detailed discussion of the underlying ultrafast physical dynamics for the specialist and non-specialist alike.     

Probing Molecular Dynamics with Ultrafast Electron Diffraction?

Recent progress in ultrafast lasers,ul-trafast X-rays and ultrafast electron beams has made it possible to watch the motion of atoms in real time through pump-p...     

InP纳米颗粒的超快动力学和光学非线性

通过飞秒泵浦-探测方法测量了波长为800 nm时InP半导体纳米颗粒激发态的瞬态动力学过程。观察到一个快速的光致漂白建立和一个漂白的恢复过程,分析饱和吸收的来源可能是带填充效应引起跃迁的饱和吸收。对于漂白恢复中的快过程是由于自由载流子的弛豫,而慢成分是由于光激发载流子在很短的时间内受陷于表面态形成的限域载流子的弛豫。通过飞秒光克尔效应(OKE)方法测量材料的超快非线性响应曲线,计算了材料的光学三阶非线性极化率,分析了非线性的来源。     

利用飞秒泵浦探测技术研究碘甲烷B态预解离动力学

应用飞秒双光泵浦-探测技术结合飞行时间质谱研究了碘甲烷分子的B态预解离动力学，其中泵浦光波长为400 nm，探测光为800 nm，碘甲烷主要的产物通道为生成CH3I+和CH3+．改变泵浦与探测光之间的延时，得到了这两种离子的时间演化曲线，每个曲线都可以用两个指数函数来拟合，拟合常数为?1和?2，?1反映了碘甲烷分子吸收三个泵浦激光所到达的高里德堡态的动力学，?2反映了吸收两个泵浦激光所到达的B里德堡态的动力学，得到的B态的带源寿命为1.57 ps，这个值和以前的文献非常符合，试验结果被解释为多光子的电离解     

Predissociation Dynamics of B State of Methyl Iodide with Femtosecond Pump-probe Technique

The predissociation dynamics of B Rydberg state of methyl iodide is studied with femtosecond two-color pump-probe time-of-°ight spectra at pump pulse of 400 nm and probe pulse of 800 nm. The dominant product channels are the CH3I+ and CH3+ formation. The time-dependent signals for CH3I+ and CH3+ ions are obtained. Both of the signal curves can be ˉtted by biexponential decays with time constants of ?1 and ?2, ?1 is assigned to the lifetimes of high Rydberg states, which can be accessed by absorbing three 400 nm pump pulses and ?2 re°ects the dynamics of B Rydberg state, which is accessed with two pump pulses. The lifetime of B Rydberg state is determined to be about 1.57 ps, which is incredibly consistent with the previous studies. The results were interpreted as a multiphoton dissociative ionization processes.     

飞秒泵浦-探测实验中量子拍频现象的数据处理

The pump-probe experiments for 1,3-dichlorobenzene in gas phase have been performed by femtosecond multiphoton ionization mass spectra at a pump pulse of 270 nm and a probe pulse of 810 nm by using our homebuilt femtosecond laser system. The models for the exponential process and quantum beat are presented to extract the photodissociation dynamics information from the data. A fitting and analyzing software which is programmed by graphical language LabVIEW has been developed for the experimental data. The Convolution, Levenberg Marquardt,and Deconvolution mathematics VIs of LabVIEW are used in this program to make the program much simpler than using other programming languages. The experimental data have been well fitted with this program. The results provide the lifetime of excited-state S1 and the frequency of quantum beat.     

Studies of Photoionization of CF3 I by Femtosecond Time-resolved Mass Spectrometry

The multi-photon dissociative photoionization dynamics of CF3I has been studied with femtosecond two-color pump-probe time of flight mass spectra at a pump pulse of 265 nm and a probe pulse of 398 nm. The life constants of CF3I+ and its fragment ions CF3+ and I+ are obtained as (96±7), (198±130) and (167±6)fs, respectively. The multi-photon dynamics leading to these ions differ. CF3I+ corresponds to a (1+2′) transition with one-photon pump excitation to the A band of CF3I. CF3+ are mainly formed by a tow-photon probe excitation to the CF3+ with subsequent dissociation of parent ions. I+ are produced in (2+2′) combined with (1+1′+2′) process. The results provide information on the multi-photon pathways involved.