高等植物外周捕光天线LHCⅡ中的超快光动力学过程

利用飞秒抽运探测技术及时间分辨荧光(TRPL)等光谱技术对高等植物LHCⅡ中的超快光动力学过程进行了研究。在其时间分辨荧光光谱中表现出了明显的各向异性特性。实验上观察了LHCⅡ中色素间的能量传递过程,由飞秒动力学发现,单体内Chlb到邻近的Chla之间的能量传递在200～300fs的时间尺度,Chla激子带间的能量弛豫发生在几百飞秒,不同单体Chla分子间能量分布过程在几个皮秒。而时间分辨荧光和飞秒动力学过程中上百皮秒的慢过程归属于不同聚集体间的能量平衡过程或分子构象变化。     

2004-2005年度胡刚复、饶毓泰、叶企孙、吴有训、王淦昌物理奖介绍

1饶毓泰物理奖 项目名称：飞秒时间分辨光谱技术及超快光子学新材料研究 主要完成人：龚旗煌(北京大学物理学院)该项目总结了龚旗煌和由他领导的研究集体1991年至2003年间，立足于国内在飞秒光谱及应用和材料非线性光学性质研究中取得的成果．如建立了飞秒时间分辨荧光上转换实验平台，研究了三乙胺酸分子的荧光衰变特性．验证了该类分子激发态无势垒异构理论(CFO理论)；     

钛蓝宝石飞秒超快光谱技术及其应用进展

介绍飞秒激光技术的进展、钛宝石飞秒激光放大技术及飞秒分辨相关测量技术.并介绍了飞秒分辨光荧光上转换和光克尔实验技术及其在各种学科中的应用. 关键词： 飞秒激光 飞秒光谱 光克尔 光荧光     

噁嗪750激光染料分子在醇类溶剂中超快动力学研究

利用飞秒时间分辨荧光亏蚀光谱技术,研究了噁嗪750激光染料分子在典型的醇类溶剂中超快动力学过程.实验发现两个超快动力学过程:飞秒量级的快速弛豫过程和皮秒量级的慢速弛豫过程.快速弛豫过程来源于分子内振动能量再分配(IVR)和溶剂分子超快惯性弛豫动力学过程,而慢速弛豫过程对应于溶剂化的扩散分子弛豫动力学过程.实验结果表明慢速弛豫过程的时间常数随醇溶剂分子间氢键键能的增强而增大.     

激光应用 激光生物学

Q631 2005010188 PSⅡ颗粒复合物飞秒分辨低温荧光动力学研究=Study on femotosecond fluorescence dynamics of photosystem Ⅱ particle complex at low temperature[刊,中]／刘晓(中科院西安光机所瞬态光学技术国家重点实验室．陕西,西安 (710068)).王水才…∥光子学报．-2004．33(2)．-216- 220 采用飞秒时间分辨荧光光谱学对PSⅡ颗粒复合物在 83 K.160 K,273 K下进行研究．实验表明随温度升高,光谱加宽。并且发现在PSⅡ颗粒复合物中至少存在9种特征Chl分子。在不同的温度下,参与能量传递的色素分子     

具有电子推拉结构的多支化分子的光物理特性的研究

利用稳态光谱和飞秒时间分辨荧光亏蚀的技术,研究了不同溶剂中一系列有分子内电荷转移特性的分子的结构与光物理性质的关系,研究体系为三苯胺作为电子给体,2,1,3-苯并噻二唑作为受体的单支分子及其对应的两支和三支分子. 并结合TD-DFT计算进一步解释了实验中所观察到的现象. 三个分子相似的吸收和荧光光谱以及强的溶剂依赖光谱特性表明两支与三支分子激发态与单支分子相似,表明激发态都定域在其中一支上. 激发时多支分子内发生多维电荷转移,然后快速地定域到某一支上发射. 另一方面多支分子相对于单支分子吸收和发射光谱的红     

飞秒超快光谱技术及其互补使用

超快光谱技术是研究物质激发态过程的重要手段,本文对飞秒时间分辨荧光技术和飞秒泵浦探测技术这两个重要的超快光谱技术进行了详细介绍,阐述了系统的原理、光路及数据处理方法,给出了不同的实现方法并比较了其优缺点。最后通过一个实例说明这两个技术的互补性,通过结合使用两个系统,能够对科学问题进行更全面可靠的研究。     

