Auger-vacancy satellites in the decay of 82Pb (RaD)

The L-Auger spectrum of ²¹⁰Bi from RaD (²¹⁰Pb) has been studied with a resolution of 0.18% and a very thin source but with some sacrifice in statistics. A total of 65 lines or line groups have been wholly or partially identified. The L₃-MM lines, most of which result from filling L₃ vacancies created by the L₁-L₃M_{4, 5} Coster-Kronig process, are displaced an average of −36±5 eV with respect to the energies expected from the L_{1, 2}-MM spectra. This effect is the Auger analogue of the phenomenon of X-ray satellites. The L₃-M₄M₅ and L₃-M₅M₅ displacements agree within experimental error with predictions from the displacements of the strongest L₁ and L₂ X-ray satellites. We suggest the term Auger-vacancy satellites for these displaced Auger lines to distinguish them from the weak lines of the K-LL spectrum for which we suggest the term Auger Intermediate-Coupling Satellites. The ratio (L₁-M₄M₅ Auger Line)/L₁-vacancies = R = 32.5±3.5, which may have importance in determining L₁ capture as distinct from L-capture, was also measured for the first time. The end-point of the low-energy beta spectrum of ²¹⁰Pb was found to be 17.0±0.5 keV.     

YVO_4∶Eu~(3+)@SiO_2核壳结构纳米复合材料的合成与表征

用沉淀法制备了尺寸约为8 nm的YVO4∶Eu3+纳米粒子,然后用反相微乳液法在YVO4∶Eu3+纳米粒子的表面包覆了一层Si O2壳。利用XRD、TEM、UV-Vis吸收光谱和光致发光光谱对合成的样品进行了表征。得到的复合物具有较好的核壳结构,通过改变硅酸四乙酯的用量可以改变Si O2壳的厚度。研究了Si O2壳对YVO4∶Eu3+发光性质的影响,结果表明:包覆和未包覆的样品在紫外光激发下都有Eu3+的特征发射;随着Si O2壳厚度的增加,发光强度和量子效率越来越低,Eu3+格位对称性越来越高。     

场发射显示器用蓝色YVO_4∶Tm~(3+)纳米荧光粉的制备及性能研究

采用溶剂热法成功地制备出了YVO4∶Tm3+纳米荧光粉,并用X射线衍射仪(XRD)、透射电子显微镜(TEM)、紫外分析仪、紫外可见(UV-Vis)吸收光谱和光致发光(PL)光谱对YVO4∶Tm3+纳米荧光粉进行测试和表征。实验结果表明,YVO4∶Tm3+纳米荧光粉可发出明亮的蓝光,色纯度和发光强度都很高,而且具有良好的热稳定性。因此,YVO4∶Tm3+纳米荧光粉是一种十分适用于场发射显示器的荧光粉。     

HoVO4相变的高压拉曼光谱和理论计算研究

利用高温固相反应法制备了纯相的HoVO₄,并在0–21.25 GPa压强范围内测定了HoVO₄的拉曼光谱. 通过分析其拉曼峰的频移和劈裂变化情况,发现HoVO₄在9.3 GPa发生相变. 根据第一性原理选取并优化相似体系的高压晶体结构,将其与HoVO₄的常压锆石矿型I4₁/amd结构进行了能量比较,确认HoVO₄ 相变结构为白钨矿型结构（I4₁/a）. 研究结果表明,HoVO₄具有ScVO₄和YVO₄体系的从锆石矿型结构（I4₁/amd）至白钨矿型结构的相变过程. 分析对应结构相的体积随压强的变化,发现体积坍塌对该相变起重要作用. 上述研究结果有助于了解HoVO₄的高压结构以及该材料在高压特殊条件下的应用. 关键词： 锆石矿型结构 白钨矿型结构 拉曼光谱 第一性原理     

Laser properties of different Nd-doped concentration Nd:YVO4 laser crystals

The laser outputs of 1.26, 0.95, 0.5 and 0.32 at% Nd-doped concentrations in Nd:YVO₄ crystal samples were performed under high pumping power of laser diode. The reason of different Nd-doped concentrations in Nd:YVO₄ crystals influencing on the laser output properties was explained. The intracavity double frequency laser outputs of Nd:YVO₄ crystal at 532 and 671 nm were also performed. Our experimental results show that the optimum Nd-doped concentration in Nd:YVO₄ crystal is about 0.5 at% under a pumping power of 30 W.     

