叶绿素a分子在乙醇溶剂中的瞬态吸收研究

采用飞秒瞬态吸收方法研究叶绿素a分子在乙醇溶液的的激发态性质。观测到叶绿素a的Q带和B_y带的瞬态吸收谱。并且观测到了叶绿素a分子的两个超快动力学过程。认为一个来源于基态吸收谱的非均匀展宽,而另一个则来源于溶剂对于激发态分子结构变化的响应。同时,为了了解叶绿素a在乙醇溶剂中的各相异性,采用405nm激发叶绿素a分子得到了各相异性值为0.143,并通过模拟得到可能的θ_(da)、θ_(db)和η。     

金纳米粒子降低吸附态细菌叶绿素a荧光量子效率的机理研究

本文通过比较细菌叶绿素a(BChl a)吸附于Au纳米颗粒表面前后吸收光谱、荧光光谱、绝对量子产率和荧光寿命的变化,研究金纳米颗粒表面对吸附态细菌叶绿素a(BChl a)自发荧光辐射过程的影响。结果表明,BChl a吸附到Au纳米颗粒表面后,单体和二聚体BChl a吸收峰位均红移约3nm;BChl a单体发射的荧光峰位置从784nm红移到791nm,BChl a二聚体发射的荧光峰位置从684nm红移到689nm,二者荧光均发生淬灭;荧光量子效率降低;荧光寿命在误差范围内保持不变。原因可能来自两个方面:(1)BChl a吸附到Au导电表面后使得与自发辐射跃迁速率相关的光子能态密度变小,从而使BChl a自发辐射速率降低;(2)BChl a与纳米Au颗粒表面间的无辐射能量转移导致吸附态BChl a非辐射速率增大。     

基于CBERS-1影像监测太湖叶绿素a浓度的季节分布状况

叶绿素a浓度是衡量湖泊富营养化程度的重要指标。采用太湖2003年10月27日和28日的水质实验数据,构建了太湖叶绿素a浓度反演模型。然后将该模型应用于2006年4月5日、4月28日、5月16日、8月5日、10月30日和2007年7月5日的6期CBERS-1影像数据,研究与探讨了太湖叶绿素a浓度在上述时间尺度上的变化状况。通过研究可知,太湖叶绿素a浓度在夏季较低,而在秋季和冬季较高,基本上能反映浮游植物年际生长的4个过程;与以往的研究对比分析可知,基于CBERS-1影像数据反演获取的叶绿素a浓度比实际浓度总体偏高,CBERS-1数据影像在水色遥感中的应用仍然有待进一步的研究与探索。     

氢键效应对2,3-二氢-3-酮基-1H-吡啶并[3,2,1-kl]吩噻嗪光物理性质的影响

利用含时密度泛函理论(TDDFT)方法和飞秒时间分辨的瞬态吸收光谱技术对2,3-二氢-3-酮基-1H-吡啶并[3,2,1-kl]吩噻嗪(PTZ4)和3-酮基-1H-吡啶并[3,2,1-kl]吩噻嗪(PTZ5)这两种荧光探针分子的光物理性质进行了研究. TDDFT结果表明PTZ4和PTZ5在甲醇溶液形成了氢键络合物导致它们吸收峰的红移. PTZ4分子在基态有四种稳定构型,其在四氢呋喃溶液中的双荧光峰正是来自于四种构型下的内部电荷转移态. PTZ4分子在四氢呋喃和甲醇溶液中的瞬态吸收光谱表明,从局域态到转移态的弛豫时间常数在四氢呋喃中为16.0 ps,在甲醇中为7.5 ps;PTZ4分子在甲醇中的激发态寿命为53.8 ps,而这种超短的寿命可能是由于PTZ4分子在激发态时形成的面外型氢键络合物导致的.     

