转动传能中NH2(~A)精细结构态变化的研究

利用高分辨光谱技术观察了NH2(~2A A,090)423(F1/F2)在单次碰撞条件下的精细态色散荧光光谱,发现NH2(~2A A1)在与闭壳层分子碰撞传能过程中,母能级的自旋-转动耦合守恒,从实验上直接证实了在开壳层-闭壳层分子碰撞过程中电子自旋为一旁观者的假设;由于长程作用力造成子能级具有保持原来自旋-转动耦合的倾向.     

NH2(A~2A1, 090,423)的电子猝灭和转动态-态传能

在束-气和束-束实验条件下,详细研究了NH2(A2A1,090,423)自由基分别与Ar,N2,O2和NH3碰撞引起的电子态猝灭和转动态-态传能,获得了总的猝灭截面σQ(分别为≤0.17、0.26、0.30和0.48 nm2),以及相对转动态-态传能截面.利用碰撞络合物模型计算的电子猝灭截面与实验测得的截面具有基本相同的趋势,表明长程吸引势在猝灭过程中起着重要的作用.同时还发现,转动态-态传能中相对截面随着碰撞对的折合质量的减小而下降.由于NH3具有较大的偶极矩以及O2的开壳层电子结构使得猝灭截面增大,而转动态-态传能截面减小.     

NH2(A2A1,090,423)的电子猝灭和转动态-态传能

在束 气和束 束实验条件下,详细研究了NH2(A1,090,423)自由基分别与Ar,N2,O2和NH3碰撞引起的电子态猝灭和转动态 态传能,获得了总的猝灭截面σQ (分别为≤0.17、0.26、0.30和0.48 nm2),以及相对转动态 态传能截面.利用碰撞络合物模型计算的电子猝灭截面与实验测得的截面具有基本相同的趋势,表明长程吸引势在猝灭过程中起着重要的作用.同时还发现,转动态 态传能中相对截面随着碰撞对的折合质量的减小而下降.由于NH3具有较大的偶极矩以及O2的开壳层电子结构使得猝灭截面增大,而转动态 态传能截面减小.     

NH_2(~2A_1,090,4_(23))的电子猝灭和转动态-态传能

在束-气和束-束实验条件下,详细研究了NH_2(~2A_1,090,4_(23))自由基分别与 Ar,N2,O2和 NH3碰撞引起的电子态猝灭和转动态-态传能,获得了总的猝灭截面σQ (分别为≤ 0.17、 0.26、 0.30和 0.48 nm~2),以及相对转动态-态传能截面 .利用碰撞络合物模型计算的电子猝灭截面与实验测得的截面具有基本相同的趋势,表明长程吸引势在猝灭过程中起着重要的作用 .同时还发现,转动态-态传能中相对截面随着碰撞对的折合质量的减小而下降 .由于 NH_3具有较大的偶极矩以及 O_2的开壳层电子结构使得猝灭截面增大,而转动态-态传能截面减小 .     

三维H+H2(v,j)→H2(v′,j′)+H反应中复合态生成及产物转动态分布的量子散射理论研究

用排列通道线性组合-散射波函数(LCAC-SW,linear combination of arrangement channelsscattering wavefunction)量子反应散射方法计算了H+H2(v,j)→H2(v′,j′)+H三维态-态反应几率,分析了反应体系的复合态生成(或能量共振结构),并由产物的转动态分布解释了能量共振的起源来自于平动态-内态之间的干涉效应.     

传能反应O(1D)+CO2(1Σ+g)→O(3P)+CO2(1Σ+g)中间物机理的理论研究

利用ab initio 量子化学方法研究了自旋禁阻的传能反应O(1D)+CO2(1Σ+g)→O(3P)+CO2(1Σ+g)的反应机制, 通过中间化合物CO3的单、三重态的势能面交叉点的确认, 证明了中间物传能机理的可行性. 同时计算了交叉点处的自旋-轨道偶合和面间跃迁几率, 进一步证明了中间化合物CO3的形成在传能过程中的重要作用.     

电化学条件下喹喔啉-2(1H)-酮C(3)-H功能化的研究进展

喹喔啉酮及其衍生物是一类重要的氮杂环化合物,广泛存在于具有各种生物活性的天然产物、药物及功能材料中,因此,喹喔啉酮的C-H功能化引起了化学工作者的广泛关注.电化学合成无需外加氧化还原试剂,直接利用电子这一清洁试剂参与氧化还原反应,具有反应条件温和及原子经济性好等特点,十分符合绿色化学符合绿色化学和可持续发展的要求....     