采用L1/2稀疏约束的梅尔倒谱系数语音重建方法

提出了一种利用L_1/2稀疏约束从梅尔倒谱系数重建语音时域信号方法。从梅尔倒谱系数估计语音幅度谱是一个欠定问题,现有的方法均采用幅度谱最小均方误差估计或采用L1正则化进行幅度谱的稀疏约束。相比于L₁正则化模型,L_1/2的稀疏约束特性更强,为此,本文在从梅尔倒谱系数估计语音幅度谱时引入L_1/2正则化约束,并利用求解的稀疏幅度谱估计相位谱,最后利用估计的频谱重建时域语音信号。实验结果表明,与幅度谱最小均方误差法相比,本文算法所估计出的语音信号具有更高的语音质量;在噪声环境下进行语音重建实验,与L₁正则化幅度谱估计方法相比,本文算法重建的语音质量更好,表现出更好抗噪性。      

Soft X-ray emission study of thermally treated Ni(film)/4H–SiC(substrate) interface

Deposition of Ni as contact on 4H–SiC has been investigated. Ni/4H–SiC samples were annealed at temperatures of 600, 800 and 950 °C for 30 min and were non-destructively characterized by soft X-ray emission spectroscopy (SXES) using synchrotron radiation as excitation. Si L_2,3 SXE showed the formation of Ni₂Si for all annealing temperatures. The C K SXE indicated the formation of graphite and graphitic carbons at annealing temperatures of 950 °C and below 800 °C, respectively.     

A single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-fibre laser

We present a single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO_4 laser is suitable for use as a seed laser in some Lidar systems(e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO_4 laser at 2.05 μm.     

激光二极管抽运的Nd:YVO_4连续自拉曼1175nm激光器

报道了采用激光二极管端面抽运的Nd:YVO4晶体连续自拉曼激光器的实验研究.通过对晶体掺杂浓度及晶体结构的选择优化,减轻自拉曼晶体的热效应,实现了结构紧凑的1175 nm连续自拉曼激光器的高效运转.最终以两端键合的复合Nd:YVO4晶体作为自拉曼介质,在25.5 W的抽运功率下,获得了最高3.4 W的1175 nm连续拉曼光输出,光光转换效率为13.3%,拉曼阈值低至2.21 W,斜效率为14.6%.     

高效率LD端面抽运准连续355 nm激光器

报道了一台激光二极管（LD）端面抽运Nd：YVO₄晶体腔内倍频和腔外和频相结合的声光调Q准连续355 nm 紫外激光器。采用LD端面抽运双侧翼键合YVO₄基质的Nd：YVO₄晶体,在腔内置入Ⅰ类相位匹配的LiB₃O₅（LBO）晶体进行倍频实现1 064 nm和532 nm双波长准连续激光输出,通过消色差透镜将双波长激光聚焦耦合到Ⅱ类相位匹配的LBO 晶体中进行和频,并采用双向和频光路,获得了高效率、高光束质量、高重复频率的准连续355 nm 紫外激光输出。在抽运功率为28.6 W、重复频率为20 kHz时,355 nm激光最大输出功率4.2 W,脉宽为20.6 ns,光-光转换效率为14.7%,激光器光束质量因子M_x²和M_y²分别为1.29和1.23。     

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.     

Phase decomposition in nominal LaxCuO4 (x≤2.00) determined by extended x-ray absorption fine structure

Cu K-edge and La L₃-edge X-ray absorption spectra have been measured on a series of nominal La_xxCuO₄ samples with x≤2.00. The extended X-ray absorption fine structure (EXAFS) results show that the x<2.0 samples always consist of stoichiometric (La/Cu=2/1) La₂CuO₄ and CuO. The number of La vacancies in the La₂CuO₄ structure, if any, should be very small. The sensitivity of the EXAFS technique to impurity phases under favorable conditions is demonstrated.     

LD泵浦全固态608.1nm和频激光器

本文报道了一种全固态腔内和频608.1 nm激光器。在激光谐振腔两个分臂中,两支激光二极管分别泵浦Nd: YVO₄和Nd: YAG晶体,分别选择1 342 nm波长(Nd: YVO₄晶体的⁴F_3/2-⁴I_13/2谱线)与1 112 nm波长(Nd: YAG晶体的⁴F_3/2-⁴I_11/2谱线)振荡并进行腔内和频。通过优化谐振腔设计,腔内两个波长获得了较好的模式匹配。在两个分臂的交叠部分,利用LBO I类相位匹配进行和频,获得和频608.1 nm激光输出。实验表明,当Nd: YVO₄与Nd: YAG晶体泵浦功率分别为600和740 mW时,获得了功率为23.8 mW、波长为608.1 nm激光输出,激光输出稳定、噪声低。利用本文提出的和频结构是获得608.1 nm激光输出较为有效的方法。     

Surface and interface of Ti(film)/SiC(substrate) system: a soft X-ray emission and photoemission electron microscopy study

We have conducted a soft X-ray emission spectroscopy (SXES) and a photoemission electron microscopy (PEEM) study on the heat-treated Ti/4H–SiC system. This spectro-microscopy approach is an ideal surface and interface characterization techniques due to the non-destructive nature of SXES and the real-time surface imaging of PEEM.

The Si L_2,3 and C K soft X-ray emission spectra, which reflect Si (s+d) states and C p states, respectively, revealed formations of Ti₅Si₃ and TiC in the reacted interfacial region of Ti (50 nm)/4H–SiC(0 0 0 1) sample.

