一道数列趣题的解析

2009年湖南理科第15题是一道背景新颖、内涵丰富,具有一定探究价值的“好题”,是训练学生合情推理能力的良好素材．本文给出该题的四种解法供大家参考．     

低能Ar9+离子与Na原子碰撞反应中的多电子转移过程

利用近代物理研究所新建的原子物理实验平台,采用位置灵敏探测和散射离子-反冲离子飞行时间符合技术,研究了180 keV的Ar9+离子与Na原子碰撞中的多电子转移过程,对实验结果做了分析和简单的讨论,并同修正后的分子库仑过垒模型结果进行了比较.     

高功率Nd∶YVO4/KTP腔内倍频晶体温度分布的半解析热分析

非线性晶体KTP采用Ⅱ类相位匹配腔内倍频时,不仅要求晶体满足基频光的偏振匹配条件,而且所选用的晶体要求符合λ/2波片的条件,才能使晶体的谐波转换效率达到最佳.由于倍频晶体吸收基频光能量引起晶体内部非均匀温升,改变晶体内部各点的折射率,也会使晶体产生不应有的热形变,破坏晶体初始的位相匹配条件,严重影响输出激光的品质和倍频效率.减弱、改善这种情况的关键是准确得出在实际工作条件下晶体内部温度场.利用半解析热分析方法得出了KTP晶体内部温度场的计算方法,分析了各种热参量变化对KTP晶体内部温度场的影响.得出的结果具有一定的普适性,可以应用到具有轴对称形式内热源的其它热模型温度场的计算分析中,对连续波腔内倍频激光系统的设计将起到指导作用.     

掺铒重金属氧氟硅铋酸盐玻璃的光谱性质

研究了重金属氧氟硅铋酸盐玻璃 (50-x)SiO2 xBi2O3 50PbF2(x=0, 3, 5, 8, 10, 13, 15 mol%)中Er3+离子的吸收光谱、荧光光谱、荧光半高宽、荧光 寿命和热稳定性能.应用Judd Ofelt理论计算了玻璃的强度参数Ωt(t=2,4,6)，应用 McCumber计算了能级4I13/2→4I15/2跃迁的受激发射截面. 结果发现荧光半高宽与Ω6有较大联系，Ω6越大，荧光半高宽越宽.对Er3+ 关键词： 重金属氧氟硅铋酸盐玻璃 光谱性质 Er3+离子 Judd Ofelt参数     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime. The higher harmonic cavity of Shanghai Synchrotron Radiation Facility (SSRF) is a 1.5GHz passive superconducting cavity. Its higher order modes (HOM) are extracted by a ferrite HOM damper out of the cryostat. Multi-cell cavity is chosen concerning the voltage. The harmonic cavity dynamics, beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.     

纳秒激光诱导C60分子碎裂中轻碎片离子C+n(n《30)的产生机理研究

采用飞行时间质谱计测量了纳秒激光诱导C60分子碎裂中轻碎片离子C n(n≤11)的初始平均动能,结果显示轻碎片离子具有相同的初始平均动能(约为0.34 eV),并且该动能在一定范围内不随激光通量的变化而明显改变.结合前人的实验结果,对纳秒激光诱导C60分子碎裂中轻碎片离子C n(n<30)的主要产生模式作了新的阐述,即C60分子级联发射15个C2分子和一个电子形成自身不稳定的C 30离子,在皮秒时间尺度内C 30离子的笼形结构塌陷,进而轻碎片离子产生.     

Design of Two-Dimensional Photonic Crystal Edge Emitting Laser for Photonic Integrated Circuits

An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of air-holes, and a waveguide. In the cavity, laser resonance in the inner structure benefits from not only the anomalous dispersion characteristic of the first band-edge at the M point in the first Brillouin-zone but also zero photon states in the outer structure. A line defect waveguide is introduced in the outer structure for extracting photons from the inner cavity. Three-dimensional finite-difference time-domain simulations apparently show the in-plane laser output from the waveguide. The microcavity has an effective mode volume of about 3.2（λ/nslab）^3 for oscillation mode and the quality factor of the device including line defect waveguide is estimated to be as high as 1300.     

Theoretical Investigation on Excitation,Ionization and Capture in H（1s, 2s） ＋ H（1s, 2s） Collisions

Cross sections of electron-loss in H（1s）＋ H（1s） collisions and total collisional destruction of H（2s） in H（1s） 4- H（2s） collisions are calculatted by four-body classical-trajectory Monte Caylo （CTMC） method and compared with previous theoretical and experimental data over the energy range of 4-100 keV. For the former a good agreement is obtained within different four-body CTMC calculations, and for the incident energy Ep 〉 10 keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approx- imation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H（2p）, single- and double-ionization and H- formation in H（2s）＋H（2s） collisions are calculated in the energy range of 4-100 keV for the first time, and compared with those in H（1s）＋H（1s） and H（1s）＋U（2s） collisions.     

Dependence of Crystal Quality and β Value on Synthesis Temperature in Growing Gem Diamond Crystals

High quality Ib gem diamond single crystals were synthesized in cubic anvil high-pressure apparatus （SPD- 6 × 1200） under 5.4GPa and 1230℃-1280℃. The （100） face of seed crystal was used as growth face, and Ni70Mn25Co5 alloy was used as solvent/catalyst. The dependence of crystal quality andβ value （the ratio of height to diameter of diamond crystal） on synthesis temperature was studied. When the synthesis temperature is between 1230℃ and 1280℃, theβ value of the synthetic high-quality gem diamond crystals is between 0.4 and 0.6. The results show that when theβ value is between 0.4 and O. 45, the synthetic diamonds are sheet-shape crystals; however, when theβ value is between 0.45 and 0.6, the synthetic diamonds are tower-shape crystals. In addition, when theβ value is less than 0.4, skeleton crystals will appear. When theβ value is more than 0.6, most of the synthetic diamond crystals are inferior crystals.     

籽晶{100}面形状对高温高压合成金刚石大单晶的影响

选用不同形状的{100}金刚石籽晶面,以NiMnCo合金为触媒,利用温度梯度法在压力为5.5 GPa、温度为1260～1300℃的条件下,合成Ib型金刚石大单晶。通过光学显微镜和电子显微镜对晶体的形貌进行表征。研究发现,将合成籽晶的{100}晶面切割成不同形状,只会令晶体的长宽比发生改变,晶体并不会因籽晶形状的改变而偏离{100}晶体的正常形貌。晶体的合成质量受到籽晶长宽比的影响:在籽晶长宽比较小的情况下,晶体的合成质量能够得到保证;但当籽晶长宽比过大时,合成晶体的下表面出现较多缺陷。关于籽晶形状对晶体生长情况影响的研究,揭示了籽晶形状与合成晶体形貌之间的关系,有利于更深入理解晶体的生长过程和外延生长机理,对于今后合成不同形貌的金刚石具有借鉴意义。同时此项研究有助于扩大籽晶的选取范围,降低籽晶的选择难度,提升工业级金刚石的利用率,为合成金刚石大单晶的籽晶选取提供了技术支持。