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801.
Xiaofang Wang Pingbo Xie Fuli Zhao Hezhou Wang Yanmin Wang 《Particuology》2009,7(6):496-500
Time-integrated photoluminescence (PL) spectra between 1.2 and 2.25 eV of ZnO nanoparticles were observed at ambient temperatures when they were excited by a picosecond (ps) laser pulse at a low photon energy of 2.33 eV/532 rim, to show clear red shift when the excitation intensiW increased. Gaussian analysis shows that the red shift is due to increase of the relative magnitudes of the Gaussian combination in the low energy region. Temporal evolution of the dominant emissions exhibited a similar double-exponential decay process, in which the respective two distinct decay durations of 189 ps at the corresponding amplitude of 82% and 2081 ps at 18% were identified. Speculation based on the surfacestate emission due to the large surface-to-volume ratio of nanoscale materials is used to explain the phenomena. 相似文献
802.
中微子的量是很稀少的,它的质量和相互作用也是很小的,但在太阳内部,作为核聚变反应的副产品,它的数量却是很巨大的。由此可见,中微子是经常出现于核反应与宇宙射线簇射中,过去安置于地下的陆地探测器曾给出过各种中微子的记录,现在由于掌握了测定地球内部辐射衰变中电子反中微子的数量,从而开辟了中微子物理的一个新纪元, 相似文献
803.
结合ψ(2S)扫描实验中衰变宽度测量的特点,介绍了确定积分亮度的叠代方法与确定衰变宽度误差的抽样方法.这两种方法既简单又精确可靠 相似文献
804.
使用壳模型系统地研究了丰中子氮同位素的β ̄衰变,并对其衰变子核18,19,20,210的能级结构性质给出理论计算,所得结果与实验符合较好.研究了18,19,20N核的Gamow-Teller允许型β ̄衰变的特性,对与近期实验观测不一致之处进行了讨论和分析.预言了21N的β ̄衰变及其子核高激发态的能级结构性质.这些计算将对氮同位素的实验研究很有帮助. 相似文献
805.
806.
In this article, we assume that the (0^+,1^+) strange-bottom mesons are the conventional bs mesons, and calculate the electromagnetic coupling constants d, g1, g2, and g3 using the light-cone QGD sum rules. Then we study the radiative decays Bs0→Bs^*γ, Bs1→Bsγ, Bs1→Bs^*γ, and Bs1→Bs0γ, and observe that the widths are rather narrow. We can search for the (0^+, 1^+) strange-bottom mesons in the invariant Bsπ^0 and Bs^*π^0 mass distributions in the strong decays or in the invariant Bs^*γ, and Bsγ mass distributions in the radiative decays. 相似文献
807.
The nonlinear photoluminescence (PL) including second-harmonic generation (SHG) and the multiphoton luminescence (MPL) around 385 nm and 530 nm from ZnO nanobelts are investigated by using near-infrared excitations. The excitation wavelength dependence of MPL intensity reveals resonant energy transfer from SHG to MPL near the band gap excitation. The lifetime measurement of the MPL shows a much slower decay process of the defect emission, which results from the generation and recombination of both donors and acceptors on the disordered surface of the ZnO nanobelts. 相似文献
808.
The topcolor-assisted technicolor (TC2) model predicts the existence of the top-pions and the CP-even top-Higgs with large flavor-changing couplings to the top quark, which at tree-level can mediate the top quark three-body decay t → cb-↑b. We study this decay, show the dependence of the decay rate on the relevant TC2 parameters and compare the results with the predictions in the minimal supersymmetric model. We find that the decay rate in the TC2 model is much larger than that in the minimal supersymmetric model if the new particles are not too heavy. However, in consideration of the ODF and the LEP experiment limits, the top-pion mass is greater than 340 GeV in a more realistic parameter space, so the decay width of the channel t → cb-↑b intermediated by top-pions will be depressed greatly and difficult to be detected at the future collider. Thus, to observe this channel at the future collider, considering the top-higgs contribution may be the possible way when the masses of the top-pions and the top-higgs are not degenerate. 相似文献
809.
运用推广的液滴模型(GLDM)确定了超重核294118和291116及其α衰变链上各核素的衰变势垒, 采用量子力学中的WKB方法计算α衰变中的势垒穿透几率, 对该链上各原子核的α衰变半衰期进行了研究。 此外, 还利用Royer公式对该链上各原子核的α衰变半衰期进行了计算。 结果表明, GLDM 考虑亲和能与Royer公式给出的α衰变半衰期与超重核区的实验值符合很好, 验证了GLDM和Royer公式在超重核区的适用性,可以用来预测超重核的半衰期。 最后, 预言了Z=118 和116 同位素链上各核素的半衰期, 结果表明, 在Z=118和116中存在α衰变长寿命同位素, 这需要实验上的检验。The α decay potential barrier of the newly synthesized superheavy nuclei starting from 294118 and 291116 have been determined and their half lives have been studied with the Generalized Liquid Drop Model(GLDM) connected with WKB approximation and Royer’s formulae.The α decay half lives of the nuclei belonging to the superheavy nuclei starting from 294118 and 291116 have been calculated.The calculated results are in agreement with the experimental data, which show that the α decay half lives of superheavy nuclei with the GLDM and Royer’s formulae can be applied in the studying on superheavy nuclei successfully.Finally, the half lives of Z=118 and 116 isotopes have been predicted, and the results suggest there may be some long lived superheavy nuclei for α decay in those isotopes. 相似文献
810.
北京谱仪(BES)已收集了2.5×107个J/ψ事例,并计划增加到108—109个.本文综述近年来在BES上寻找新物理的研究,包括在J/ψ衰变过程中探测新的味改变中性流,CP破坏和轻子味破坏. 相似文献