Si中S0/Se0,S0/Te0和Se0/Te0对的电子结构

利用紧束缚近似下的格林函数方法,讨论了Si中硫属元素混对杂质(即S⁰/Se⁰,S⁰/Te⁰和Se⁰/Te⁰)基态的电子结构。混对杂质在Si禁带中引入两个A₁能级,其中成键性的A₁能级位置在反键性的A₁能级之上。数值计算得到的混对杂质能级与实验符合得相当好。理论分析表明,在Si中测到的那些未定的比最近邻混对杂质能级更浅的能级(S⁰/Se⁰(X₁),S⁰/Te⁰(X₁),Se⁰/Te⁰(X₁)…)不是由非最近邻位型的混对杂质引入的。本文还指出了一个极性分子放入Si晶体中,两个不同原子间s波函数的转移方向与通常极性分子相反,并讨论其物理原因。 关键词：     

氨分子在000和201带的选择光离解

本文利用脉冲紫外激光(UV)选择激发氨分子到?¹A″₂电子激发态的两个最低振动能级ν′₂=0和ν′₂=1(ν₂振动),然后检测新生态H原子的飞行谱(TOF),研究了氨分子的光碎片动力学。光谱证实了最近所测的离解能D₀⁰(H-NH₂)=4.645eV;绝大多数生成的NH₂(X²B₁)基处于非振动激发,但是具有围绕a惯性轴的高度转动激发。通过NH₃(?)的ν′₂=1光离解产生的NH₂(X)基具有较高的内部激发,并且显示了在N=K_a转动能级上的反转布居。 关键词：     

Si中S~0对、Se~0对和Te~0对的电子结构

利用紧束缚近似下的格林函数方法,讨论了Si中(S~0)_2,(Se~0)_2及(Te~0)_2基态的能级和波函数。分析了几种不同的观点。(S~0)_2,(Se~0)_2及(Te~0)_2均在禁带中引入一个对称性的A_(1g)能级和一个反对称性的A_(2u)能级,二者都是填满的。现有实验观测到的是较高的A_(1g)能级。从理论上指出了对称性的A_(1g)能级反而高于反对称性的能级的原因。而Si中(Se_2)~ 的g因子测量值和(S_2)~ ,(Se_2)~ 的ESR实验结果也支持本文的观点。     

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.     

Pr3+在SBN晶体中的发光特性

通过测量Ｐｒ：ＳＢＮ晶体的吸收光谱和荧光光谱来确定Ｐｒ³⁺在ＳＢＮ晶体中的能级位置。由于Ｐｒ³⁺离子占据晶体中的不同格位而引起荧光带呈现双峰结构。测量荧光寿命随温度的变化关系，表明Ｐｒ³⁺在ＳＢＮ晶体中 ³Ｐ₀态的无辐射弛豫主要是 ³Ｐ₀→¹Ｄ₂多声子弛豫过程。 关键词：     

NaLa(MoO4)2∶Eu3+的水热调控合成与发光特性研究

采用水热法合成了不同粒径的NaLa(MoO₄)₂∶Eu³⁺微晶.通过调节乙二醇浓度和反应时间,研究了NaLa(MoO₄)₂∶Eu³⁺微晶的形貌演变过程,在水热条件下180 ℃反应16 h获得了均一梭子形NaLa(MoO₄)₂∶Eu³⁺微晶,其晶粒长度约为2.0 μm.荧光光谱分析表明,Eu³⁺取代了NaLa(MoO₄)₂中La³⁺的格位, Eu³⁺在613 nm处红光发射(⁵D₀–⁷F₂跃迁)的浓度猝灭机理是电偶极-电四极相互作用,并发生了Eu³⁺( ⁵D₁ ) + Eu³⁺(⁷F₀ )→ Eu³⁺( ⁵D₀ ) + Eu³⁺(⁷F₃) 交叉弛豫,由此导致浓度猝灭. 关键词： 钼酸盐 水热法 稀土离子 发光     

红色长余辉材料Zn3(PO4)2：Mn2+,Ga3+的合成及光谱性质

采用高温固相法合成α、β和γ-Zn₃(PO₃)₂:Mn²⁺,Ga³⁺(ZPMG),XRD分析表明,高温合成过程中淬火条件有利于β相的形成,退火条件有利于γ相的形成。三种磷光粉的激发光谱分别位于246nm(α)、234nm(β和γ)的宽带谱。α相的发射光谱为位于508nm的锐线谱,β和γ相的发射光谱均存在两个谱带,分别位于508nm的绿色光谱区和616nm的红色光谱区。两种发射均归属为Mn²⁺的⁴T₁(⁴G)→⁶A_1g(⁶S)跃迁,但是由于Mn²⁺在Zn₃(PO₃)₂结构中的配位数不同,故发光颜色及强度均不同。对于余辉发射,只能观察到红色余辉光谱。     

