Surface plasmon characteristics of tunable photoluminescence in single gold nanorods

Light emission resulting from two-photon excited gold nanoparticles has been proposed to originate from the radiative decay of surface plasmon resonances. In this vein, we investigated luminescence from individual gold nanorods and found that their emission characteristics closely resemble surface plasmon behavior. In particular, we observed spectral similarities between the scattering spectra of individual nanorods and their photoluminescence emission. We also measured a blueshift of the photoluminescence peak wavelength with decreasing aspect ratio of the nanorods as well as an optically tunable shape-dependent spectrum of the photoluminescence. The emission yield of single nanorods strongly depends on the orientation of the incident polarization consistent with the properties of surface plasmons.     

激光诱导Ni等离子体发射光谱的空间演化特性研究

在350- 600nm 波长范围内测定了激光烧蚀Ni等离子体中Ni原子的空间分辨发射光谱.测定了385.83 nm发射光谱线的相对强度和STARK展宽及其随径向的变化特性。结果表明, 在沿激光束方向上, 当距离靶表面0-2.5mm范围内变化时,谱线的STARK展宽和谱线的强度都随距靶面距离的增大先增大,但增大到最大值后随距离的进一步增大而减小。谱线强度和STARK加宽的最大值都出现在离靶面约1.5mm处。     

激光诱导Ni等离子体发射光谱的空间演化特性研究

在350～600 nm波长范围内测定了激光烧蚀Ni等离子体中Ni原子的空间分辨发射光谱.测定了385.83 nm发射光谱线的相对强度和STARK展宽及其随径向的变化特性.结果表明,在沿激光束方向上,当距离靶表面0～2.5 mm范围内变化时,谱线的STARK展宽和谱线的强度都随距靶面距离的增大先增大,但增大到最大值后随距离的进一步增大而减小.谱线强度和STARK加宽的最大值都出现在离靶面约1.5 mm处.     

Determination of the three-dimensional orientation of single molecules

A simple method for real-time determination of the full three-dimensional orientation of the emission dipole of single molecules is presented. Introduction of a pi phase step in the back focal plane of the collector lens breaks the inherent symmetry, allowing the longitudinal dipole component to be measured. Experimental tolerances and the consequence of a nonzero bandwidth emission spectrum are also discussed. The scheme also allows for the longitudinal component of an electric field to be found experimentally.     

基于PbO/PbS特征发射光谱的铜冶炼过程检测方法研究

介绍了在铜冶炼时运用转炉火焰中氧化铅(PbO)和硫化铅(PbS)特征发射光谱强度比值进行过程检测(区分制矿渣阶段和制铜阶段)的一种方法。根据已知气体分子的特征发射光谱,确定了实测谱线中PbO和PbS的存在,并通过现场实验确定了制矿渣阶段的主要特征发射光谱来自PbS,而制铜阶段的主要特征发射光谱来自PbO。转炉冶炼时,PbO和PbS特征发射光谱强度的相对变化提供了铜冶炼过程的检测方法,通过利用特征发射光谱相对强度的比值可以区分炼铜过程中的两个不同阶段——制矿渣阶段(S期)与制铜阶段(B期)。在一个完整的炼铜周期中,利用光谱测量设备采集转炉火焰发射光谱,将噪声滤除后的PbO和PbS特征发射光谱用于过程检测,准确地完成了S期与B期的鉴别。理论和实验都证明基于发射光谱的铜冶炼过程检测方法是可靠的。     

Neutral particle emission from zinc oxide surface induced by high-density electronic excitation

Emission of neutral zinc and oxygen atoms and oxygen molecules emitted from zinc oxide surface by laser irradiation have been measured. It is found that the emission intensity starts to increase when the laser intensity exceeds a certain threshold value, indicating that the particle emission is a high density electronic excitation effect. The energy spectrum of emitted particles is found not to follow the Maxwellian distribution.     

狭缝微放电等离子体参数的光谱测量

利用平行管水电极介质阻挡放电装置,在氩气和空气混合气体中,得到了狭缝微放电等离子体。利用发射光谱法,研究了此放电中分子振动温度、分子转动温度和电子的平均能量随气体压强的变化。通过氮分子第二正带系(C3Πu→B3Πg)的发射谱线计算了氮分子的振动温度;利用氮分子离子(N2+)的第一负带系(B2Σu+→X2Σg+)的发射谱线计算了氮分子的转动温度;测量了氮分子离子391.4 nm和激发态的氮分子337.1 nm两条发射谱线的相对强度之比,研究了电子能量的变化。结果表明,当压强从60 kPa增大到100kPa,分子振动温度及分子转动温度均减小,氮分子离子谱线与激发态的氮分子谱线的强度之比亦减小。     