The surface of the Ti films on 4H–SiC samples during heat-treatment up to 850 °C was investigated by PEEM. The variation in brightness in the image of the sample was attributed to the surface deoxidation in the early stage of the treatment and to the formation of reacted region at the later stage. The darkening of the surface could be attributed to the formation of TiC and/or excess C atoms that could have migrated to the surface.     

端抽运Yb3+:YVO4激光准三能级理论模型研究

立足于Yb离子能级结构、谐振腔增益损耗和布居数分配情况, 利用爱因斯坦辐射理论和速率方程理论, 建立了适合Yb³⁺离子激光的准三能级理论模型. 该模型引入有效腔长增益贡献因子对腔内光强进行了从头计算, 获得了阈值方程. 利用此模型与Yb激光的实验结果相比较, 发现有效腔长对增益的贡献可以改变腔内损耗和粒子数反转的概率, 也继而影响激光阈值和输出功率效率. 应用于LD端抽运Yb³⁺:YVO₄激光实验中, 在971 nm LD抽运, 有效晶体长度 L=1 mm, 输出镜透过率对激光波长1016 nm为1%条件下, 获得阈值为1.1 W; 有效晶体长度L=2 mm, 输出镜透过率为10%条件下, 阈值获得为3.9 W. 关键词： 3+:YVO₄')" href="#">Yb³⁺:YVO₄ 准三能级模型 有效腔长增益贡献因子     

On the information depth of auger electron appearance potential spectroscopy

The information depth of AEAPS in comparison with AES was estimated using the overlayer technique. The strengths of the AES and AEAPS L₃ and L₁ signals of Cr and Ti were measured as a function of the Cr overlayer thickness on a Ti substrate. No significant differences between the information depths of both methods have been found. It follows that the information depth of AEAPS is basically limited by the mean free path of the primary electrons. Slight disagreement between the results obtained for the L₃ and L₁ subshells of Ti and Cr may indicate that the information depth of AEAPS could be modified by the kind of relaxation mechanism and the subsequent transport process.     

28.2 W波长锁定878.6 nm激光二极管共振抽运双晶体1064 nm激光器

报道了一种由波长锁定878.6 nm半导体激光器共振抽运两块不同掺杂浓度Nd:YVO4晶体串接的1064nm激光器,并与使用单块的低掺杂浓度晶体和高掺杂浓度晶体情况进行比较,实验表明利用波长锁定878.6nm半导体激光器共振抽运双晶体串接的方式,有利于降低晶体的热效应,提高光光转换效率.当抽运功率为40 W时,获得了28.2 W的1064 nm激光输出,光光转换率为70.5%,斜率效率为70.6%,相对吸收光的光光转换率76%,斜率效率为76.4%,同时该激光器在10?C—40?C的温度变化范围内具有极好的温度稳定性.     

Suppressing the preferential σ-polarization oscillation in a high power Nd:YVO_4 laser with wedge laser crystal

We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.     

Why are the band-like states suppressed in the M3–M4,5M4,5 super Coster–Kronig electron spectrum of Cu metal compared to those in the L3–M4,5M4,5 Auger electron spectrum?

The relative spectral intensity of the band-like two M_4,5-hole state to the atomic-like localized one is much suppressed in the coincidence M₃–M_4,5M_4,5 super Coster–Kronig (sCK) electron spectrum of Cu metal compared to the one in the coincidence L₃–M_4,5M_4,5 Auger electron spectroscopy (AES) spectrum. The M₃-hole lifetime width of Cu metal is calculated by an ab initio atomic many-body theory (the extended relaxed core random phase approximation with exchange). The calculated M₃-hole lifetime width of Cu metal agrees well with the experimental one. The M₃–M_4,5M_4,5 sCK decay width of Cu metal decreases much with delocalization of the two M_4,5 holes in the sCK final state, whereas the Auger decay width is fairly independent of localization and delocalization of the two M_4,5 holes in the Auger final state. Thus, the relative spectral intensity of the band-like state is much suppressed in the coincidence M₃–M_4,5M_4,5 sCK-electron spectrum of Cu metal compared to the one in the coincidence L₃–M_4,5M_4,5 AES spectrum.     

Up to 30 mW of broadly tunable CW green-to-orange light, based on sum-frequency mixing of Cr:forsterite and Nd:YVO4 lasers

Efficient generation of continuous-wave (CW) tunable light in the yellow region is reported. The method is based on sum-frequency mixing of a tunable Cr⁴⁺:forsterite laser with a Nd:YVO₄ laser. A periodically poled lithium niobate crystal was placed intra-cavity in a Nd:YVO₄ laser, and the Cr⁴⁺:forsterite laser was single-passed through the non-linear media. With this setup, it was possible to generate up to 3 mW of yellow light smoothly tunable from 573 to 587 nm. This is the highest output demonstrated to date for a tunable diode pumped solid-state CW laser in this wavelength region. The ways to improve the efficiency further are discussed.