等离子体X射线吸收谱及发射谱研究

报道计算高温高密等离子体吸收谱和发射谱（光学薄）的理论方法;该方法基于相对论原子理论,可以计算任何单元素以及多元素等离子体的谱分辨X射线吸收谱和发射谱（光学薄）;应用了量子亏损理论,可以减少计算量。利用该方法计算金等离子体LTE吸收谱,计算结果与实验符合良好。本文还对金等离子体LTE的光学薄发射谱进行了研究, 这将有利于对实验进行进一步的诊断分析。该理论计算方法还可提供等离子体内各电离度能级布居等重要物理参数。因此经“标准实验”检验的该理论计算方法将是提供ICF“精密”物理辐射参数的重要基础。     

激光等离子体非平衡X射线发射谱理论研究

在平均离子模型的基础上,发展了一个计算离子组态概率分布的有效方法,称为统计方法.根据激光靶耦合程序模拟给出腔靶等离子体状态条件,研究1.06μm激光金等离子体的非平衡离子组态分布和X射线发射谱特性.得到与实验谱相同的能带范围,并得出在激光等离子体中多电子同时处于激发态的离子组态对X射线发射的贡献不能忽略的结论. 关键词：     

激光等离子体类氖GeX射线吸收谱研究

在国际上首次进行了空间分辨的激光等离子体类氖ＧｃＸ射线吸收谱研究．实验在高功率激光物理联合实验室的神光六路装置上进行，采用新颖的“点投影（ｐｏｉｎｔｐｒｏｊｅｃｔｉｏｎ）”吸收谱方案，研究了激光脉冲峰值以后２００ｐｓ时刻Ｇｅ等离子体中类氖离子密度的空间分布特性（空间分辨约２４μｍ），结果获得了类氖Ｇｅ２ｐ－３ｄ的共振吸收谐信号。实验结果同国内一维流体力学ＪＢ１９编码的模拟结果进行了比较。     

预脉冲激光对线状等离子体X射线发射特性的影响

报道了能量比为１：１０、间隔为２００ｐｓ、脉冲宽度为１２０ｐｓ的双脉冲激光驱动线状等离子体的Ｘ射线发射特性。通过与单脉冲驱动情况比较，获得了预脉冲作用下，等离子体轴向辐射增强的空间分布特性。并针对若干重要的辐射跃迁的增强情况，讨论了它们各自的物理原因。     

结构研究的新方法X射线吸收精细结构谱（XAFS）

1988年底,北京正负电子对撞机一次对撞成功的喜讯,使我们受到极大的鼓舞。因为它不仅显示了我国的科技实力和水平,而且为我国的高能物理、同步辐射及其应用奠定了良好的实验基础。同步辐射是一种强辐射源。它具有强度高、亮度大、波段覆盖范围宽、无杂质辐射线以及具有时间分辨性等许多优点,因此,     

高度电离的锗激光等离子体X射线谱的辨认

本文结合理论计算得到的锗类钠、类氖、类氟、类氧离子的振子强度,对平面晶体谱仪拍摄的锗激光等离子体X射线谱,波长在6～10(?)范围内的40多条谱线进行了分类辨认.     

高温铝等离子体X光发射谱实验

 在神光-Ⅱ高功率激光装置上,以束匀滑的第九路钕玻璃二倍频激光均匀辐照薄层铝埋点靶,通过激光烧蚀作用产生较均匀的铝高温等离子体,用平面晶体谱仪在靶面前向和切向同时测量了X光发射谱信号,并将前向发射谱进行了定量化还原处理。利用辐射流体力学程序MULTI-1D首先对等离子体状态进行了模拟计算,然后采用基于碰撞辐射模型的光谱程序对该状态下的光谱开展了计算,并将实验测量光谱与理论计算光谱进行了比较和分析,符合得较好。     

合成金刚石中金属Ni结构形态的扩展X射线吸收谱研究

用荧光扩展X射线吸收谱(EXAFS)方法测量了人工合成金刚石中金属熔媒Ni的结构形态。Ni呈现出面心立方结构,与纯金属Ni相似。从Ni原子周围C原子的配位和Ni-Ni原子间距的增大,说明有C原子溶解于Ni中,估算出的溶解度为9at%,大大超过常压下Ni中C原子的溶解度极限2.7at%。金刚石中Ni原子近邻配位数比纯金属状态Ni中小。这表明Ni以微粒形式分布于金刚石中,推算出这些微粒尺度约为20?。 关键词：     

Uranium oxides investigated by X-ray absorption and emission spectroscopies

X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO₂, U₃O₈ and UO₃ are presented. The spectral shapes of the O Kα X-ray emission spectra of UO₃ exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO₂ and U₃O₈. This energy dependence is attributed to a significant difference in the oxygen-uranium hybridization between two different sites in the crystal structure of UO₃. The spectral shapes of UO₂ and U₃O₈ are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.     

1.06μm激光等离子体软X射线辐射及对原子序数的依赖

详细地研究了1.06μm激光等离子体X光的辐射特性;分析了不同谱带发射强度对激光能量的依赖关系,并给出了K、L、M、N、O谱带发射强度对原子序数的依赖关系.     

