21世纪的光学和光电子学讲座 第二讲 硅基发光材料和器件研究

硅基发光材料和器件是实现光电子集成的关键。文章评述了目前取得较大进展的几种主要硅基发光材料和器件的研究，包括掺饵硅，多孔硅，纳米硅以及Si/SiO_2等超晶格结构材料。展望了这些不同硅基发光材料作为发光器件和在光电集成中的发展前景。

辐射固化面向——21世纪的绿色工业的新技术

概述了辐射固化新技术的发展过程 ,简述了紫外光固化和电子束固化机理、所需设备和涂层的原材料 .与常规固化方法比较 ,辐射固化具有低能耗、高效率和无污染的优点 ,是面向 2 1世纪的绿色工业的新技术 .

Experimental study of the beta-delayed neutron decay of N-21

The first spectroscopic study for the beta decay of N-21 is carried out based on beta-n, beta-gamma, and beta-n-gamma coincidence measurements. The neutron-rich N-21 nuclei are produced by the fragmentation of the E/A=68.8 MeV Mg-26 primary beam on a thick Be-9 target and are implanted into a thin plastic scintillator that also plays the role of beta detector. The time of flight of the emitted neutrons following the beta decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the beta-delayed gamma rays. Thirteen new beta-delayed neutron groups are observed with a total branching ratio of 90.5 +/- 4.2%. The half-life for the beta decay of N-21 is determined to be 82.9 +/- 7.5 ms. The level scheme of O-21 is deduced up to about 9 MeV excitation energy. The experimental results for the beta decay of N-21 are compared to the shell-model calculations.

Investigation of excited states in Mg-22 via resonant elastic scattering of Na-21+p and its astrophysical implications

The excited states in 22Mg have been investigated by the resonant elastic scattering of 21Na + p. A 4.0 MeV/nucleon 21Na beam was separated by the Center for Nuclear Study (CNS) radioactive ion beam separator (CRIB) and then used to bombard a thick (CH2)n target. The energy spectra of recoiled protons were measured at scattering angles of θc.m. ≈ 172◦ , 146◦, and 134◦, respectively. A wide energy-range of excitation function in 22Mg (up to Ex ∼ 8.9 MeV) was obtained simultaneously with a thick-target method, and a state at 7.06 MeV was newly observed. The resonant parameters were deduced from an R-matrix analysis of the center-of-mass (c.m.) differential cross-section data with a SAMMY-M6-BETA code. The astrophysical resonant reaction rate for the 18Ne(α,p)21Na reactionwas recalculated based on the present parameters. Generally speaking, the present rates are much smaller than the previous ones.

The beta decay of N-21

The beta-delayed neutron and gamma energy spectra taken from the decay of neutron-rich nucleus N-21 were measured by using the beta - gamma and beta - n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98 MeV and with a total branching ratio of 88.7 +/- 4.2% were observed and presented. One gamma transition with an energy of 1222 keV emitted from the excited state of O-21, and four gamma transitions with energies of 1674, 2397, 2780, and 3175 keV emitted from the excited states of O-20 were identified in the 3 decay chain of N-21. The beta decay half-life for N-21 is determined to be 82.9 +/- 1.9 ms. The uncertainty of half-life is much smaller than the previous result.