用于GaAs太阳能电池的NaYF4中Tb3+-Er3+耦合对的光谱转换

观测到一种以Tb³⁺-Er³⁺进行光谱转换的量子剪裁现象。一个高能紫外光子(Tb³⁺的⁷F₆→⁵L₁)被量子剪裁成两个低能光子:一个是近红外光子(Er³⁺的⁴I_9/2→⁴I_15/2),另一个是蓝色光子(Tb³⁺的⁵D₄→⁷F₆),它们两个 都可以被GaAs太阳能电池有效地吸收。量子剪裁效率高达188%,接近理论极限的200%。从Tb³⁺(⁵L₁→ ⁵D₄) 到Er³⁺(⁴I_15/2→⁴I_9/2)的能量传递的能量失配是237 cm^-1,比NaYF₄中的声子能400 cm^-1小,能量传递是近共振的。Tb³⁺施主间的能量迁移可以近似地用扩散模型处理, 从Tb³⁺-Er³⁺对之间能量传递的初始过程发现,偶极-偶极相互作用占主导地位。     

退火对Pb辐照Al2O3单晶发光特性的影响

研究了230MeV的²⁰⁸Pb²⁷⁺辐照Al₂O₃样品及随后在600,900,1100K高温条件下退火后的光致发光特性。从辐照样品的测试结果可以清楚地看到在波长为390,450nm处出现了强的发光峰。辐照量为1×10¹³ions/cm²时,样品的发光峰最强。经过600K退火2h后测试结果显示,380nm发光峰剧烈增强,而其他发光峰显示不明显。在900K退火条件下,380nm的发光峰开始减弱,而在360,510nm出现了明显的发光峰,至到1100K退火完毕后380nm的发光峰完全消失,而360,510nm的发光峰相对增强。从被辐照样品的FTIR谱中看到,波数在460~510cm^-1间的吸收是振动模式,经过离子辐照后,吸收带展宽,随着辐照量的增大,Al₂O₃振动吸收峰消失,说明Al₂O₃振动模式被完全破坏。1000~1300cm^-1之间为Al—O—Al桥氧的伸缩振动模式,辐照后吸收带向高波数方向移动,说明其振动模式受到影响。辐照剂量较小的样品,损伤程度相对较低,经退火晶化后,振动模式基本恢复到单晶状态;辐照剂量较高的样品,损伤程度大,退火处理后表面变得较粗糙,振动模式并未出现,说明结构破坏严重。     

YAG中Cr3+和Yb3+的发光特征以及Cr3+和Yb3+之间的能量传递过程

室温下观察了YAG:Cr³⁺,Yb³⁺材料在近红外区域的发光特性, 并通过对Cr³⁺:⁴T₂和Yb³⁺:²F_5/2能级辐射跃迁寿命以及它们布居时间的比较研究,提出了从Cr³⁺到Yb³⁺的能量传递机制,同时借助于能级图描述了从Cr³⁺到Yb³⁺的能量传递以及Cr³⁺和Yb³⁺的近红外发光过程。     

Energy Spectrum and Its Pressure-Induced Shift and g Factor of ZnS:Mn2+

By using strong-field scheme, the complete d⁵ energy matrix with D_2d symmetry has been constructed. Then, by diagonalization of this matrix at normal and various pressures,the whole energy spectrum [including the ground-state zero-field-splitting (GSZFS)], its PS and the g factor of the ground state for zns:Mn²⁺ have uniformly been calculated. According to the eigenfunctions and PS, the new assignments of five absorption bands have been given.The variation of tetragonal field with pressure makes a main contribution to the pressureinduced shift (PS) of GSZFS of zns:Mn²⁺, which supports the existence of tetragonal Jahn-Teller distortion in zns:Mn²⁺. It is found that when P≥62 kbar, t₂⁴(³T₁)e⁴T₁ merges with t₂e^{4 2}T₂, which has to be taken into account in the calculation of PS of the fifth band in the range of 1 bar ~ 95 kbar. It is demonstrated that the Mn²⁺ ions in ZnS:Mn²⁺ have tetrahedral coordination, and the difference between ζ and ζ' caused by the covalency effect is very important for GSZFS. The physical essentials of typical levels, GSZFS and their PS have been revealed. By taking into account the influence of covalency on t₂³(⁴A₂)e²(³A₂)⁴A₁ and t₂³(²E)e²(³A₂)⁴E, the positon of the third absorption band at normal pressure has been estimated.     

The contribution of 2N photon absorption in C(γ,2N) reactions for Eγ = 150–400 MeV

The ¹²C(γ,pn) and ¹²C(γ,pp) reactions have been studied using tagged photons of energy E_γ = 150–400 MeV. Recoil momentum distributions are compared to the results of Monte Carlo calculations based on a two-nucleon photon absorption model and two different phase space models. The ¹²C(γ,pn) data at low missing energy are consistent with absorption on 1p² and 1s1p nucleon pairs.     