Eu3+、Tb3+与1-乙酰乙酰吲哚、1,10-邻菲啰啉二元、三元体系在溶液中荧光光谱研究

观察了以不同比例溶解在乙醇中的Eu3+、Tb3+、1-乙酰乙酰吲哚(HL)和1,10-邻菲啉(Phen)的荧光光谱.结果表明HL能有效地把吸收的能量传递给Tb3+,而不能有效地传递给Eu3+.讨论了HL和Phen对Eu3+、Tb3+的配位作用及其对Eu3+或Tb3+所组成的三元体系中敏化发光性能的影响.     

Eu~（3＋）、Tb~（3＋）与1－乙酰乙酰吲哚、1，10－邻菲啰啉二元、三元体系在溶液中荧光光谱研究

观察了以不同比例溶解在乙醇中的ＥＵ（３＋）、Ｔｂ（３＋）、１－乙酰乙酰吲哚（ＨＬ）和１，１０－邻菲啉（Ｐｈｅｎ）的荧光光谱．结果表明ＨＬ能有效地把吸收的能量传递给Ｔｂ（３＋），而不能有效地传递给Ｅｕ（３＋）．讨论了ＨＬ和Ｐｈｅｎ对Ｅｕ（３＋）、Ｔｂ（３＋）的配位作用及其对Ｅｕ（３＋）或Ｔｂ（３＋）所组成的三元体系中敏化发光性能的影响．     

在LiNbO3:Fe晶体中暗辐照对光束从自散焦向自聚焦转换过程的影响

基于二维带输运模型，研究了LiNbO3:Fe晶体中光束从自散焦向自聚焦动态转换过程.结果表明暗辐照在动态转换过程中起着非常重要的作用，当暗辐照较小时动态转换过程才发生.在暗辐照较小的情况还分析了热释电效应对动态转换过程的影响. 关键词： 光生伏打效应 暗辐照 自散焦 自聚焦 LiNbO3:Fe     

OCS分子在128 nm附近的光解动力学研究：S(3PJ=2,1,0)、S(1D2)以及S(1S0)产物通道

本文利用时间切片离子成像技术对OCS分子进行了真空紫外波段的光解动力学研究. 在四个光解光波长(从129.32到126.08 nm)下测量了硫原子解离产物S(³P_J=2,1,0)、S(¹D₂)、S(¹S₀)的速度影像,并从中清晰地发现了四个主要的解离产物通道：S(³P_J=2,1,0)+CO(X¹Σ⁺),S(³P_J=2,1,0)+CO(A³π),S(¹D₂)+CO(X¹Σ⁺)和S(¹S₀)+CO(X¹Σ⁺). 在实验影像中,产物CO分子的部分振动态结构能够得到分辨. 实验还获取解离产物总平动能谱,产物分支比和角分布. 对实验结果进行分析显示除绝热解离通道S(³P_J=2,1,0)+CO(A³π)之外,在其他三个产物通道中非绝热效应都起到非常重要的作用.     

BaFBr，BaFBr：Eu~（2＋）和BaFBr：Ce~（3＋）晶体在X射线辐照和光激励过程中发光和光电导的实时原位测量

在自建的多功能实时原位测量发光特性和光电导的实验装置上，测量了ＢａＦＢｒ，ＢａＦＢｒ：Ｅｕ２＋和ＢａＦＢｒ：Ｃｅ３＋单晶在Ｘ射线辐照和光激励过程中的发光强度和光电导。首次从光电导的角度测量到Ｘ射线辐照时，Ｅｕ２＋并没有被离化，而Ｃｅ３＋被离化，离化电子经导带被Ｆ＋心俘获；明确证实了光激励过程中Ｆ心电子的隧穿效应。     

二硫化碳分子在204 nm附近的光解离动力学研究：S(3PJ)+CS(X1Σ+)产物通道

本文用时间切片离子速度影像技术研究CS₂分子在204 nm附近的光解离动力学. 在201.36、203.10、204.85和206.61 nm这四个解离波长下,实验清楚地观测到S(³P_J)+CS(X¹Σ⁺)产物通道. 在实验获得的S(³P_J=2,1,0)影像中,对应的CS(X¹Σ⁺)产物的振动态结构得到了部分的分辨. 通过对影像的分析,还获得了解离的总平动能谱以及产物的各项异性参数. 实验观察到的相对小的各项异性参数表明产物更倾向于经历了间接的光解离过程. 这一通道的自旋－轨道禁阻特征也说明了非绝热效应在二硫化碳紫外光解离生成S(³P_J=2,1,0)+CS(X¹Σ⁺)的过程中发挥了重要作用.     