Ce3+, Mn2+共掺的Ca4Y6 (SiO4)6F2的发光性质和能量传递

采用高温固相法制备了Ca_4-xY_5.95 (SiO₄)₆F₂:0.05Ce³⁺, _xMn^{2 +}系列荧光粉,并对其发光性质以及Ce³⁺, Mn^{2 +}在Ca₄Y₆ (SiO₄)₆F₂ (CYSF)基质中的能量传递过程进行了研究.相结构研究表明: CYSF属于一种基于磷灰石结构的类质同象化合物.CYSF: 0.05Ce³⁺, _xMn²⁺荧光粉在200–373 nm为宽带激发光谱,Ce³⁺和Mn²⁺在408 nm和602 nm的发射峰分别由Ce³⁺的5d→4f的跃迁和Mn²⁺的⁴T₁ (⁴G)→ ⁶A₁ (⁶S)的跃迁产生.光谱重叠现象以及荧光寿命测试结果证明了Ce³⁺对Mn²⁺具有敏化作用,能级结构分析进一步证实该体系中存在Ce³⁺→Mn²⁺的能量传递过程,可有效地将Ce³⁺的蓝光转换为红橙光. 关键词： 磷灰石 发光性质 能量传递     

ZnS:Ho3+的辐射跃迁和无辐射过程

本工作研究了Ho³⁺离子在宽禁带半导体ZnS中的辐射跃迁和无辐射过程。用发射谱线的积分光强和激发态寿命获得ZnS:Ho³⁺的强度参数Ω_λ,同时计算了九个激发态的辐射跃迁几率和能级寿命。另外,通过在不同温度下测定Ho³⁺离子⁵G₆,³K₈,⁵F₂,⁵F₃和⁵S₂(⁵F₄)能级的发射光强和寿命的方法,研究了这几个激发态间的无辐射过程,其中⁵G₆,³K₈,⁵F₂和⁵F₃这四个能级是处于热平衡状态,而⁵F₃与⁵S₂(⁵F₄)能级间存在五个声子((1/n)ω_Lo=351cm^-1)参与的多声子弛豫过程。 关键词：     

非晶锂离子导体B2O3-Li2O-LiCl一Al2O3中VO2+的电子自旋共振

两种非晶锂离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃-0.1V₂O₅(x=0.05和0.15)的电子自旋共振谱研究表明:(i)ESR线型是高斯型,证实V₂O₅添加量适当;(ii)超精细结构来源于VO²⁺络离子,具有四角对称性,属C_4v群。越精细耦合张量的平行分量平均值A_//=0.0175cm^-1,垂直分量A_⊥=0.0063cm^-1。由g_//(g_⊥)求出其基态²B_2g与第一激发态²E_g的能级间距△₁=2.46×10⁴ cm^-1,基态与第二激发态²B_1g的能级间距△₂=3.03×10⁴ cm^-1;(iii)变温实验证实:Al₂O₃组分较少(x=0.05)的非晶ESR强度比x=0.15的非晶高3倍至2倍,而Al₂O₃组分越多则ESR强度随温升下降越小。     

Si中D3d对称性态密度分布和缺陷对电子结构

本文考虑了晶体中总的电子态密度在低对称性下用点群不可约表示基函数分解的问题,并给出了Si中用D_3d群不可约表示基函数分解最近邻两原子总态密度的计算结果。结合在位势近似Koster-Slater格林函数方法,文中将计算结果用于Si中双空位和硫属元素杂质对(S₂⁰,Se₂⁰和Te₂⁰)缺陷态电子结构的讨论。讨论得到的结果是:与点缺陷和缺陷对的深缺陷态对称性相匹配的部分态密度的分布是相似的;在态密度对缺陷能级的驱赶作用下,S₂⁰等的A^s能级在A^s能级之上,双空位的E_g能级在E_u能级之上,这种情况与通常双原子分子成反键能级位置完全相反;所讨论的缺陷对的波函数在Bloch空间的分布情况与对应的点缺陷类似。 关键词：     

Fluorescence spectra of matrix-isolated Se2

Laser induced fluorescence spectra are reported for samples of natural selenium and of the separated ⁷⁸Se and ⁸⁰Se isotopes in Ar and Kr matrices. The B(0_u⁺) → X(0_g⁺) and B(1_u) → X(1_g) systems of Se₂, already known in the gas, are observed by both single photon and biphotonic excitation considerably red-shifted in the matrices. The A(0_u⁺) → X(0_g⁺) emission of Se₂, not observed in the vapor, appears in the matrices with its origin near 15 100 cm^?1. Another system with ν₀₀ = 24 429 cm^?1 and ω″_e = 538 cm^?1 is thought to belong most probably to some polyatomic Se_n molecule.     