激光等离子体软X射线辐射能谱时间分辨测量研究

利用(国内最近研制成功的)带聚酰亚胺膜底衬的金透射光栅与软X射线条纹相机相配合,(在LF11~#激光装置上)使用波长为0.53μm的激光打靶,测量了平面Au靶软X射线时间分辨能谱。测量结果观察到了金等离子体的O带辐射强度随时间增加的现象。文章计算了光栅的衍射效率,并讨论了影响测量谱的几个关键因素。     

Z箍缩等离子体K壳层X射线自辐射单色成像

采用针孔配接对数螺线柱面晶体方案,研制了一种小型、靶室内置X射线单色成像器,用于获取Z箍缩等离子体K壳层自辐射单色图像。在阳加速器上对该成像器进行了测试,成功地获取了铝丝阵负载Z箍缩等离子体K壳层自辐射的类氢线与类氦线单色图像。实验结果表明:该成像器具有优异的单色性（能谱带宽小于1 eV）,适合于中低原子序数Z箍缩内爆负载的特征谱线单色图像诊断。     

Characterization of X‐ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

X‐ray gas attenuators are used in high‐energy synchrotron beamlines as high‐pass filters to reduce the incident power on downstream optical elements. The absorption of the X‐ray beam ionizes and heats up the gas, creating plasma around the beam path and hence temperature and density gradients between the center and the walls of the attenuator vessel. The objective of this work is to demonstrate experimentally the generation of plasma by the X‐ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X‐ray power absorption. The gases used in this study were argon and krypton between 13 and 530 mbar. The distribution of the 2p excited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s₅ state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X‐ray transmission. The results showed a plasma confined around the X‐ray beam path, its size determined mainly by the spatial dimensions of the X‐ray beam and not by the absorbed power or the gas pressure. In addition, the X‐ray absorption showed a hot central region at a temperature varying between 400 and 1100 K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X‐ray beam plays an essential role in the X‐ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.     

Observation and identification of X－ray（0．3－30Bnm) multiple－order diffraction spectra

ＯｂｓｅｒｖａｔｉｏｎａｎｄｉｄｅｎｔｉｆｉｃａｔｉｏｎｏｆＸ－ｒａｙ（０．３－３０ｎｍ）ｍｕｌｔｉｐｌｅ－ｏｒｄｅｒｄｉｆｆｒａｃｔｉｏｎｓｐｅｃｔｒａＦＥＮＧＸ．Ｐ；ＨＯＵＸ．Ｂ；ＺＨＡＮＧＺ．Ｑ；ＸＵＺ．Ｚ．（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅ...     

Understanding the absorption and emission spectra of borondipyrromethene dye and its substituted analogues

Borondipyrromethene (BODIPY) dye possesses a bright and long wavelength emitting fluorescent character with a wide spectral range from visible to near infrared region. In the present work, the spectral properties of BODIPY dyes were analyzed using ab intio and density functional theory methods. The ground and excited state geometries of BODIPY and its substituted analogues in chloroform medium, were optimized using the density functional theory (DFT) and singly excited configuration interaction (CIS) methods. Based on the ground and excited state geometries, the absorption and emission spectra have been calculated using time-dependent density functional theory (TDDFT) method. The TDDFT calculations have been performed using hybrid exchange correlation functionals B3LYP and M06-HF and long-range separated functionals LC-BLYP, LC-BOP, LC-PBE, LC-PBE0 and CAM-B3LYP. The solvent phase calculations were carried out using polarizable continuum model (PCM). The TDDFT investigation reveals that the substitution of acceptor, donor–donor, donor–acceptor–donor and phenyl group in BODIPY dye influence the absorption and emission spectra significantly.     

五通道Z箍缩等离子体K壳层线谱成像

采用5个针孔配接5块对数螺线晶体单色器方案,研制了一台五通道靶室内置式X射线单色成像器,并利用该成像器在阳加速器上成功获取了铝丝阵负载Z箍缩内爆等离子体的K壳层自辐射五通道单色线谱图像。该成像器结构紧凑,安装调节简便精准,能谱分辨力高（小于1.3 eV）,能够清楚分辨Al的类氦主共振线（1 598.4 eV）和互组合线（1 588.3 eV）,以及类氢主共振线（1729 eV）及其伴线（1 727.7 eV）光谱图像。由于阳加速器驱动能力有限,这些图像均由若干的离散热斑组成,并且大都集中在柱状等离子体轴线上,说明这些热斑附近的电子温度和密度较周围要高;类氦主共振线较类氢主共振线图像强度高、热斑区域大,反映了Z箍缩等离子体温度不够高,原子被激发到类氢离子的数量远少于类氦离子。     

等离子体发射和吸收系数的轴对称重建

在激光聚变靶丸等离子体诊断中,为了同时重建出等离子体发射系数和吸收系数的空间分布,建立了分层结构成像模型,利用LM（Levenberg-Marquardt）非线性最小二乘优化算法,提出了基于该模型的重建算法。数值模拟结果表明,该算法成功地重建出发射系数和吸收系数,而且重建精度高,明显优于不考虑吸收衰减影响的Abel逆变换重建结果。对于连续分布,当噪声标准差为0.01时,发射系数与吸收系数重建误差分别为0.17,0.22。