D+OD+反应的量子动力学研究：交换通道和抽取通道的竞争

基于精确的势能面,研究D+OD⁺反应在0.0～1.0 eV碰撞能范围内的量子动力学. 用CS近似(centrifugal sudden approx-imation)的含时波包方法研究吸热的抽取反应通道(D+OD⁺→ O+D₂⁺)和热中性的交换反应通道(D+OD⁺→D+OD⁺),计算两个通道的反应几率、总积分反应截面和热速率常数. 发现在交换反应的反应路径上存在一个凸起结构. 计算的总角动量J=0时的波包分布的含时演化清楚地表明凸状结构对两个通道的动力学有非常重要的影响.     

用于白光LED的单一基质白光荧光粉Ca2SiO3Cl2:Eu2+，Mn2+的发光性质

用高温固相法合成了Eu²⁺，Mn²⁺共激活的Ca₂SiO₃Cl₂高亮度白色发光材料，并对其发光性质进行了研究. 该荧光粉在近紫外光激发下发出强的白色荧光，Eu^{2+中心形成峰值为419 nm和498 nm的特征宽带，通过Eu2+中心向Mn2+中心的能量传递导致了峰值为578 nm的发射，三个谱带叠加从而在单一基质中得到了白光. 激发光谱均分布在250—415 nm的波长范围，红绿蓝三个发射带的激发谱峰值分别位于385 nm，412 nm，370 nm和396 nm处，可以被InGaN管芯产生的紫外辐射有效激发. Ca₂SiO₃Cl₂:Eu2+，Mn2+是一种很有前途的单一基质白光LED荧光粉.}     

OCS+分子经由B2∑+←X2∏跃迁的光解离谱

制备出确定旋轨态的OCS⁺(X²∏)离子,在260～325 nm波长范围内研究了OCS^{+经由B2∑+←X2∏_3/2(000)和B2∑+←X2∏_1/2(000,001)跃迁的分质量光解离谱．由光解离谱得到OCS+(B2∑+)电子态的光谱常数υ1(CS stretch)=828.9(810.4) cm-1,υ2(bend)=491.3 cm-1和υ3(CO stretch)=1887.2 cm-1．在B2∑+←X2∏跃迁谱中只能观察到B2∑+(010)←X2∏_1/2(000)跃迁的谱峰, 而观察不到B2∑+←X2∏_3/2(000)跃迁的谱峰． 用X2∏电子态的(000)2∏_1/2和(010)2∑+_1/2电子振动能级之间的K耦合解释了这种B2∑+的υ2弯曲振动模的激发对X2∏电子态的旋轨分裂分量(Ω=1/2,3/2)的相关性}     

利用时间切片离子速度成像技术对AlO在193 nm的光解反应动力学研究

本文利用时间切片离子速度成像技术对AlO分子在193 nm下的光解反应动力学进行了研究. 实验通过产物Al⁺的离子速度和角度分布分析，发现了两个光解离反应通道，分别为中性AlO分子的单光子解离生成产物Al(²P_u)+O(³P_g)的通道，和AlO分子吸收两个光子电离产生AlO⁺进而解离生成产物为Al⁺(¹S_g)+O(³P_g)的反应通道. 每一个解离通道包括了AlO(v=0∽2)振动态的贡献，其中中性解离反应通道与离子解离反应通道相比，产物的各向异性参数对AlO的振动态依赖更大.     

