共查询到20条相似文献,搜索用时 52 毫秒
1.
采用时间分辨光谱技术(时间分辨率为0.15ns)系统地研究了两种典型香豆素激光染料(C311和 C102)的荧光衰变过程的溶剂效应。测量结果表明,这类香豆素激光染料的荧光寿命溶剂效应具有“反常”特性,即随着溶剂极性的增大其荧光寿命加大。基于香豆素激光染料处于激发态时发生电荷转移而使分子偶极矩有很大增加这一事实,作者认为处于激发态的染料分子将使溶剂分子进行重新排列,即发生了溶剂“结构化”过程,极性越大,“结构化”程度越高。这种“结构化”效应将阻止染料分子弛豫到基态,从而加大了荧光寿命。但对具有可能转动端基(CH_3)_2N— 相似文献
2.
3.
GaAs载流子的超快动力学特性 总被引:2,自引:2,他引:0
利用飞秒瞬态反射谱,研究了GaAs的载流子的超快动力学特性。根据实验结果,分析了弛豫过程,并通过计算,分析了自由载流子和晶格温度效应对弛预过程的影响,并给出了定量计算结果,分别为-7.33x10~(-4),0.85×10~(-4)。 相似文献
4.
5.
6.
7.
8.
近年来超快过程研究进展迅速,现分辨率已达到1fs,激发态的寿命是纳秒,因此有可能用超快过程方法研究激发态的响应过程和动力学演化激发态具有基态所不具有的新的物理性质,因此近年来光激发引起的新现象研究已成为物理、化学和材料等交叉学科领域中的一个新的生长点. 本工作用含时薛定谔方程和分子动力学方法研究了在外加电场作用下,具有一个额外电子和空穴的聚合物链(即自陷束缚单激子态)在吸收一个光子,变成具有两个额外电子和空穴的聚合物链(即自陷束缚双激子态)时,聚合物链中键结构和电荷密度分布的动力学演化过程.发现… 相似文献
9.
10.
采用时间相关单光子计数技术测量了DCM在几种典型的极性溶剂(乙醇、二甲苯亚砜和丙烯碳酸酯)中的荧光衰变过程。所得的荧光衰变曲线和被测的荧光波长无关,并可用单指数衰变函数描述。基于对双重荧光发光动力学的一般分析指出:DCM在极性溶剂中的双重荧光仍遵守单指数衰变动力学规律的原因,是由于产生荧光的两种DCM激发态之间可以快速地互相转化,而且转化速率远远超过各激发态的辐射和无辐射跃迁到基态的速率所致。 相似文献
11.
The article describes a model representation of radar probing data in form of a mixture of background and target samples, which is the sum of two random variables with very different parameters. For model development we research the behavior of the central moments of the distribution mix without assuming the distribution law form. An example it is described the detection of the signal at the output of compression system of chirp ionosonde. 相似文献
12.
By means of exact conformal mapping method we have defined character of dependence of squares amounts of angular part of film
element on angled part dimension. We propose relations, approximating obtained dependence. Calculation results and experimental
researches of large-scale models are represented. 相似文献
13.
14.
15.
解决IP网QoS问题是目前通信领域的研究热点之一.虽然研究已经取得了一定的进展,但人们对于IP 网QoS本身的含义及相关的问题还有着不同的理解.本文将从IP网QoS的定义入手讨论相关的一些问题以及解决IP网QoS问题所做的各种努力. 相似文献
16.
《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1968,56(6):1024-1032
Assuming that visual responses are due to the action of particles on the membrane of the visual cells, the stochastic variability of the response should be a function of the number of particles producing it. Quantitative predictions can be made with the aid of a model proposed in previous articles. It is found that responses produced in visual cells of Limulus by absorption of a single photon have the stochastic properties which would be expected if the response to one photon were brought about by 25 particles. It is concluded from this that the processes leading to visual responses produce multiplication of particles. The effects of temperature and of metabolic poisons suggest that these processes are of chemical nature. 相似文献
17.
Moshrefzadeh R.S. Radcliffe M.D. Lee T.C. Mohapatra S.K. 《Lightwave Technology, Journal of》1992,10(4):420-425
The temperature dependence of refractive index of polymer films was determined for a number of slab waveguides by a grating coupling method. This dependence was examined as a function of parameters such as molecular weight and glass transition temperature of the polymer. Temperature-induced changes in N TE-N TM , N being the effective index, were studied systematically for different slab waveguide compositions. It is shown that with proper device design and choice of polymeric materials, thermal effects can be reduced 相似文献
18.
The approaches to prepare a uniform and unified scientific terminology of chemical carcinogenesis are presented. The main definitions proposed (carcinogen, initiation, promotion, mutagen, multistage carcinogenesis, anti-carcinogen, cocarcinogen, carcinogenic risk, etc.) are based on the current state of comprehending mechanisms of the action of chemical carcinogens. 相似文献
19.
上市公司为了增强市场竞争力,不断扩大生产规模,追求规模经济,但是由于我国较低生产力水平、政府干预、体制等原因,上市公司的规模经济效果并不明显。同时,20世纪90年代以来,科学技术的日益发展,改变了企业发展的外部环境和条件,使得规模经济的实现方式发生了新的变化。在信息化时代下,规模经济理论需要进一步创新和拓展,企业按照新形势来选择合适的经济规模。 相似文献