[Au25(SR)18]-团簇的相干振动动力学研究

利用飞秒时间分辨光谱,可观测叠加在电子态动力学上的相干振动动力学. 从金团簇的相干振动中,不仅能提取电子与振动的耦合信息,也能得到力学性质和电子结构,进而有望实现微小质量探测等应用. 本文利用飞秒时间分辨的瞬态吸收探测了[Au₂₅(SR)₁₈]^-团簇的相干振动动力学,通过对相干振动的频率、相位、波长分布的详细分析进一步揭示了其来源. 在[Au₂₅(SR)₁₈]^-团簇的飞秒瞬态吸收动力学中可以观测到频率为40 cm^-1和80 cm^-1的两种振动,均来源于团簇中心Au₁₃核的振动. 通过对相干振动的相位分析发现频率为80 cm^-1的振动来自于对电子态之间吸收频率的调制,而频率为40 cm^-1的振动来源于对电子态之间吸收强度的调制. 同时,研究发现[Au₂₅(SR)₁₈]^-团簇相干振动的频率对其表面配体不敏感,该振动是来源于Au₁₃核的本征性质.     

N2O在142.5-147.5 nm射流冷却吸收光谱揭示的解离动力学

在射流冷却分子束下, 测量了142.5～147.5 nm N₂O分子C^{1∏态的吸收光谱,观测到清晰的振动序列结构,振动频率间隔约为500 cm-1. 结合理论计算的电子态势能面结构,这个振动序列被标识为解离电子态C1∏的弯曲振动激发. 傅立叶变换得到了相应的轨道周期为65 fs,而通过Lorentzian线型拟合获得了各振动峰对应的能级寿命约为20 fs.}     

N,N-二甲基硫代乙酰胺S3(ππ*)态的衰变动力学 (cited: 1)

采用共振拉曼光谱和完全活化空间自洽场方法研究了N,N-二甲基硫代乙酰胺在被激发至S₃(ππ^*)态后的衰减动力学. 指认了紫外吸收光谱和振动光谱. 获得了乙腈、甲醇和水溶剂中不同激发波长下的A带共振拉曼光谱,以探测Franck-Condon区域的结构动力学. 开展了CASSCF计算以确定低能单重激发态和锥形交叉点的电子激发能和优化几何结构. 通过共振拉曼强度分析和CASSCF计算获得了结构参数、A带结构动力学和S₃(ππ^*)态衰减机制. 提出了主要衰减通道为_3,FC(ππ^*)→S₃(ππ^*)/S₁(nπ^*)→_1(nπ^*).     

振动和转动激发对N2在Fe(111)表面解离吸附的影响

N₂的解离化学吸附是工业合成氨的速控步骤. 基于最近构建的六维势能面,本文研究了N₂的初始振动激发和转动激发在Fe(111)表面的反应性的作用. 由于该反应具有重要的量子效应,通过六维量子动力学计算研究了入射能量低于1.6 eV 时振动激发的效应. 并采用准经典轨线计算揭示了高入射能量下的振动和转动激发的影响. 通过这些研究发现增加平动能量在一定程度上能提高解离几率,振动激发或转动激发能更有效地促进解离. 这项研究为重原子分子-表面反应的模式特异性动力学提供了有价值的见解.     

不同能量的氦原子与同位素分子H2(D2，T2)碰撞分波截面的理论计算

用Tang-Toennies势模型和密耦近似方法计算了不同能量下惰性气体原子He与H₂及其同位素D₂，T₂替代碰撞体系的振转激发碰撞截面. 通过分析He-H₂(D₂，T₂)各碰撞体系分波截面的差异，总结出在H₂分子的对称同位素替代情形下He-H₂(D₂，T₂)碰撞体系分波截面随量子数和体系     

