90Mo电磁跃迁几率的测量

利用束流能量为116MeV的⁵⁹Co(³⁵Cl,2p2n)⁹⁰Mo反应布居⁹⁰Mo的高自旋态.用10台反康普顿HPGe探测器组成的探测阵列进行γγ符合测量.通过多普勒展宽峰的形状分析测定⁹⁰Mo高自旋态的寿命.在正宇称衰变系观察到增强的M1跃迁,推断I=13以上是扁椭形变.负宇称高自旋态具有大的B(E2)值,并随自旋增大而起伏变化.正、负宇称态之间的跃迁显示增大的E1跃迁,似有八极关联的可能.但是,⁹⁰Mo并不处在理论预言的存在八极形变的核区内.     

GaN激子跃迁的时间分辨光谱学研究

用时间分辨光谱学方法研究低压有机金属化学汽相沉积生长的ＧａＮ中自由，束缚激子（ＢＸ）的跃迁，讨论了这些跃迁的光致发光谱，复合寿命及其与温度的关系，给出了中性施主束缚激子和自由激子（ＦＸ）的辐射复合寿命分别为０．１２ｎｓ和０．４ｎｓ。     

Quantum chromodynamics studies at LEP2

Several studies have been made to the hadronic final states in e ⁺ e ⁻ collisions at LEP. Studies of the annihilation process at LEP2 have given rise to results on jet rate, event shape, heavy flavour production, inclusive momentum spectra, Bose-Einstein correlation and colour reconnection effects. Event shape studies have given rise to accurate determination of the strong coupling constant α _s using O (α _s ² ) with resummed leading and next-to-leading log calculation and also with power law corrections. Studies of 2-photon processes have yielded results on γγ cross-section, heavy flavour production, photon structure function and γ*γ* scattering.     

Comparative analysis of the effects of internal lasing oscillation and external light injection on semiconductor optical amplifier performance

One of the key differences of a semiconductor optical amplifier (SOA) with internal lasing oscillation (ILO) from a SOA with external light injection (ELI) lies in a carrier-sharing mechanism. Since the internal lasing mode shares the same pool of carriers with the signals, the carriers (or photons) withdrawn from the circulating laser mode speed up the gain recovery. On the other hand, the external light injected into the SOA shortens the carrier recovery time through optical pumping without any carrier sharing involved. To find out a better scheme, we have made a comparative investigation on the effects of the ILO and ELI on the SOA performance. It turns out by way of simulation that the ELI scheme provides faster gain recovery, shorter carrier lifetime, and higher saturation power when the external injection power is higher than the internal lasing power. The performance enhancement is not so pronounced with the carrier-sharing mechanism, as the internal lasing mode itself gives rise to severe longitudinal spatial hole burning (LSHB). Nevertheless, the ILO scheme is preferable for linear-amplification applications. We also examine the use of the ELI for low-crosstalk optical amplifiers. It is found that the ELI scheme does not bring in a very strong resonance peak in the crosstalk, which appears in a SOA with ILO due to relaxation oscillations of the lasing mode. In comparison to the ILO in SOAs, the ELI into SOAs is likely to leave more optical gain for multi-channel amplification without any sacrifice on the crosstalk.     

Understanding the influence of nanoenvironment on luminescence of rare-earth ions

This paper presents an overview of the recent results on upconversion and photoluminescence of rare-earth ions in nanoenvironments. The role of the rare-earth ion concentration, crystal size and crystal phase on the up and downconversion emission of rare-earth ions in oxide nanocrystals and their underlying mechanisms are discussed. It is also found that the luminescence lifetime of the excited state rare-earth ions is sensitive to the particle crystalline phase and size. The analysis suggests that the modifications of radiative and nonradiative relaxation mechanisms are due to local symmetry structure of the host lattice and crystal size respectively     

负碳离子（2s^22p^3）和（2s^12p^4）的光离解

电子关联效应在负离子中的作用相当重要，本文讨论了负碳离子（２ｓ＾２２ｐ＾２）和（２ｓ＾１２ｐ＾４）的能级结构、光谱跃迁、寿命和光离解通道等。碳负离子（１ｓ＾２２ｓ＾１ｐ＾４）的双重态比四重态稳定，（２ｓ＾２２ｐ＾４）和（２ｓ＾１２ｐ＾４）之间各辐射谱线波长位于超紫外区域的上限附近，其光谱强度很大的波长有６条，为研制Ｘ射线激光提供了有利的工作物质。     

Calcium imaging using fluorescence lifetimes and long-wavelength probes

We describe imaging of calcium concentrations using the long-wavelength Ca²⁺ indicators, Calcium Green, Orange, and Crimson. The lifetimes of these probes were measured using the frequency-domain method and were found to increase from 50% to severalfold in response to calcium. The two-dimensional images of the calcium concentration were obtained using a new apparatus for fluorescence lifetime imaging (FLIM). We also describe procedures to correct for the position-dependent frequency response of the gain-modulated image intensifier used in the FLIM apparatus. Importantly, the FLIM method does not require the probe to display shifts in the excitation or emission spectra. Using the FLIM method, calcium imaging is possible using probes which display changes in lifetime in response to calcium. Consequently, calcium imaging is possible with excitation wavelengths ranging from 488 to as long as 620 nm, where autofluorescence and/or photochemical damage is minimal. These probes are also suitable for calcium measurements of single cells using lifetime-based flow cytometry.     

伴随着分子内电荷分离的分子内转动模型的时间分辨荧光光谱研究

本文采用时间分辨荧光光谱方法,考查了两种7-胺基香豆类素衍生物分子在不同溶剂中的荧光辐射弛豫过程,研究了环境因素对伴随着分子内电荷转移的分子内转动激发态(TICT)弛豫过程的影响。结果说明TICT态是非刚性香豆素分子激发态无辐射弛豫路径之一,这一过程受到环境介质的极性、粘度和温度的影响。并指出了在考虑粘度影响时,须对DSE理论进行修正,同时提出了TICT态存在位垒的观点。     

环氧树脂-胺类固化体系微结构的正电子湮没研究

采用正电子漂没寿命谱（PALS）研究固化剂的种类有含量对环氧树脂基体自由体积特性、力学性能和密度的影响，实验结果表现：固化剂的含量与理论值接近，固化产物的自由体积半径越小，密度越高，力学性能越好，固化剂中的氨基对环氧基发生交联作用的程度，直接影响了固化产物的密度及力学性能。