Fe~(3+)对石墨烯氧化物荧光淬灭机理的研究

采用改进的Humer法合成了石墨烯氧化物,利用搭建的时间分辨光谱探测系统详细探究了Fe~(3+)(浓度为0.5、1、2 mmol/L)对石墨烯氧化物荧光淬灭物理机制。稳态荧光发射光谱中,随着Fe~(3+)浓度的增加,石墨烯氧化物的荧光强度急剧减弱。时间分辨荧光光谱和飞秒瞬态吸收光谱研究证实,加入不同浓度Fe~(3+)的GO其动力学衰减曲线基本没有任何变化。结果表明,Fe~(3+)对石墨烯氧化物的荧光淬灭主要是静态的荧光淬灭过程。     

超快微光分子光谱探测技术研究

按照超快极微弱分子吸收光谱学,荧光光谱学,时间分辨光谱学以及偏振荧光光谱学探测特性,设计、集成组建了能够探测紫外－可见－红外快到飞秒时间分辨的单分子光学事件的激光瞬态光谱仪.其光源有从300 nm到3000 nm连续可调的飞秒激光器、纳秒氢灯及连续氙灯.光谱分辨率达0.05 nm,在泵浦探测差异吸收下有小于150 fs的时间分辨率.谱仪能够实时给出光谱曲线及生物分子组分寿命.利用该谱仪探测了PSⅡCC,PSⅡRC的能量传递动力学.在83 K温度下PSⅡCC中的β-Car分子接收507 nm光能,以单步跃迁和随机转移的方式通过Chl a641.5637/638分子传递光能到反应中心Chl a683.2680/681,平均传能时间为77 ps,有59.94％的组分用355 ps时间电荷重组.在PSⅡRC中的β-Car分子接收507 nm光能,由Chl a641.5637/638分子传递光能通过Chl a678.2675.5到反应中心,平均传能时间为88.5 ps.在83 K温度下,反应中心复合物离子对;P680+·pheo-］平均再复合寿命为19.35 ns.     

飞秒时间分辨拉曼光谱用于研究β-胡萝卜素单重激发态内转换和振动弛豫过程

搭建了飞秒时间分辨受激拉曼光谱(FSRS)装置,并用于研究全反式β-胡萝卜素单重电子激发态超快内转换和振动弛豫过程.基于三脉冲“抽运-探测”方案搭建的时间分辨受激拉曼光谱装置同时实现了150fs的时间分辨率和23.7cm^-1的光谱分辨率,光谱检测范围为300—4000cm^-1.对全反式β-胡萝卜素电子激发态的飞秒时间分辨拉曼光谱研究表明,β-胡萝卜素被激发到S₂态后,经由寿命约为0.3ps的中间态S_X态实 关键词： 飞秒时间分辨拉曼光谱 β-胡萝卜素 激发态内转换 振动弛豫     

单脉冲飞秒激光时域参数测量技术研究

钛宝石飞秒激光放大系统具有重复频率低、脉冲波形复杂等特点,为准确测量其峰值功率,提出对单次脉冲波形和脉冲宽度测量的需求。介绍了单脉冲飞秒激光时域波形和脉冲宽度的测量原理和测量方法,设计了基于频率分辨光学开关法的单脉冲飞秒激光时域参数测量装置。讨论了单脉冲飞秒激光时域参数测量校准面临的问题及解决方法。     

Quantum state measurement using coherent transients

We present the principle and experimental demonstration of time resolved quantum state holography. The quantum state of an excited state interacting with an ultrashort chirped laser pulse is measured during this interaction. This has been obtained by manipulating coherent transients created by the interaction of femtosecond shaped pulses and rubidium atoms.     

Realignment process of actin stress fibers in single living cells studied by focused femtosecond laser irradiation

Three-dimensional dissection of a single actin stress fiber in a living cell was performed based on multi-photon absorption of a focused femtosecond laser pulse. The realignment process of an actin stress fiber was investigated after its direct cutting by a single-shot femtosecond laser pulse irradiation by high-speed transmission and fluorescence imaging methods. It was confirmed that mechanical force led by the femtosecond laser cutting propagates to entire cell through the cytockelton in a 100 μs time scale. The cut actin stress fiber was realigned in the time scale of a few tens of minutes. The dynamic analysis of the realignment induced by single-shot femtosecond laser gives new information on cell activity.     