从可溶性单源分子前驱体采用溶胶凝胶法制备ZnO/TiO2 纳米复合物

合成了单源分子前驱体Cl₂TiZn(dmae)₄ (dmae为2-二甲基乙醇胺),并以乙醇为溶剂,加入等摩尔量的水对其进行可控水解得ZnO/TiO₂纳米复合凝胶,经pH=9沉淀,在200、400和600 oC 烧结得到不同的产物T₂₀₀、T₄₀₀、T₆₀₀. XRD分析表明未烧结产物为无定形粉末并随着烧结温度升高晶型改善. ZnO呈纤锌矿结构(六方晶系),TiO₂呈板钛矿型结构(正交). BET分析和扫描电镜表明颗粒的大小随着烧结温度的提高而增加. 红外光谱证明Zn-O和Ti-O的特有的振动频率,OH基团烧结后的产物中被去掉. 所有的样品都显示良好的光催化活性, 且T₆₀₀活性最高.     

Wavelength-dependent Photodissociation Dynamics of Benzaldehyde

利用飞秒泵浦-探测方法结合飞行时间质谱研究了苯甲醛在不同泵浦波长260、271、284和287 nm下的超快动力学. 在S₂区(λ<284 nm),受激分子首先经过内转换过程到S₁高振动态,实验观察到这个过程随着S₂态分子振动能量的增加而变快,可能源于高振动能级密度导致S₂与S₁之间内转换加快. 双指数拟合的第二个过程(约600 fs)认为可能是由于内转换后在S₁态发生的振动     

重离子反应出射碎片之间激发能分配的研究

根据相干表面激发模型(CSEM)^[1—8],本文对于重离子反应出射碎片之间激发能分配作了分析.对于E_Lab=476MeV的 ⁵⁶Fe+²³⁸U反应和E_Lab=1565MeV的⁸⁶Kr+²⁰⁸Pb反应,本文讨论了出射碎片之间激发能分配的计算结果.     

25MeV/u 40Ar+natAg、209Bi反应中热核的温度和激发能测量

在25MeV/u ⁴⁰Ar+^natAg、²⁰⁹Bi反应中,用4个PPAC和11组望远镜完成了关联裂变碎片与发射轻粒子的符合测量,角关联描绘为两个被探测到碎片折叠角θ_ff的函数,线性动量转移〈LMT〉由测量到的角关联推出.将符合测量得到的对应于不同窗的后角轻带电粒子能谱用Maxwell分布来拟合其谱的后沿,经过一些修正,由能谱得到热核的初始温度T_int,在考虑反应Q值和预平衡发射的修正之后,可以得到不同窗所对应的激发能.实验结果表明,在⁴⁰Ar+^natAg、²⁰⁹Bi反应的中心碰撞中激发能分别为4.2、2.4MeV/u,而温度达6.1、5.5MeV,在半中心碰撞中激发能为3.5、1.9MeV/u,温度可达5.8、4.8MeV.     

PH, PD和PT分子常数理论研究

采用内收缩多参考组态相互作用(MRCI)方法和包含Davidson修正(+Q) 的MRCI方法结合相关一致基aug-cc-pV5Z研究了PH (X³Σ^-, a¹Δ和A³∏)分子的势能曲线. 在同位素质量识别的基础上对势能曲线进行拟合, 得到PH, PD和PT分子各个电子态的光谱常数(T_e, R_e, ω_e, ω_ex_e, α_e和 B_e). 通过与已有实验数据的比较发现, 本文的结果与实验结果非常一致. 对于PH, PD和PT分子的Σ^-电子态, 计算得到了J = 0时的前12个振动态. 对于每一个振动态, 还分别计算了它的振动能级、惯性转动常数和离心畸变常数. 与其他理论结果和实验数据进行比较可知, 本文的结果更精确、更完整. 文中PD和PT分子的光谱常数和分子常数均属首次报导.     

225∽260 nm波段溴化氰光解动力学系统性研究

本文报道了在自行搭建的时间切片离子速度成像装置上进行的225∽260 nm波段内溴化氰光解动力学的研究. 在该波段内选取了若干溴原子(²P_3/2或²P_1/2)的共振线对产物溴原子的共振电离并采集其切片影像,得到了光解产物的总平动能谱,进而获得了产物氰基的振转态布居等信息. 本文发现了在Br^*通道,产物氰基的内能激发比Br通道低;Br和Br^*通道产物氰基振动的最高布居分别为v=0和1. 另外,还发现对于Br通道,溴化氰分子在长波处与短波处解离时,氰基产物的振转激发差异很大,这揭示了其显著不同的光解动力学.     