Vacuum ultraviolet spectroscopy of Pr in CaAl4O7, LaMgAl11O19 and SrLaAlO4

The vacuum ultraviolet spectroscopy of Pr³⁺ doped CaAl₄O₇, LaMgAl₁₁O₁₉ and SrLaAlO₄ is reported. It appears that whenever the aluminate host lattice is excited directly, mainly exciton and 4f²–4f² [³P₀] Pr³⁺ emission are observed. When the excitation energy is lower, Pr³⁺ ions are excited selectively and 4f5d–4f² emission dominates. These observations can be explained by assuming that energy transfer from the host lattice to the Pr³⁺ ion takes place preferentially via an intermediate exciton state with an energy too low to reach the energetic Pr³⁺ 4f5d excited states.     

Cross section of the charged current reaction C(ve, e)Ng.s.

The charged current nuclear transition ¹²C(v_e, e⁻)¹²N_g.s. has been observed in the KARMEN experiment. The flux average cross section for v_e from μ⁺ decay at rest is determined to be σ = [8.1±0.9(stat.)±0.75 (syst.)]×10⁻⁴²cm². For the first time also the energy dependence of the cross section has been measured for neutrino energies up to 50 MeV.     

INFLUENCE OF C+-IMPLANTATION DOSE ON BLUE EMISSION AND MICROSTRUCTURES OF Si-BASED POROUS β-SIC

Crystal Si were implanted with different doses of C⁺ from 10¹¹ to 10¹⁷ cm^-2 at an energy of 50 keV. β-SiC precipitates were formed by thermal annealing at 1050 ℃ for 1 h and porous structures were prepared by electrochemical anodization. Under the excitation of ultraviolet, the samples, with C⁺ dose ≥10¹⁵ cm^-2 have intense blue emission which is stronger than the photoluminescence (PL) intensity of reference porous silicon (PS), and increases as C⁺ dose increases; the samples with C⁺ dose ≤10¹⁴ cm^-2 show similar PL spectra to those of PS. The blue peak intensity in PL spectra is correlated with the TO phonon absorption strength of β-SiC in infrared absorption spectra. The transmission electron microscopy study shows that the blue peak is also correlated with the microstructures. Because porous β-SiC is nanometer in size, it is suggested that the quantum confinement effect be responsible for the blue light emission.     

Nb XIII离子3d94s2, 3d94s4p, 3d94p2 组态能级结构与跃迁的理论研究

用准相对论Hartree-Fock方法对Nb XIII离子二电子激发组态3d⁹4s², 3d⁹4s4p, 3d⁹4p² 的能级结构做了全面系统的理论计算研究.在对已有研究结果分析的基础上, 运用最小二乘方法对径向积分参数进行了优化计算, 得到了与这些组态有关的电偶极允许跃迁的谱线波长和跃迁概率.计算结果与最新的实验值做了对比分析, 表明本文计算结果是准确的. 研究发现, 波长40.92 nm的谱线, 属于3d⁹4s(¹D)4p²F_7/2–3d⁹ (²D)4s^{2 2}D_5/2 的跃迁谱线, 而不属于3d⁹4s (¹D)4p⁴D_7/2–3d⁹(²D)4s^{2 2}D_5/2 的跃迁谱线, 即上谱项能级为²F_7/2, 而不是⁴D_7/2. 关键词： Nb XIII离子 二电子激发组态 谱线波长 跃迁概率     

ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

铥原子收敛于4f13(2F7/2o)6s(7/2,1/2)4o和4f13(2F7/2o)6s(7/2,1/2)3o偶宇称里德伯系列能级的电子关联效应

本文在多通道量子亏损理论框架下,利用相对论多通道理论,计算了铥原子收敛于4f¹³（²F_7/2^o）6s（7/2,1/2）₄^o和4f¹³（²F_7/2^o）6s（7/2,1/2）₃^o的三个偶宇称里德伯系列.通过将计算结果与美国国家标准与技术研究院数据进行比较,展示了两种类型的电子关联效应：1）里德伯系列之间的相互作用,导致里德伯系列的能级出现整体偏移;2）一个孤立的干扰态镶嵌在一个里德伯系列中,破坏了该里德伯系列能级的规则性.     

Spectroscopy of C

The ¹⁴C(t, p)¹⁶C reaction locates five new states in ¹⁶C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0⁺ and 2⁺ 2p-2h states, respectively. The 4.14 MeV state has J^π = 4⁺ and the 6.11 MeV state has J^π = 2⁺, 3⁻, or 4⁺.     

YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。     

Energy Spectrum and Its Pressure-Induced Shift and J-T Effect of ZnTe:Mn2+

By using strong-field scheme, the complete d⁵ energy matrix with symmetry has been constructed. Then, by diagonalization of this matrix at normal and various pressures,the whole energy spectrum [including the ground-state zero-field splitting (GSZFS)] and its pressure-induced shift (PS) of Znlb:Mn²⁺ have uniformly been calculated. The results are in very good agreement with experimental data. According to the eigenfimctions and PS, the assignments of four absorption bands have been given. By taking into account the dect of different deformations of t₂ and e radial wavefunctions on t₂³(⁴A₂)e²(³A₂)⁴ A₁ and t₂³(²E)e²(³A₂)⁴E, the position of the third absorption band at normal pressure has been estimated.The tetragonal field is important for GSZFS of ZnTe:Mn²⁺ and its PS, which supports the existence of tetragonal Jahn-Teller distortion in ZnTe:Mn²⁺ The physical essentials of typical levels, GSZFS and their PS have been revealed.     

Continuum absorption of vibrationally excited O2 from 200–320 nm

Cross sections for absorption from excited vibrational levels of the ground X³Σ^-_g state of molecular oxygen to the repulsive 1³Π_u state are given. The potential energy curve for the 1³Π_u state of O₂ is constructed to be consistent with predissociation data for the B³Σ^-u state and with recent ab initio calculations. In the photon wavelength range of 200–320 nm the cross sections are smoothly oscillatory and in no case larger than 1 × 10^-21 cm². In the region of the Schumann-Runge bands the cross sections are of order 0.4 × 10^-21 cm².     

icMRCI+Q理论研究BF~+离子电子态的光谱性质和预解离机理

采用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法,结合相关一致基组aug-ccpV5Z和aug-cc-pV6Z,计算了BF+离子前两个离解极限B~+(~1S_g)+(~2P_u)和B+(~3P_u)+F(~2P_u)对应的14个Λ-S态(X~2Σ~+,1~2Π,2~2Π,2~2Σ~+,1~4Σ~+,1~4△,1~4Σ~-,1~2△,1~2Σ~-,3~2Σ~+,1~4Π,2~4Π,2~4Σ~+和3~2Π)和30个Ω态的势能曲线.在势能曲线的计算中,考虑了旋轨耦合效应、核价相关和标量相对论修正以及将参考能和相关能分别外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的12个A-S态和28个Ω态的光谱常数,并且X~2Σ~+态的光谱常数与已有的实验结果符合.此外,计算了BF分子X~1Σ~+态到BF+离子X~2Σ~+,1~2Π和2~2Σ~+态的垂直电离势和绝热电离势,并且BF~+(X~2Σ~+)←BF(X~1Σ~+)的垂直电离势和绝热电离势与相应的实验结果非常符合.由X~2Σ~+,2~2Π,1~4Σ~+,3~2Σ~+和3~2Π态和其他的激发A-S态势能曲线的交叉现象,借助于计算的旋轨耦合矩阵元,首次分析了X~2Σ~+和3~2Π态的预解离机理以及2~2Π(v′≥9),1~4Σ~+(v′≥4)和3~2Σ~+(v′≥4)的振动能级受到其他电子态的微扰.计算了30个Ω态离解极限处的相对能量,并且与实验结果十分符合.最后计算了2~2Π(v′=0—9)—X~2Σ~+,2~2Σ~+(v′=0—2)—X~2Σ~+,(3)1/2—(1)1/2~(势阱一)和(2)3/2(v′=0—9)—(1)1/2~(势阱一)跃迁的Franck-Condon因子、爱因斯坦自发辐射系数和辐射寿命.     