Rotational reorientation dynamics of Rhodamine 700 in different excited states

The rotational reorientation dynamics of rhodamine 700 (LD700) in the first (S₁) and the fifth (S₅) excited state in three aprotic polar solvents have been investigated using femtosecond time-resolved stimulated emission pumping fluorescence depletion (FS TR SEP TD) spectroscopy. In both excited states, the overall rotational relaxation of LD700 occurs on a time scale of 40-230 ps depending on the solvent, and a quantitative analysis of this time constant has been performed using the Stokes-Einstein-Debye (SED) hydrodynamic theory combined with the extended charge distribution model developed by Alavi and Waldeck. The experimentally measured reorientation times for LD700 in S₅ are smaller than those in S₁, which is in accord with the predictions by the SED theory. In addition, for LD700 in S₅, a rapid initial decrease on the time scale less than 0.5 ps has been found. According to our analysis, this fast component may account for the rapid internal conversion from S₅ to S₁, and the rate of internal conversion was found to be sensitive to the solvent polarity.     

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.     

DMSO溶剂中All-trans-astaxanthin激发态的飞秒时间分辨光谱

基于飞秒时间分辨瞬态吸收和多元瞬态光栅光谱技术对全反式Astaxanthin(AXT)在DMSO溶剂中的超快激发态弛豫动力学进行了观测.结果表明,光激发后AXT/DMSO体系直接发生S_0→S_2跃迁,基态漂白对应光谱范围为420~550nm.由S_2→S_1的内转换过程发生的时间常数为120~160fs.S_1态激发态吸收对应的光谱范围为550~740nm,基态漂白恢复过程对应的是S_1→S_0的内转换过程,其时间尺度为4.50~5.50ps.     

Internal Conversion Process of Chlorophyll a in Solvents in Femtosecond Pump-Probe Laser Fields

采用约化密度矩阵理论研究了溶液中叶绿素a分子的内转换过程. 内转换时间可以通过模拟实验荧光亏蚀光谱得到. 计算得到的叶绿素a分子在乙酸乙酯、四氢呋喃和二甲基甲酰胺溶剂中的内转换时间分别是141、147和241 fs. 理论分析表明：荧光亏蚀光谱曲线的振荡行为主要是由分子布居在耦合势能面间的振荡引起的. 分析了两个电子态之间非绝热耦合对内转换时间及荧光亏蚀光谱的影响,还讨论了叶绿素a分子与溶液耦合作用对内转换时间的影响.     

N-乙基吡咯S1态超快动力学：飞秒时间分辨光电子成像研究

N-乙基吡咯是吡咯分子的一个乙基取代衍生物,它的激发态衰变动力学目前为止很少被研究. 本文利用飞秒时间分辨光电子成像的实验方法研究N-乙基吡咯分子S₁态的衰变动力学. 实验采用241.9和237.7 nm的泵浦激发波长. 在241.9 nm激发下,得到5.0±0.7 ps,66.4±15.6 ps和1.3±0.1 ns三个寿命常数. 在237.7 nm激发下,得到2.1±0.1 ps和13.1±1.2 ps两个寿命常数. 所有寿命常数都归属为S₁态的振动态. 本文并对不同S₁振动态的弛豫机理进行了讨论.     