Accurate spectroscopic calculations of the 19 Λ-S states and 36 Ω states of the BC+ cation

This work computed the potential energy curves of 19 Λ-S states, which arose from the first five dissociation limits of BC⁺ cation, B⁺(¹S_g) + C(³P_g), B⁺(¹S_g) + C(¹D_g), B⁺(¹S_g) + C(¹S_g), C⁺(²P_u) + B(²P_u), and B⁺(¹S_g) + C(⁵S_u). The calculations were done for internuclear separations from 0.08 to 1.07 nm. The potential energy curves of 36 Ω states yielded from these Λ-S states were also calculated. Core-valence correlation and scalar relativistic correction, basis set extrapolation as well as Davidson correction were accounted for. Of these Λ-S states, the c¹Σ⁺, D³Π, 2¹Π, 2³Σ⁺, 2¹Δ, 3¹Σ⁺, and 4¹Σ⁺ had double wells; the 3³Π and 3¹Π states had three wells; the C³Σ^? and D³Π states were inverted with the spin-orbit coupling effect included; and the second wells of c¹Σ⁺, D³Π and 3¹Σ⁺ states, the second and the third wells of 3³Π state as well as the third well of 3¹Π state were very weakly bound, which well depths were smaller than 400 cm^?1. The spectroscopic parameters were determined for all the states. The vibrational properties were predicted only for some weakly bound states. The spin-orbit coupling effect on the spectroscopic parameters was evaluated.     

Experimental determination of the potential energy curves of the I(3/2u) and I(3/2g) states of Kr+ 2

The I(3/2u) and I(3/2g) states of Kr⁺ ₂ have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following (2 + 1′) resonance-enhanced multiphoton excitation via the 0⁺ _g Rydberg state located below the Kr?([4p]⁵5p[1/2]₀) + Kr(¹S₀) dissociation limit of Kr₂. From the positions of a large number of vibrational bands in the spectra of the ⁸⁴Kr₂ and ⁸⁴Kr-⁸⁶Kr isotopomers, the adiabatic ionization potentials (IP(I(3/2u)) = 112672.4 ± 0.8cm^?1, IP(I(3/2g)) = 111 395.0 ± 1.4cm^?1), the dissociation energies (D ⁺ ₀(I(3/2u)) = 368.8 ± 2.0cm^?1, D ⁺ ₀(I(3/2g)) = 1646.2 ± 2.3cm^?1) and vibrational constants for both ionic states have been determined. Potential energy curves have been extracted which perfectly reproduce all experimental observations and are accurate over a wide range of energies and internuclear distances. The equilibrium internuclear distances (R ⁺ _e(I(3/2u)) = 4.11 ± 0.04 Å, R ⁺ _e(I(3/2g)) = 3.35 ± 0.10 Å) have been derived by comparing the intensity distribution in the PFI-ZEKE photoelectron spectra to calculated Franck-Condon factors. The dissociation energy of the I(3/2g) state and the equilibrium internuclear distance of the I(3/2u) state differ markedly from previously reported values.     

Accurate theoretical spectroscopic investigations of the 20 Λ-S and 58 Ω states of O2+ cation including the spin–orbit coupling effect

The potential energy curves (PECs) are calculated for the 20 Λ-S states (X²Π_g, A²Π_u, B²Σ^?_g, a⁴Π_u, b⁴Σ^?_g, b′⁴Π_g, c⁴Σ^?_u, 1²Σ⁺_g, 1²Σ⁺_u, 1²Σ^?_u, 1⁴Σ⁺_g, 1⁴Σ⁺_u, 1⁴Δ_g, 1⁴Δ_u, 1⁶Σ⁺_g, 1⁶Σ⁺_u, 1⁶Π_g, 1⁶Π_u, 2⁴Π_g and 2⁴Π_u) of O₂⁺ cation and their corresponding 58 Ω states. Of these 20 Λ-S states, the 1⁶Π_u state is found to be repulsive. The 1²Σ⁺_g, 1⁴Σ⁺_u, c⁴Σ^?_u and 1⁴Δ_u states are found to possess the double well. The b⁴Σ^?_g, 1⁶Σ⁺_g, 1⁴Σ⁺_u, a⁴Π_u, A²Π_u, 1⁶Π_g and 2⁴Π_g states are found to be inverted with the spin–orbit coupling effect included. The b′⁴Π_g, 1⁶Π_g, 1⁶Σ⁺_g, 1⁴Σ⁺_u and 1⁴Δ_u states, and the second well of the 1²Σ⁺_g state are found to be the weakly bound states. The b′⁴Π_g state is found to possess one well with one barrier. The PECs are calculated by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction in combination with the aug-cc-pV6Z basis set. The core–valence correlation and scalar relativistic corrections are included. The convergent behaviour of present calculations is discussed with respect to the basis set and theoretical level. The spin–orbit coupling effect is accounted for. The PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated, and compared with available measurements. It demonstrates that the spectroscopic parameters reported here can be expected to be reliably predicted ones.     