一种共轭聚合物单分子发色团吸收和发射特性动态演变过程的实时测量

利用频域信息重构的散焦宽场成像测量了Poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole](PFO-DBT)共轭聚合物单分子发色团的吸收与发射特性及其动态演变过程.通过调制用于激发共轭聚合物单分子的超短脉冲对的相对相位,对单分子荧光进行傅里叶变换的频域测量,跟踪发色团吸收偶极取向变化;通过测量散焦荧光成像光斑探测发色团发射偶极取向变化.研究发现, PFO-DBT共轭聚合物单分子发色团存在吸收和发射偶极取向均保持不变、其中之一变化以及两者同时变化三种情况.这种对共轭聚合物单分子发色团吸收和发射偶极取向演化过程的实时测量可用于分析共轭聚合物构象变化及其对能量转移过程的影响.     

Optical orientation effects in the secondary radiation of excitonic molecules

The spectrum of secondary radiation emitted from excitonic molecules under resonant two-photon excitation is investigated theoretically. Taking into account the optical orientation for the final exciton states of the emission process, we derive polarization and angular features of the radiation, reflecting directly the relaxation stage of the molecules.     

Sputtering of molecules during low-energy electron bombardment of alkali halides

The emission of molecules during bombardment of several alkali halides with a 540 eV electron beam has been investigated. Using a time of flight method the energy distributions of the halogen molecules have been measured at various temperatures of the target. The relative halogen molecule to atom ratio has also been examined as a function of the target temperature. It has been found that the molecules were formed from the atoms at the alkali halide surface. This process and the subsequent desorption of the molecules account for the experimental results.     

SERS studies on 1–4 dihydroxyanthraquinone at Ag electrode

Raman scattering studies on 1–4 dihydroxyanthraquinone (DHAQ) at Ag electrode have been carried out to investigate the enhancement in the spectral line intensity after adsorption. Charge transfer between the adsorbate and the substrate is more pronounced for certain normal modes of vibration. It is found that the DHAQ molecules are lying with their molecular plane on the top of the metal surface. Laser induced fluorescence spectra of DHAQ have also been analysed with a view to assign the relative orientation of absorption and emission dipoles.     

Theoretical Treatment of Electric and Magnetic Multipole Radiation Near a Planar Dielectric Surface Based on Angular Spectrum Representation of Vector Field

We have developed an analytic treatment of light emission properties of electric and magnetic multipoles near a planar dielectric surface, using angular spectrum representation of vector spherical waves. The results are described in terms of spatial rotation matrix elements, so that the angular distribution of light emission for higher order multipoles is easily obtained, which enables us to evaluate basic optical near-field problems such as electric dipole radiation with arbitrary orientation with respect both to surface and observation direction. The numerical results are in good agreement with our previous experimental results and the numerical results reported by Lukosz.     

Radiation of Gas Layer over Hot Surface

A method is presented for evaluation the radiation flux produced by a gas layer near a heated surface, where the gas temperature depends on a distance from the surface. This method refers to small temperature gradients and operates with an effective radiation temperature for each frequency, as well as with the width of the gas absorption band. These parameters are determined by the absorption spectrum of atoms or gas molecules, and also by the shape of the spectral line for the radiative transition between certain states of atomic particles of a gas. The possibilities of this method are demonstrated by examples of emission of photons from the solar photosphere, as well as emission of CO₂ molecules in the atmospheres of the Earth and Venus.     

Orientation Selective 2D-SIFTER Experiments at X-Band Frequencies

Frequency-correlated 2D SIFTER with broadband pulses at X-band frequencies can be used to determine the inter-spin distance and relative orientation of nitroxide moieties in macromolecules when the flexibility of the spin-labels is restricted. At X-band frequencies the EPR spectrum of nitroxides is governed by the strongly anisotropic nitrogen hyperfine coupling. For rigid spin-labels, where the orientation of the inter-connecting vector R correlates to the relative orientations of the nitroxide labels, the dipolar oscillation frequency varies over the EPR spectral line shape. Broadband shaped pulses allow excitation of the complete nitroxide EPR spectra. In this case, Fourier transform of the echo signal gives both fast and direct access to the orientation dependent dipole coupling. This allows determination of not only the inter-spin distance R, but also their mutual orientation. Here, we show the application of the frequency-correlated 2D SIFTER experiment with broadband pulses to a bis-nitroxide model compound and to a double stranded DNA sample. In both molecules, there is restricted internal mobility of the two spin-labels. The experimental results are compared to orientation selective pulsed electron double resonance (PELDOR) experiments and simulations based on a simple geometrical model or MD simulations describing the conformational flexibility of the molecules. Fourier transformation of the SIFTER echo signal yields orientation selective dipolar time traces over the complete EPR-spectral range. This leads to an improved frequency resolution and either to a reduced experimental measurement time or a larger span of frequency offsets measured compared to orientation selective PELDOR experiments. The experimental potential and limitations of the 2D SIFTER method for samples containing rigid spin-labels will be discussed.     