Analysis of the halo background in femtosecond slicing experiments

The slicing facility FemtoSpeX at BESSY II offers unique opportunities to study photo‐induced dynamics on femtosecond time scales by means of X‐ray magnetic circular dichroism, resonant and non‐resonant X‐ray diffraction, and X‐ray absorption spectroscopy experiments in the soft X‐ray regime. Besides femtosecond X‐ray pulses, slicing sources inherently also produce a so‐called `halo' background with a different time structure, polarization and pointing. Here a detailed experimental characterization of the halo radiation is presented, and a method is demonstrated for its correct and unambiguous removal from femtosecond time‐resolved data using a special laser triggering scheme as well as analytical models. Examples are given for time‐resolved measurements with corresponding halo correction, and errors of the relevant physical quantities caused by either neglecting or by applying a simplified model to describe this background are estimated.     

时间分辨光谱法用于离体人肺鳞癌,腺癌及正常组织的荧光寿命测量

用Ｎｄ：ＹＡＧ倍频光５３２．０ｎｍ泵浦ＤＣＭ染料输出的６３２．８ｎｍ激光作激发源，通过时间分辨法测得离体人肺腺癌，鳞癌及正常组织的特征峰荧光寿命分别为５．１，５．６和６．３ｎｓ实验结果表明：肿瘤组织的荧光寿命总小于正常组织的荧光寿命，这种方法将有可能用于精确诊断和定位肿瘤。     

Refractive index measurement by spectrally resolved interferometry using a femtosecond pulse laser

We describe a measurement method of refractive indices by way of spectrally resolved interferometry using a femtosecond pulse laser. The method is dispersion insensitive and requires no prior precise knowledge of the geometrical thickness of the specimen. Not only the group but also the phase refractive index can be determined over the wide spectral range covered by the optical comb of the femtosecond pulse laser in use.     

Quantum state tomography of dissociating molecules

Using tomographic reconstruction we determine the complete internuclear quantum state, represented by the Wigner function, of a dissociating I2 molecule based on femtosecond time resolved position and momentum distributions of the atomic fragments. The experimental data are recorded by timed ionization of the photofragments with an intense 20 fs laser pulse. Our reconstruction method, which relies on Jaynes's maximum entropy principle, will also be applicable to time resolved position or momentum data obtained with other experimental techniques.     

Femtosecond laser-induced stimulation of a single neuron in a neuronal network

We demonstrated the stimulation of neurons at a single-cell level in cultured neuronal network by a focused femtosecond laser. When the femtosecond laser was focused on a neuron loaded with a fluorescent calcium indicator, the fluorescence intensity immediately increased at the laser spot, suggesting that intracellular Ca²⁺ increases in the neuronal cell due to the femtosecond laser irradiation. The probability of Ca²⁺ elevation at the laser spot depended on the average laser power, irradiation time, and position of the focal point along the optical axis, indicating that the femtosecond laser activates neurons because of multiphoton absorption. Moreover, after laser irradiation of a single neuron cultured on multielectrode arrays, the evoked electrical activity of the neurons was demonstrated by electrophysiological systems, which concluded that the focused femtosecond laser could achieve stimulating a single neuron in a neuronal network with high spatial and temporal resolution.     

利用非锁定飞秒激光实现太赫兹频率的精密测量

频率是电磁波最重要的一个基本物理量,随着THz技术的发展,在光源研制、宽带通信、超精细光谱测量等领域都对THz频率的高精度侧量提出了要求.传统的Fabry-Perot干涉法与外差探测法难以实现THz频率的高精度测量,频率梳方法虽然测量精度很高,但测量系统复杂.本文提出一种利用重复频率自由漂移的飞秒激光器实现太赫兹频率精密测量的新方法.通过对非锁定的飞秒激光器的重复频率和THz拍频频率进行同时连续采集与计算,得到被测THz频率,测量精度可以达到10~(-10)量级无需对飞秒激光重复频率进行复杂的锁定控制,测量系统大大简化.