The Contribution of Raman Scattering to the Fluorescence of the Polyene Antibiotic Amphotericin B

Fluorescence has recently been applied to the analysis of the molecular organization state of the polyene antibiotic amphotericin B (AmB) in solution or in lipid membranes. The polyene chain of AmB monomer gives rise to two fluorescence emissions; S₁(2¹A_g) → S₀(1¹A_g) between 500 and 700 nm, S₂(1¹B_u) → S₀(1¹A_g) between 400 and 500 nm. However, Raman scattering might interfere with the S₂ → S₀ emission fluorescence due to the weak fluorescence quantum yield and close proximity to the exciting lines. In fact, we show here that a change in the excitation wavelength results in a shift of three emission bands, an effect which excludes their assignment to fluorescence. These bands originate from the water Raman at 3382 cm^-1and AmB resonance Raman at 1556 and 1153 cm^-1. As a consequence, some former conclusions on the molecular organization state of AmB should be reconsidered.     

Absorption and fluorescence spectra of C<Subscript>60</Subscript> fullerene concentrated solutions in hexane and polystyrene at 77–300 K

The locations of the 0₀⁰ 0_0^0 -bands for S₁← S₀ and S₁ → S₀ transitions have been found for C₆₀ solutions in hexane. It is shown that the profile of the S₁ ← S₀ band is mainly shaped by h_u(4), t_1u(4)- and h_g(1), a_g(2)- modes that are active in absorption. Bands involving the h_u(4)- and t_1u(4)-modes in the emission process have also been identified in the fluorescence spectrum. The appearance of the 0₀⁰ 0_0^0 -band in the forbidden 1¹T_1g ← 1¹A_g transition is explained by symmetry reduction in the C₆₀+environment system due to the interaction of electrons with local phonons. The temperature coefficients of the red shift for the 256.3- and 328.3-nm bands of allowed ¹T_1u ← 1¹A_g transitions for C₆₀ in hexane are equal to –1.45 and –0.46 cm^–1·K^–1, respectively. The peak and half-width values of the 337.2-nm band for C₆₀ in polystyrene remain unchanged on cooling to 77 K. Absorption in the 700–800-nm region for concentrated hexane solutions of fullerene at 292 K results from the production of (C₆₀)_n-clusters.     

Electron-vibrational energy exchange in collisions of electronically excited N2(A 3Σ u + ) molecules with Zn(X 1 S) atoms

The interaction matrix between the N₂ molecule in the X ¹Σ _g ⁺ and A ³Σ _u ⁺ states and the Zn atom in the ¹ S and ³ P states calculated earlier by the asymptotic method was used to find the rate constants for the electron-vibrational energy exchange N₂(A ³Σ _u ⁺ , v) + Zn(¹ S) → N₂(X ¹Σ ₈ ⁺ , v′) + Zn(³ P). The calculations were performed by the transition state method, and the probabilities of transitions between intersecting electron-vibrational terms of the system in motion along the reaction coordinate were determined by the Landau-Zener equation. The calculated electron excitation transfer constants between N₂(A ³Σ _u ⁺ , v = 1, 0) and Zn(¹ S) over the temperature range 300–900 K were on the order of 10^?11?10^?12 cm³/s.     

Dipole moment functions for electronic transitions from ion-pair states of the second tier of molecular iodine

The emission spectra caused by the transitions from the ion-pair states and f0 _g ⁺ and G1_g of the I₂ molecule are obtained by excitation of individual rovibronic levels of the molecule by the method of optical-optical double resonance. The emission spectra from the state F0 _u ⁺ populated due to collisions I₂(f) + I₂(X) are also measured. By modeling the experimental emission spectra, the dipole moment functions for the electronic transitions f _g ⁺ -B0 _u ⁺ , A0 _u ⁺ , and B″0 _u ⁺ ; G1_g-A0 _u ⁺ and B″0 _u ⁺ ; and F0 _u ⁺ -X0 _g ⁺ and a′0 _g ⁺ of the iodine molecule are reconstructed.