AsO+同位素离子X2∑+和A2∏电子态的多参考组态相互作用方法研究

采用包含Davidson修正多参考组态相互作用(MRCI)方法结合价态范围内的最大相关一致基As/aug-cc-pV5Z和O/aug-cc-pV6Z, 计算了AsO⁺ (X²∑⁺)和AsO⁺(A²∏)的势能曲线. 利用AsO⁺离子的势能曲线在同位素质量修正的基础上, 拟合出了同位素离子⁷⁵As¹⁶O⁺和⁷⁵As¹⁸O⁺的两个电子态光谱常数. 对于X²∑⁺态的主要同位素离子⁷⁵As¹⁶O⁺, 其光谱常数R_e, ω_e, ω_ex_e, B_e和α_e分别为 0.15770 nm, 1091.07 cm^-1, 5.02017 cm^-1, 0.514826 cm^-1和0.003123 cm^-1; 对于A²∏态的主要同位素离子⁷⁵As¹⁶O⁺, 其T_e, R_e, ω_e, ω_ex_e, B_e和α_e分别为5.248 eV, 0.16982 nm, 776.848 cm^-1, 6.71941 cm^-1, 0.443385 cm^-1和0.003948 cm^-1. 这些数据与已有的实验结果均符合很好. 通过求解核运动的径向薛定谔方程, 找到了J=0时AsO⁺(X²∑⁺)和AsO⁺(A²∏)的前20个振动态. 对于每一振动态, 还分别计算了它的振动能级、转动惯量及离心畸变常数, 并进行了同位素质量修正, 得到各同位素离子的分子常数. 这些结果与已有的实验值非常一致. 本文对于同位素离子⁷⁵As¹⁶O⁺(X¹∑⁺), ⁷⁵As¹⁸O⁺(X¹∑⁺), ⁷⁵As¹⁶O⁺(A¹∏)和⁷⁵As¹⁶O⁺(A¹∏)的光谱常数和分子常数属首次报导.     

Br2+分子离子[1+1]双光子解离动力学

本文利用最近研制的低温离子阱-离子速度成像谱仪在冷离子束中研究了同位素质量分辨的⁷⁹Br₂⁺分子离子的[1+1]双光子激光解离动力学. 借助其1⁴Σ^-_u,3/2态为中间态使⁷⁹Br₂⁺共振吸收两个光子至4∽5 eV区域的高激发态并发生解离. 利用离子速度成像技术获得了光解产物⁷⁹Br⁺的二维速度分布和平动能释放谱. 通过平动能释放谱确定了不同解离能量处量子态分辨的解离产物通道分支比. 光碎片产物的角分布表明⁷⁹Br₂⁺分子离子的双光子解离是1⁴Σ^-_u,3/2态的ΔΩ=0平行跃迁至一个Ω=3/2高解离态发生的. 由于分子激发态中的强自旋-轨道耦合作用,高激发的四重态很可能参与到实验观测的光解过程.     

在193 nm关于Si2分子的离子解离动力学的成像研究

在193 nm的单色激光实验中,本文利用时间切片离子速度成像技术,研究了经193 nm双光子电离得到的Si₂⁺的解离反应动力学过程. 根据实验得到的Si⁺离子的速度成像,观测到了两种离子直接解离通道：Si(³P_g)+Si⁺(²P_u)和Si(¹D₂)+Si⁺(²P_u). 电子基态的Si₂分子处于v=0∽5的振动态上,其经过双光子电离后激发到Si₂⁺离子的多个电子激发态势能面,生成主要通道Si(³P_g)+Si⁺(²P_u),其中v=1的解离信号最强. 此外,由于势能曲线2²Π_g与3²Π_g相同对称性引起的避免性势能面交叉,生成次要反应通道Si(¹D₂)+Si⁺(²P_u). 通道Si(¹D₂)+Si⁺(²P_u)的产物亦可以由生成的基态Si₂⁺(X⁴Σ_g^-)吸收一个193 nm光子后解离得到,其对应产物则具有更大的动能.     

白光LED用LiSrBO3∶Sm3+材料的光谱特性

采用固相法制备了一种新型的白光LED用LiSrBO₃∶Sm³⁺红色发光材料,并研究了材料的光谱特性.材料的激发与发射光谱显示其能够被404 nm近紫外光激发,发射599 nm红光,很好的符合近紫外光激发下白光LED的需要.研究了Sm³⁺浓度对材料发射强度的影响,发现Sm³⁺浓度为3 mol%时,强度最大.添加Na⁺或K⁺也可提高LiSrBO₃∶Sm³⁺材料的发射强度.     

新型光存储材料Sr2SnO4: Tb3+, Li+ 的合成及其红外上转换光激励发光性能的研究

采用高温固相法获得了一种只具有 微弱余辉的新型电子俘获型光存储材料Sr₂SnO₄:Tb^{3 +}, Li ⁺. 发光性能研究结果表明: 该材料对980 nm的红外激光具有很好的上转换光激励信息读出响应, 同时292 nm紫外光为其最佳信息写入光源. 光存储性能研究结果表明: 该材料的浅陷阱较少, 因此其余辉发光很弱, 不到500 s; 另一方面, 该材料中存在大量的深蓄能陷阱. 因此, Sr₂SnO₄: Tb^{3 +}, Li⁺是一种具有较好实际应用价值的新型电子俘获型光存储材料. 此外, 还讨论了Sr₂SnO₄: Tb^{3 +}, Li⁺的光存储发光机理.     

