飞秒分辨差异吸收光谱技术难点的研究

项目名称： 飞秒分辨差异吸收光谱技术难点的研究

项目编号： No.60808011

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 数理科学和化学

项目作者： 张苏娟

作者单位： 西北大学

项目金额： 24万元

中文摘要： 分子领域的超快动力学过程基本都在亚皮秒量级，分秒分辨差异吸收光谱是打开这个领域之门的钥匙。但分秒分辨差异吸收光谱的获得受到颇多的技术限制，首先是宽光谱超快光源的获得；其次是解决光源的涨落带给实验结果的致命影响；第三针对超快光源的脉冲峰值的超强特点带给分光光路以及探测器的特殊要求；最后还有一点就是分光光路造成脉冲的啁啾现象带给实验时间结果上的重大影响。针对以上技术难点，我们分别进行了突破研究。目前的研究结果为：将光参量放大器（OPA）内产生的种子白光用二向色镜分离出可见波段（这部分光本身不参与参量放大过程）用作飞秒探测光；采用网状光栅的空间分光方法给探测光引入一路参考光用于实时校正探测光的涨落；脉冲光的超强峰值功率决定探测器必须经高强度衰减后采用面阵探测器进行探测（避免饱和）；啁啾现象引起的对时间结果影响采用数据计算分析的方法予以校正。目前的的实验结果能达到1%的校正结果。并利用这套系统对菠菜LHCII的单聚体，二聚体，三聚体生物样品进行了色素分子间的传能研究。

中文关键词： 时间分辨;超快光谱;探测光;参考光

英文摘要： In the field of molecular dynamics, the time constants always is in picosecond. Femotesond-resolved transient spectrum is the effect key to explore these process. But there are many diffeculties to get femotesond-resolved transient spectrum. Firstly, it is so expensive to obtain broadwide spectrum of ultrafast pulsed light. Secondly, the fluctuation of ultrafast pulsed light is so high that the signal is always is drown in it. Thirdly, the peak intensity of ultrafast pulsed laser is very high, which always bring special diffculties to the optical lens and the detector; Finally, the chirp phenomenon of pulsed light when they going through optical lens will bring deviations to the time constants. Based on these technical problems stated above, we find solutions one by one. The major resulted can be stated as: Firsty, pulsed broaden light was derived from the seeds pulse in OPA( the visible waveband itself does not participate in parametric amplification process),which can be used as probe pulse(or reference pulse). Secondly, as in the case of fluctuation of pulsed light, two beams are generally required to measure the variation of transmittance in the excited volume. Meshy grating was used to derived these two beams which must have the same spectral distribution. One pulse is spatially and temporally overlapped to the excitation pulse and has the function of the probe. The other passes through the sample in a different position and has the function of the reference beam. The detector can be a CCD camera coupled to a flat field monochromator and an attenuator. The derivation of time constant resulted from Chirp phenomenon was corected by analysis and calculating method. At present, the amplitude fluctuation of pulsed light can be calibrated toless than 1% in our experimental equipment. Using this system, Eenergy transfer between pigments in LHC II subcomplexes, monomer, homotrimer, heterotrimer and aggregate were studied.

英文关键词： time-resolved; transient spectrum; probe light; reference light