SrZn2(PO4)2:Sn2+,Mn2+荧光粉的发光性质及其能量传递机理

采用高温固相法制备了SrZn₂(PO₄)₂:Sn²⁺(SZ₂P:Sn²⁺), SrZn₂(PO₄)₂:Mn²⁺(SZ₂P:Mn²⁺), SrZn₂ (PO₄)₂:Sn²⁺, Mn²⁺(SZ₂P:Sn²⁺, Mn²⁺) 荧光粉. 通过X射线衍射、激发和发射光谱详细研究了荧光粉的物相和发光性质. 在SrZn₂(PO₄)₂ 基质中, Sn²⁺离子发射光谱是峰值位于461 nm宽带谱, 归属于Sn²⁺离子的³P₁→¹S₀能级跃迁, SZ₂P:Mn²⁺激发光谱由基质吸收带(200–300 nm)和位于352, 373, 419, 431和466 nm的一系列激发峰组成, 分别对应Mn²⁺离子的⁶A₁(⁶S)→⁴E(⁴D), ⁶A₁(⁶S)→⁴T₂(⁴D), ⁶A₁(⁶S)→[⁴A₁(⁴G), ⁴E(⁴G)], ⁶A₁(⁶S)→⁴T₂(⁴G)和⁶A₁(⁶S)→⁴T₁(⁴G)能级跃迁, 因此, SZ₂P:Sn²⁺ 的发射光谱与SZ₂P:Mn²⁺的激发光谱有较大范围的重叠. 结果表明Sn²⁺对Mn²⁺发光有明显的敏化作用. 基于Dexter电多极相互作用能量传递公式和Reisfeld近似原理分析, 荧光粉SZ₂P:Sn²⁺, Mn²⁺中Sn²⁺-Mn²⁺离子之间的能量传递机理属于电四极-电四极相互作用引起的共振能量传递, 并计算出Sn²⁺-Mn²⁺离子之间能量传递临界距离R_c ≈ 1.78 nm. 通过改变Sn²⁺, Mn²⁺离子掺杂浓度, 实现了荧光粉发光颜色的调节, 在254 nm短波紫外激发下荧光粉发出较强的蓝白光. 研究结果表明SZ₂P:Sn²⁺, Mn²⁺荧光粉有望应用于紧凑型节能灯照明领域, 随着半导体紫外芯片技术的发展, 有潜力应用于未来的白光发光二极管照明领域.     

Na_2~+离子较低电子态势能曲线和光谱常数的理论研究

通过多组态相互作用方法,结合原子有效芯势与极化势,利用非收缩的高斯基函数,计算了Na_2~+分子对应最低9个解离限的36个电子态的势能曲线.基于计算获得的束缚态势能曲线,拟合给出了相应的光谱常数,并与已有的实验和理论结果进行了比较.同时,给出了部分电子态的振动-转动能级和一些同类态避免交叉点的信息.计算获得的光谱信息对冷原子分子光谱与动力学的研究具有参考价值.     

Splitting of the near infrared absorption bands of Sm in POCl3:SnCl4, POCl3:ZrCl4 and POCl3:TiCl4

The near infrared absorption spectra of Sm³⁺ in POCl₃:SnCl₄, POCl₃:ZrCl₄ and POCl₃:TiCl₄ consist of a series of bands, attributed to the ⁶H_5/2 → ⁶F_J transitions. Each one of these absorption bands is split into three components. The extent of splitting differs slightly from state to state. For each component of the ⁶F-multiplet the splitting decreases gradually from POCl₃:SnCl₄ to POCl₃:ZrCl₄ and POCl₃:TiCl₄. Energy differences between adjacent components of the near infrared absorption bands vary from a maximum of 166 cm⁻¹ to a minimum of 123 cm⁻¹. The band half-widths of the corresponding components vary from 86 to 120 cm⁻¹. At lower temperatures the intensity of the high energy component increases whereas the intensity of the entire absorption band envelope, associated with each component of the ⁶F-multiplet, remains almost constant. The splitting observed is attributed to the Stark splitting of the ⁶H_5/2-state of Sm³⁺ into three components, in conjunction with appropriate Stark splitting of the states of the ⁶F-multiplet.     

icMRCI+Q理论研究CF离子12个-S态和23个?态的光谱性质

采用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-ccpV5Z和aug-cc-pV6Z计算了CF~+离子第一离解极限C~+(~2p_u)+F(~2P_u)对应的12个∧-S态(X~l∑~+,a~3∏,1~3∑~+,1~3Δ,1~1∑~-,1~1∑~-,1~3∑~-,2~1∑~+,1~1∏,2~3∏,2~1∏和2~3∑~+)所产生的23个Ω态的势能曲线.计算中考虑了旋轨耦合效应、核价相关和标量相对论修正以及将参考能和相关能分别外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的9个∧-S态和16个Ω态的光谱常数,并且X~1∑~+,a~3∏~(势阱一)∧-S态的光谱常数与已有的实验结果非常符合.此外,计算了CF自由基X~2∏态到CF~+离子束缚和准束缚的9个∧-S态的垂直电离势和绝热电离势,并且CF~+(X~1∑~+)←CF(X~2∏)和CF~+(a~3∏(势阱一))←CF(X~2∏)的垂直电离势和绝热电离势与相应的实验结果也非常符合.由a~3∏,1~1∏态和其他激发∧-S态势能曲线的交叉现象,借助于计算的旋轨耦合矩阵元,分析了a~3∏~(势阱一),1~1∏~(势阱一)和2~1∑~+态的预解离机理.计算的23个Ω态离解极限处的相对能量与实验结果十分吻合.最后计算了(2)0+~(势阱一)(v'=0-5),(1)1~(势阱一)(v'=0-5)和(2)1~(势阱一)(v'=0)到X0~+态跃迁的Franck-Condon因子和辐射寿命.