Role of the Medium in Radiationless Conversion of the Energy of the Excited S 1 State in Equilibrium Systems with Intramolecular Charge Transfer

Using the Onsager model, the effect of molecular orientation interactions in solutions on the rate constant of radiationless conversion of the energy of the excited S ₁ state has been calculated for equilibrium systems with intramolecular charge transfer. The rate constant of the radiationless conversion of energy S ₁ — X _n is represented as a function of the polarity of the medium f() = ( – 1)/(2 + 1), where is the permittivity of a solvent. The results obtained are compared with the Marcus theory and are also used to explain the well-known literature data on the influence of a solvent on the lifetime of the S ₁ state of some carotenoids.     

锂分子2~3π_g-a~3∑_u~+受激扩散带辐射线型的理论计算

本文利用由RKR方法计算得到的锂分子2~3∏_g态和a~3∑_u~+态(束缚部分)的势能曲线求解振动薛定谔方程,获得了2~3∏_9—a~3∑_u~+跃迁的F-C因子,自发辐射系数,进而计算了该跃迁的荧光强度和受激辐射带强度的光谱分布,其结果与实验测得的由双光子激发锂分子产生的受激扩散带辐射相吻合.     

Unified Solution of the Expected Maximum of a Discrete Time Random Walk and the Discrete Flux to a Spherical Trap

Two random-walk related problems which have been studied independently in the past, the expected maximum of a random walker in one dimension and the flux to a spherical trap of particles undergoing discrete jumps in three dimensions, are shown to be closely related to each other and are studied using a unified approach as a solution to a Wiener-Hopf problem. For the flux problem, this work shows that a constant c = 0.29795219 which appeared in the context of the boundary extrapolation length, and was previously found only numerically, can be derived analytically. The same constant enters in higher-order corrections to the expected-maximum asymptotics. As a byproduct, we also prove a new universal result in the context of the flux problem which is an analogue of the Sparre Andersen theorem proved in the context of the random walker's maximum.     

High-Resolution Study of the BaI AΠ Electronic State

Near-infrared and visible spectra of the A²Π–X²Σ⁺, C²Π_1/2–A²Π_1/2, C²Π_1/2–B²Σ⁺, and C²Π_1/2–X²Σ⁺ band systems of the BaI molecule were recorded by using Fourier transform spectroscopy (FTS). The spectra were produced from the chemiluminescent reaction Ba + I₂ and also by using laser-induced fluorescence (LIF) technique in which the laser sources were a Ti:sapphire single-mode laser, a dye single-mode laser, and a Kr⁺ multimode ion laser. Resolved rotational data, originating from 19 vibrational levels (0 ≤ v ≤ 5 and 7 ≤ v ≤ 19) of the A²Π state, 24 vibrational levels (0 ≤ v ≤ 18 and 20 ≤ v ≤ 24) of the X²Σ⁺ state, and 8 vibrational levels (1 ≤ v ≤ 2 and 9 ≤ v ≤ 14) of the C²Π state, were used in the final analysis. Previously recorded data for the B²Σ⁺–X²Σ⁺ and C²Π–X²Σ⁺ systems, taken from R. F. Gutterres, J. Vergès, and C. Amiot, J. Mol. Spectrosc. 196, 29–44 (1999) and from C. A. Leach, A. A. Tsekouras, and R. N. Zare, J. Mol. Spectrosc. 153, 59–72 (1992), were added to the present work data field. Accurate and improved molecular constants, for the X²Σ⁺, B²Σ⁺, A²Π, and C²Π states, were derived from a simultaneous treatment of the whole data set.     

Probing DNA Hybridization in Homogeneous Solution and at Interfaces via Measurement of the Intrinsic Fluorescence Decay Time of a Single Label

The hybridization of DNA oligomers including molecular beacons can be detected by measurement of either the decay time or the intensity of a single fluorescent label attached to the end of the respective oligonucleotide. The method works both in solution and solid phase and can distinguish between fully complementary and mismatch sequences as demonstrated for a 15-mer oligonucleotide and a 25-mer molecular beacon. The fluorescence lifetime method is advantageous in (a) requiring a single label (and therefore a single labeling step) only; and (b), being based on measurement of a self-referenced magnitude that is hardly affected by parameters such as fluctuations in light intensity that make measurement of intensity more prone to interferences.