N2O+离子A2Σ+电子态高振动能级的转动结构分析

利用一束波长为36055nm的激光，通过(3+1)共振多光子电离方法制备纯净的且处于X²Π_1/2，3/2(000)态的N₂O⁺离子，用另一束激光激发所制备的离子到第一电子激发态A²Σ⁺的不同振动能级，然后解离，通过检测解离碎片NO⁺强度随光解光波长的变化，得到了转动分辨的N₂     

Ca2SiO4:Dy3+材料的制备及其发光特性

采用高温固相法制备了Ca₂SiO₄:Dy³⁺发光材料.在365nm紫外光激发下,测得Ca₂SiO₄:Dy³⁺材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy³⁺掺杂浓度对Ca₂SiO₄:Dy³⁺材料发射光谱及发光强度的影响,结果显示,随Dy³⁺浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy³⁺浓度的增大,Ca₂SiO₄:Dy³⁺材料发光强度先增大,在Dy³⁺浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li⁺,Na⁺和K⁺对Ca₂SiO₄:Dy³⁺材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca₂SiO₄:Dy³⁺材料发射光谱强度的演化趋势相同,即Ca₂SiO₄:Dy³⁺材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li⁺,Na⁺和K⁺时,浓度分别为4mol%,4mol%和3mol%. 关键词： 白光LED 2SiO₄:Dy³⁺')" href="#">Ca₂SiO₄:Dy³⁺ 发光特性 电荷补偿     

Enhanced luminescence of Ca3B2O6:Dy phosphors by Na-codoping for LED applications

The Ca_2.95−yDy_0.05B₂O₆:yNa⁺ (0≤y≤0.20) phosphors were synthesized at 1100 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE), photoluminescence (PL) spectra and thermoluminescence (TL) spectra. The PLE spectra show the excitation peaks from 300 to 400 nm due to the 4f-4f transitions of Dy³⁺. This mercury-free excitation is useful for solid-state lighting and light-emitting diodes (LEDs). The emission of Dy³⁺ ions on 350 nm excitation was observed at 480 nm (blue) due to the ⁴F_9/2→⁶H_15/2 transitions, 575 nm (yellow) due to ⁴F_9/2→⁶H_13/2 transitions and 660 nm (red) due to weak ⁴F_9/2→⁶H_11/2 emissions. The PL results from the investigated Ca_2.95−yDy_0.05B₂O₆:yNa⁺ phosphors show that Dy³⁺ emissions increase with the increase of the Na⁺ codoping ions. The integral intensity of yellow to blue (Y/B) can be tuned by controlling Na⁺ content. By the simulation of white light, the optimal CIE value (0.328, 0.334) can be achieved when the content of Na⁺-codoping ions is y=0.2. The results imply that the Ca_2.95−yDy_0.05B₂O₆:yNa⁺ phosphors could be potentially used as white LEDs.     

Exploration of large amplitude motions in the Ca+Ar2 complex

ABSTRACT

We present a theoretical study of the ground electronic state potential of the Ca⁺Ar₂ complex and of its photoabsorption spectra, simulated at temperatures ranging between 20 and 220?K. These calculations exploit a Monte-Carlo (MC) method, based on a one-electron pseudo-potential approach. A pairwise additive potential fitted to coupled cluster ab initio points, is used to model the Ca⁺Ar₂ complex. Our study shows that the most stable form of Ca⁺Ar₂ is a bent C_2v structure, whereas the linear isomer is located at around 90?±?10?cm^?1 above in energy. The analysis of the photoabsorption spectra establishes that a structural transition from bent Ca⁺Ar₂ to linear ArCa⁺Ar occurs at T～100?K. Trends in binding energies of both isomers, bond lengths and bond angles are also discussed. Molecular orbital overlaps provide an explanation for the order of stability between the bent and linear structures.     

