基于拉曼泵浦-探测光谱的冷原子温度估算

提出了基于拉曼泵浦-探测技术得到的原子吸收谱线获取冷原子温度的方案,并将其应用于85Rb原子磁光阱中。实验中,原子在囚禁光和探测光的共同作用下发生受激拉曼跃迁,产生亚自然线宽的类色散峰,通过把该类色散峰与理论模型进行拟合估算出被囚禁85Rb冷原子团的温度为230μK。相对于飞行时间测温法,该方案提供了一种简捷的测量冷原子温度的方法。

用于超快泵浦-探测光谱技术的异步光学采样(特邀)

异步光学采样(ASOPS)泵浦-探测光谱技术作为一种具有飞秒时间分辨的超快测量技术,能够快速捕捉超快动力学现象,是研究微观粒子行为的有力工具。对传统ASOPS的基本原理、系统组成展开具体分析,并着重讨论了该系统搭建的技术细节,总结了近年来传统ASOPS的研究与发展,最后展望了基于ASOPS的泵浦-探测光谱技术。

A New kHz Velocity Map Ion/Electron Imaging Spectrometer for Femtosecond Time-Resolved M olecular Reaction Dynamics Studies

A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method. By combining a kHz pulsed valve and an ICCD camera, this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz, totally compatible with the fs Ti：Sapphire laser system, facilitating time-resolved studies in gas phase which are usually time-consuming. Time-resolved velocity map imaging study of NH3 photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H＋NH~ products provides rich information about the dissociation dynamics of NH3. These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods.

Ultrafast Dynamics of Water Molecules Excited to Electronic ■ States:A Time-Resolved Photoelectron Spectroscopy Study

The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O (D2O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F1A1 state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F1B1 state decays through the F1A1 state via Coriolis interaction.

Ultrafast Decay Dynamics of 2-Hydroxypyridine Excited to S_(1) Electronic State

The S_(1) state decay dynamics of 2-hydroxypyridine following UV excitation at a wavelength range of 276.9-250.0 nm is investigated using femtosecond time-resolved photoelectron imaging technique.Based on pump wavelength dependence of the decay dynamics,a refined decay picture is proposed.At pump wavelength of 276.9 nm,the S_(1) state is depopulated through intersystem crossing to lower triplet state(s).At 264.0 nm,both intersystem crossing to lower triplet state(s)and internal conversion to the ground state are in operation.At 250.0 nm,internal conversion to the ground state becomes dominated.

电子自旋弛豫时间测量中电子自旋扩散的影响

在光注入电子自旋包的不同位置进行时间分辨的泵浦-探测实验时,发现电子自旋信息的退化率不同.揭示了电子自旋扩散对准确测量电子自旋弛豫时间的影响,获得了自旋输运动力学方程的解.对该解进行研究发现,电子自旋扩散对电子自旋弛豫时间测量值的影响可以归结为两个含时间的因子,其中一个因子与泵浦光斑中心和探测光斑中心的距离有关,另一个因子与泵浦光斑尺寸有关.提出了自旋弛豫时间测量实验中消除扩散影响的条件:1)泵浦光斑和探测光斑中心重叠;2)泵浦光斑尺寸足够大.结果表明,泵浦光斑尺寸越大,探测光斑中心越接近于泵浦光斑的中心,则扩散对自旋弛豫时间测量值所造成的影响就越小.

有机纳米材料光电子轨道断层成像技术

光电子轨道断层成像是有机纳米材料研究中一种实验和理论相结合的技术,其核心是建立光电子角分布能谱和分子初始态轨道结构之间的直接联系。研究者通过较为简易的平面波近似,可以实现对表面共轭分子价带轨道角分辨光电子能谱的精确分析,从而研究它们的电学、光学和化学特性。介绍了光电子轨道断层成像技术的理论基础和实验手段,综述了近年来该技术在确定分子的几何结构、测量界面电学相互作用、获得时间分辨轨道图像等领域的诸多应用,并介绍了该技术结合超快激光等相关实验技术的最新进展。