碱性条件下顺(2-乙酰胺基-1-溴-2-(对-甲氧基苯基)乙基)膦酸二乙酯的1,2消除反应

碱性条件下顺(2-乙酰胺基-1-溴-2-(对-甲氧基苯基)乙基)膦酸二乙酯的1;2消除反应;消除反应; 胺基溴化反应; 膦酸酯; 二维核磁共振谱     

无溶剂条件下对甲基苯磺酸铝高效催化合成4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮

以芳香醛、芳香酮和尿素为原料,对甲基苯磺酸铝为催化剂,在90_oC、无溶剂条件下“一锅法”反应,高效合成了一系列4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮。产品结构通过IR,₁H NMR,₁₃C NMR和元素分析进行了表征。该方法具有操作简单、反应时间短、产率高、反应条件温和、不使用任何有机溶剂、催化剂廉价易得且可重复使用等优点,为标题化合物的合成提供了一种简便高效的绿色新途径。     

Defects and Luminescence Behavior of Cubic F23 [(NH4(18-Crown-6))4MnX4] [TlX4]2 (X=Cl, Br) Crystals

Luminescence from [(NH₄(18-Crown-6))₄MnBr₄][TlBr₄]₂ (1), [(NH₄(18-Crown-6))₄MnCl₄][TlCl₄]₂ (2), [(NH₄(18-Crown-6))₂MnBr₄] (3), and [(NH₄(18-Crown-6))₂MnCl₄] (4) was studied in search of new insights regarding crystal defects in 2. Emission from 3 and 4 is normal Mn²⁺(⁴T₁(⁴G)→⁶A₁); that of 2 (λ_max≈520 nm at ca. 300 K and 560 nm at 77 K) is unusual and temperature dependent. Thermal barriers (kJ/mol, assignment): green emission of 1 and 2, T<150 K (1-2, NH⁺₄ rotations), 150<T<250 K (7-14, energy migration among [MnX₄]²⁻), 250<T<300 K (26-35, rotations of 18-Crown-6)); yellow emission of 2: T;<250 K (7-8, energy migration among [MnX₄]²⁻), T>250 K (29 kJ/mol, defect-to-Mn²⁺(⁴T₁(⁴G)) back energy transfer). Crystal data for 4: Space group P2₁/c; Z=4; a=20.173(1) Å; b=9.0144(8) Å; c=20.821(1) Å; β=98.782(5)°; V=3741.9(8) ų; R_w=0.059; R=0.054.     

紫外激发Sr1-x-yMgP2O7:xCe3+,yTb3+荧光粉的发光特性及能量传递

采用高温固相法合成了Sr1-x-yMgP2O7:xCe3+,yTb3+荧光粉.研究了荧光粉的晶体结构、发光特性、荧光寿命、能量传递机理和荧光粉的热稳定性.研究结果表明:在SrMgP2O7基质中,Ce3+的发射峰值为398nm,Tb3+的主发射峰值为545nm,它们分别属于5d-4f跃迁和5D4→7F5跃迁.Ce3+和Tb3+共掺时,Ce3+和Tb3+通过电偶极子-电偶极子相互作用发生能量传递,能量传递的临界距离为0.614nm.通过计算得到单掺杂Ce3+、Tb3+时热猝灭过程的激活能分别为0.122和0.111eV,Tb3+离子的发光热稳定性比Ce3+离子的好.     

Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure

Missing VO₂(A) usually occurs during the preparation of VO₂ polymorphs. This leads to an ambiguous understanding of the transformation between VO₂ polymorphs. The calculation of the ground state energies for different VO₂ polymorphs indicated that there is only a small energy gap between VO₂(A) and VO₂(R), which destined that the transformation from VO₂(A) to VO₂(R) should be pressure sensitive. This hypothesis was verified during the synthesizing of VO₂ polymorphs by reducing V₂O₅ with oxalic acid through hydrothermal treatment process. Selective formation of pure phase VO₂(A) or VO₂(R) was achieved by controlling the hydrothermal pressure through varying the filling ratio at 270 °C. It was found that a filling ratio over 0.5 favors the formation of pure VO₂(R) while a reduced filling ratio to 0.4 or lower results in the formation of VO₂(A). Based on our experiments, VO₂(B) nanobelts were always first formed and then it transformed to VO₂(A) by assembling process at increased temperature or extended reaction time. Under further higher pressure, the VO₂(A) transformed spontaneously to VO₂(R) initialized from the volume shrinkage due to the formation of denser VO₂(R).     