The electronic structure and photoluminescence properties of Ca2GeO4:Eu in ultraviolet and vacuum ultraviolet region

Ca₂GeO₄:Eu³⁺ phosphors were synthesized by the solid state method. The ultraviolet and vacuum ultraviolet excited photoluminescence properties were investigated in detail. It revealed that the emission of Ca₂GeO₄:Eu³⁺ comprised two parts: the red emission of Eu³⁺ and host defect emission in 330-550 nm. Ca₂GeO₄:Eu³⁺ presented intense excitation intensity at 163-200 and 466 nm, which suggested the potential applications in plasma display panels and light emitting diodes. The excitation spectra were studied to identify the photoluminescence mechanisms of Ca₂GeO₄:Eu³⁺. First principles calculation within the local density approximation of the density functional theory was applied to calculate the electronic structure and linear optical properties of Ca₂GeO₄.     

镱、钠共掺的氟化钙晶体在1050nm的可饱和吸收作用

通过在稳定连续波运转的Yb:YAG 激光器中插入不同掺杂浓度的新型钠、镱共掺的氟化钙晶体的对比性实验,证明了镱、钠共掺的氟化钙晶体在1050nm具有明显的可饱和吸收作用,从而解释了该晶体作为增益介质在该波段总是趋于自调Q运转的原因.Yb³⁺离子是该晶体可饱和吸收作用的主要因素,但是共掺入适当的Na离子可以明显改善晶体的调Q效果.优化共掺镱、钠离子的浓度和比例后的氟化钙晶体能够作为1050nm波段激光器的被动Q开关. 关键词： 镱、钠共掺氟化钙 可饱和吸收体 调Q     

281—332nm SO+2的光碎片激发谱研究

在超声分子束条件下，利用380.85nm的电离激光使SO₂分子经由［３＋１］共 振增强多光 子电离(REMPI)制备纯净的分子离子SO⁺₂(²A ₁(000))，用另一束解离激光在281 —332nm扫描获得了光解碎片激发(PHOFEX)谱.获得的光碎片SO⁺激发谱基本可以 归属为SO ⁺₂(,)←SO⁺关键词： +₂')" href="#">SO⁺₂ 光解离 光碎片激发谱     

Up-conversion white light of Tm/Er/Yb tri-doped CaF2 phosphors

Tm³⁺/Er³⁺/Yb³⁺ tri-doped CaF₂ phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm², the chromaticity coordinates of the UC light of the phosphor Ca_0.885Tm_0.005Er_0.01Yb_0.1F₂ fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed.     

The concentration quenching and crystallographic sites of Eu2+ in Ca2BO3Cl

A yellow phosphor, Ca2BO3CI：Eu2＋, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f65dl→4f7 transition of Eu2＋. Eu2＋ ions occupy two types of Ca2＋ sites in the Ca2BO3C1 lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2＋ in Ca2BO3C1. The emission intensity of Eu2＋ in Ca2BO3C1 is influenced by the Eu2＋ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.     

Emission analysis of Pr and Tm: Ca2Gd2W3O14 phosphors

5 mol% of Pr³⁺ and Tm³⁺ ions activated calcium gadolinium tungstate (Ca₂Gd₂W₃O₁₄₎ phosphors were synthesized by traditional solid state reaction method. Crystalline phase structure was identified from the X-ray diffraction (XRD) profiles. From the scanning electron microscopy (SEM) images, we have observed the agglomeration of the particles, and average grain size is around 40-300 nm. Using the energy dispersive X-ray analysis (EDAX) and Fourier transform infrared (FTIR) spectra, identified the elements and functional groups present in the prepared phosphors. The emission spectrum of Pr³⁺: Ca₂Gd₂W₃O₁₄ powder phosphors have shown an intense red emission at 615 nm with the excitation wavelength λ_exci=450 nm and thus these red color emitting powder phosphors are used as one of the components in the preparation of WLEDs. The excitation spectrum of Tm³⁺: Ca₂Gd₂W₃O₁₄ powder phosphor has shown a ligand to metal charge transfer (W-O) band (LMCT) within the WO₄²⁻ group. Emission spectrum of Tm³⁺: Ca₂Gd₂W₃O₁₄ phosphors have shown blue emissions at 453 nm (¹D₂→³F₄).