Strengthened Hyper-Raman Lines with the Coherent Superposition State

High-order harmonic generations from a one-dimensional Coulomb potential atom are calculated with the initial state prepared as a coherent superposition between its ground and first excited states. When the energy difference of the two states is small, we can choose proper laser pulse such that the first excited state can be excited only to other bound states instead of being ionized. We show that only the hyper-Raman lines are observable instead of the harmonics. The energy difference of the ground and the first excited state can be deduced from the highest peak of the hyper-Raman lines. We further show that the similar results can be obtained by using a combination of two laser pulses with different frequencies interacting with the atom initially at the ground state.     

不同气体环境下532nm激光诱导硅表面形貌的研究

研究了在不同气体环境下,利用532nmNd：YAG纳秒脉冲激光累积辐照单晶硅表面形成的微结构,结果表明,在其他条件相同,背景气体不同的情况下,背景气体对硅表面形貌的形成起着重要的作用。具体分析了真空、N2和SF6 3种环境气氛下形成的微结构,结果显示,在sF6中形成的锥形微结构的数密度比在N2和真空中的大,并且锥形具有更大的纵横比;在N2、真空和sF6中形成的微结构尺寸依次减小。sF6气氛下,激光辅助化学刻蚀的效率比在真空和N2气氛中的高。另外,辐照区域边缘有波纹微结构形成,分析认为,该微结构的形成是由表面张力波的冷却导致的。     

斜入射激光等离子体堵口时空特性研究

在“星光II”上首次利用X光12分幅相机(XFC)成功地观测到了1.053 μm激光以45°方向斜入射孔靶和半腔靶等离子体堵口的时间和二维空间图象,获得了等离子体堵口速度,同时通过一维模型给出了斜入射条件下的等离子体堵口速度。实验结果表明：相同参数条件下半腔靶与孔靶相比,等离子体喷射速度高约15%。一维模型给出的等离子体喷射速度与XFC测出的等离子体喷射速度在实验误差范围内是一致的。     

叶片扩压器进口安装角对离心压缩机性能影响的数值与实验研究

对不同扩压器进口安装角下离心压缩机的性能进行了实验研究,并详细计算分析了相应的流场分布。分析表明, 不同的进口安装角对压缩机的流动有较大的影响,压缩机的性能曲线也有不同程度的左右偏移;进口处较大的正冲角和负冲角均会在扩压器叶片表面出现大尺度的分离涡团;在给定的流量工况下,应存在一个最佳的进口安装角,使得扩压器效率最高;设计工况下,最高效率所对应的冲角并非为零。     

分级进风燃烧室内高温气固两相流动的PDA测量

本文建立了分级进风燃烧室高温气固两相流动的实验装置。利用三维激光粒子动态分析仪(PDA),测量了燃烧室内有气相燃烧的高温气固流动的两相瞬时速度场。得到了平均轴向与切向速度、轴向与切向脉动速度均方根值和轴向-切向脉动速度关联量的分布。     

基于上海激光电子γ源的天体核合成关键反应12C(α,γ)16O的反应率研究

正在研制的上海激光电子γ源是MeV量级的高品质γ光束线站，基于该装置可以开展一系列核天体物理实验, 从而更准确的确定各天体核合成反应的反应率. 本文研究了天体核合成中的关键反应¹²C(α,γ)¹⁶O的反应率. 根据多组实验和理论截面数据分别计算了反应率, 并给出了这些反应率计算结果的平均值和统计误差. 根据该结果拟合了理论反应率的解析形式, 确定了新的参数. 进而给出俘获反应¹²C(α,γ)¹⁶O在He燃烧环境下的反应率和误差, 并讨论了电子屏蔽效应对天体反应率的修正.     

等离子体屏蔽效应对原子能级和振子强度的影响

利用Debye模型,研究了等离子体屏蔽效应对热等离子体中原子能级和振子强度的影响.通过在MCDF模型中引入等离子体屏蔽效应,计算了MnXXII-BrXXII等11个类Be离子在等离子体环境下2s²—［2s_1/2,2p_1/2］₁和2s²—［2s_1/2,2p_3/2］₁跃迁的能级和振子强度.计算结果表明,等离子体屏蔽效应使得类Be离子2s²—［2s_1/2,2p_1/2］₁跃迁的激发能量增大,从而导致谱线蓝移现象;并且随着屏蔽效应的不断增强,蓝移的程度会逐渐加大.屏蔽效应对于2s²—［2s_1/2,2p_3/2］₁跃迁的振子强度也有类似的影响. 关键词： Debye 等离子体屏蔽 跃迁能级 振子强度     

Theoretical simulations of emission spectra of Fe^7＋ and Fe^＋8

The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http：//www.astrnomy.csdb.cn/EIE/.     

Improved data analysis method of single-molecule experiments based on probability optimization

To extract the dynamic parameters from single molecule manipulation experiments, usually lots of data at different forces need to be recorded. But the measuring time of a single molecule is limited due to breakage of the tether or degradation of the molecule. Here we propose a data analysis method based on probability maximization of the recorded time trace to extract the dynamic parameters from a single measurement. The feasibility of this method was verified by dealing with the simulation data of a two-state system. We also applied this method to estimate the parameters of DNA hairpin folding and unfolding dynamics measured by a magnetic tweezers experiment.     

利用球模型计算的能量在0.1—10.0电子伏的电子被CH_4和SiH_4分子弹性散射的截面

在Born—Oppenheimer近似下。对分子体系中的电子运动哈密顿中势能项中的原子核部分以C原子和Si原子为中心做多极展开,保留展开式中的第一项,就得到一个CH_4和SiH_3分子的球对称模型,在此模型下,用X_α方法并考虑到自相互作用修正(SIC),计算了CH_4和SiH_4的电子波函数,电子密度分布和分子总能量,得到的分子总能量分别为—39.50和—290.22 Hartree。接近—39.72和—290.97的Hartree—Fock结果。利用我们求出的电子波函数,用分波法计算了能量在0.05—10.0eV的电子被CH_4和SiH_4弹性散射的总截面和各分波截面,在计算中交换势取Hara的自由电子气模型,相关极化势则采用近程相关势和远程极化势相连接的方法。计算结果除R—T极小值偏低外,R—T效应的位置及整个截面和新的实验值吻合的很好。