Theoretical Study of Interaction Between S2 and SiHx (x=1, 2, 3) in Porous Silicon

The interaction between S₂ molecule and SiH_x (x=1, 2, 3) in porous silicon is investigated using the B3LYP method of density functional theory with the lanl2dz basis set. The model of porous silicon doped with CH₃,Si-O-Si and OH species is built. By analyzing the binding energy and electronic transfer, we conclude that the interaction of S₂ molecule with SiH_x (x=1, 2, 3) is much stronger than the interaction of S₂ molecule with CH₃ and OH, as S₂ molecule is located in different sites of the model. Using the transition state theory, we study the Si₂H₆+S2→H₃SiH₂SiS+HS reaction, and the reaction energy barrier is 50.2 kJ/mol, which indicates that the reaction is easy to occur.     

Observation of Interference Effects in (e, 2e) Electron Momentum Spectroscopy of SF6 (cited: 1)

Two-dimensional electron density map (2D map) of binding energy and relative azimuthal angle (i.e., momentum) for the outer-valence molecular orbitals of SF₆ has been measured by a highly sensitive electron momentum spectrometer with noncoplanar symmetric geometry at the impact energy of 1.2 keV plus binding energy. The experimental electron momentum profiles for the relevant molecular orbitals have been extracted from the 2D map and interpreted on the basis of the quantitative calculations using the density functional theory with B3LYP hybrid functional. For the outermost F2p nonbonding orbitals of SF₆, the interference patterns are clearly observed in the ratios of the electron momentum profiles of molecular orbitals to that of atomic F2p orbital.     

CF自由基5pπE2Пr(ν’=1)←X2П(ν’’=0)带的转动分析

The two-photon resonance-enhanced multiphoton ionization spectrum between 285 and 288.5 nm of the 5pπE2Πr(v’=1)←X2Πr(v’’=0) band of CF radical is reported. The band is rotationally analyzed, and the spectroscopic constants of the state are first derived: σ0 = 69566.38±0.52 cm-1, A'v= 46.4±0.3 cm-1, B'v= 2.565±0.017 cm-1, D' v = (8.6±1.2)×10-6cm-1.     

(NH4)2Ce(NO3)6 as an inexpensive,eco-friendly,efficient catalyst for the synthesis of 5-substituted 1-H tetrazoles from nitriles

Ceric ammonium nitrate (CAN) is found to be a suitable, inexpensive, and effective non-toxic catalyst for a smooth (3+2) cycloaddition of organic nitriles with NaN₃ to afford 5-substituted 1H-tetrazoles in excellent yields. Shorter reaction times, easy work-up, and substantial and pure product formation are the key advantages of the present method.     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of NOx by ammonia 1. TPD test of γ-Al2O3, TiO2 (anatase) and alumina-supported vanadia catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of γ-Al₂O₃, TiO₂ (anatase) and alumina-supported vanadia catalyst samples has been investigated using temperature-programmed desorption (TPD). When the vanadia loading was increased, the fraction of the acid sites providing the NH₃ adsorption in the high-temperature state decreased. At the same time, the fraction of the medium temperature state significantly increased.     

Rotational cooling of Li 2 ( 1 S g + ) molecules by ultracold collisions with a helium gas buffer

The very weak interaction of Li₂ with He atoms has been obtained from accurate ab initio calculations and is here analyzed in terms of its anisotropic features. Quantum scattering calculations of the rotational inelastic de-excitation cross sections are carried out using a recently proposed multichannel treatment, the modified variable phase method, implemented by the authors and applied here to ultralow collision energies. General conclusions on the low efficiency of a He buffer gas in cooling down molecular rotations in this system are presented and analyzed.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail.This work is affectionately dedicated to Prof. Jean-Louis Rivail on the occasion of his university retirement. We wish our friend many more happy years of research and the continued opportunity of guiding young scientists.     

Gas phase and solution state stability of complexes L…M, where M = Cu, Ni, or Zn and L = R−C(O)NHOH (R = H, NH2, CH3, CF3, or Phenyl)

The structure and gas-phase metal affinities (M = Cu²⁺, Ni²⁺, and Zn²⁺) of formohydroxamic acid derivatives R–C(O)NHOH (R = H, NH₂, CH₃, CF₃ and Phenyl) were studied using the B3LYP/6-311+G(d,p) method of DFT theory. In order to evaluate the conformational behavior of these systems in water, we carried out CPCM-SCRF optimization calculations at the B3LYP/6-311+G(d,p) levels of theory. The obtained optimized geometries and interaction affinities of the gas and solution phase were compared. The following order of stability was found for ionic complexes of the transition metals: Cu²⁺ > Ni(t)²⁺ > Zn²⁺. The same stability order would be expected according to the Irving–Williams order of stability constants. The high-spin complexes of the Ni²⁺ were more stable than the low-spin complexes. The solvent effect reduced the observed relative stability of individual metallic complexes of substituted hydroxamic acids.