YVO4：Eu3+纳米微粒发射光谱与温度的关系

测量了非选择激发下YVO₄:Eu³⁺纳米微粒中Eu³⁺的⁵D₀→⁷F₂发射光谱随温度的变化.低温下的光谱是很多谱线叠加在一起形成的宽带;而室温下主要是与体材料相似的两条分离谱线.根据选择激发下YVO₄:Eu³⁺的发射光谱研究得到的结论,把发射光谱分解为两部分之和,一部分来自占据靠近纳米微粒中心的格位的Eu³⁺离子发射谱线具有与体材料相近峰值;另一部分来自占据靠近表面位置的Eu离子,发射分布在更大的光谱范围内.这两部分发光的相对强度随温度变化的分析表明,YVO₄:Eu³⁺纳米微粒发射光谱随温度的变化是由于靠近表面的Eu通过表面猝灭中心猝灭而引起的.     

Structure and dynamics of ordered water in a thick nanofilm on ionic surfaces

The structure and dynamics of water in a thick film on an ionic surface are studied by molecular dynamic simulations. We find that there is a dense monolayer of water molecules in the vicinity of the surface. Water molecules within this layer not only show an upright hydrogen-down orientation, but also an upright hydrogen-up orientation. Thus, water molecules in this layer can form hydrogen bonds with water molecules in the next layer. Therefore, the two-dimensional hydrogen bond network of the first layer is disrupted, mainly due to the O atoms in this layer, which are affected by the next layer and are unstable. Moreover, these water molecules exhibit delayed dynamic behavior with relatively long residence time compared with those bulk-like molecules in the other layers. Our study should be helpful to further understand the influence of water film thickness on the interfacial water at the solid-liquid interface.     

衬底温度对ZnMgO薄膜结构和光致发光性能的影响

利用超声喷雾热解方法以不同的沉积温度(450～550 ℃)在石英衬底上制备出一系列ZnMgO薄膜。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和光致发光谱(PL)表征了样品的晶体结构、表面形貌和光学性能。结果表明衬底温度对薄膜结构性能和光学特性影响显著。所有薄膜都呈六角纤锌矿多晶结构,其中在530 ℃条件下制备的样品C轴择优最明显,晶粒尺寸均匀,表面形貌平整,结晶质量最好。薄膜的光致发光谱显示随着温度的升高深能级跃迁范围逐渐减小,近紫外带边发光峰逐步出现。衬底温度为530 ℃时在374.5 nm处出现了明显的近紫外发光峰,且几乎没有明显的深能级跃迁出现。     

High resolution spectra of the red fluorescence in chemical oxygen-iodine laser

In our chemical oxygen-iodine laser(COIL)experiments we accidentally ob-served relatively strong red fluorescence while setting a hot metal wire in the cavity.The in-tensity of such emission is 2～3 orders of magnitude stronger than the initial O_2(~1A)dimerfluorescence.The fluorescence spectrum was measured with OMA and Bomem FT spectrome-ter respectively and the highest resolution of the measurement is 0.1cm~(-1).The emission maycome from O_4 molecules or an isomer of Cl_2O_2.     

MCNP模拟月表关键性元素γ射线与实测结果比较分析

嫦娥一号携带的γ射线谱仪传回大量能谱数据,对其分析与解谱是一个比较复杂的过程。针对此问题,提出按照月表γ射线来源的物理过程,分为月球表面天然放射元素、中子非弹性散射和中子俘获三部分。用MCNP程序模拟其在GRS中的能谱数据,将模拟结果叠加并与实测谱线对比,结果表明,模拟γ谱线能帮助辨识出实测谱线中的部分关键元素,例如~(40)K、~(214)Bi等。     

Optical anisotropy and photostability of polarizing films dyed with Brilliant Yellow

We obtained polyvinyl alcohol films dyed with Brilliant Yellow (BY) and have determined their spectral and polarizing characteristics in the short-wavelength region of the visible spectrum (400–430 nm). We have shown that BY imparts a polarizing power of ≥99% to the film. We measured the orientational parameters characterizing the degree of ordering of the polymer chains and the dye molecules for different BY content in the film. An increase in BY concentration above 0.3 wt.% is accompanied by a decrease in its orientational parameter, which is connected with aggregation of dye molecules and a change in the distribution of the molecular axes relative to the film orientation axis. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 466–472, May–June, 2009.