Energy partitioning in photodissociation and photosensitization

The molecular dynamics of photodissociation and of electronic vibrational/translational energy transfer have been investigated in terms of an impulsive ‘half-collision’ model, modified to accommodate the possibility of changes in the potential energy functions (force constants) of the separating fragments. The model, which is suitable for any system which is suddenly prepared on a repulsive potential energy surface (e.g. following electronic excitation or radiationless transition), has been applied to the quenching of Hg(6³P₁) by CO and NO and to the photodissociation of ICN. Experimental data and alternative theoretical treatments are available for each of these systems. The new model is able to achieve a remarkable agreement with observation in the Hg/CO and NO systems by assuming the intermediate formation of a Hg(6³P₀) - CO or NO complex in which the C-O or N-O bond order increases by ～ 0·6. Model calculations for the quenching of Cd and Zn(³P₀) suggest that the distributions over final states would be very similar to that for Hg(³P₀).

A re-appraisal of the near U.V. photo-dissociation of ICN indicates that CN radicals should be formed preferentially in the òπ electronic state; those observed in the ground state should be vibrationally excited whether they appear as primary photo-products or not.

In general, changes in the equilibrium bond length of the molecular fragment as the system transfers onto the repulsive potential surface, are crucial in determining both the level of vibrational excitation and the detailed distribution over final states. When the molecular fragment has a large force constant the ‘steepness’ of the potential surface is relatively unimportant.     

Photodissociation dynamics of the methylsulfinyl radical at 248 nm

The photodissociation dynamics of jet-cooled methylsulfinyl radicals, CH₃SO, at 248?nm have been investigated using molecular beam photofragment translational spectroscopy. The primary channel is CH₃S?+?O, which occurs via the initially prepared excited CH₃SO state by rapid cleavage of the S-O bond to produce ground state products. The minor SO?+?CH₃ channel has two components in comparable proportions: a fast feature corresponding to rapid C-S cleavage on the excited state to produce CH₃ and electronically excited SO, and a slow feature due to internal conversion of CH₃SO followed by statistical dissociation on the ground electronic state. Statistical ground state dissociation also produces small amounts of CH₂SO, likely sulfine, and H-atoms.     

全维高精度势能面上F+CH3OH反应的产物振动态分布

甲醇与氟原子之间的抽氢反应可以生成HF和CH₃O、CH₂OH自由基等产物. 该反应在环境化学、燃烧化学、辐射化学和星际化学中都非常重要. 基于之前构建的全维高精度势能面,本文采用准经典轨线方法研究了该典型反应的动力学. 特别是使用正则模式分析方法确定了多原子产物CH₃O和CH₂OH的振动态分布. 研究发现,当反应物处于振转基态时,CH₃O和CH₂OH主要分布在基态. 当反应物CH₃OH的OH伸缩模式激发为第一激发态时,产物CH₂OH的OH伸缩模式、扭转模式、H₂CO 面外弯曲模式及其组合会被有效激发. 在两条通道中,可用能量大部分都流入HF的振动能和产物的平动能,而自由基产物CH₃O或CH₂OH只得到非常少的能量,与实验结果一致,这也表明了自由基的旁观者性质.     

Methanol laser lines from torsionally excited co stretch states, and from OH-bend, CH3-rock, and CH3-deformation states

Using a quasi-CW CO₂ oscillator-amplifier combination with peak power 300 Watt, we have generated FIR laser emission in weak absorption bands of CH₃OH. 40 new lines are reported, and their wavelengths are measured with a relative accuracy of 5×10^–5. A total of 72 lines are assigned. 34 of these involve torsional n=1, 2, and 3 states of the CO stretch and the vibrational ground state. The remaining lines are associated with the CH₃-rock, OH-bend, and CH₃-deformation modes. The latter are located 1460 cm^–1 above the ground state, and are pumped by simultaneous vibrational excitation and torsional deexcitation.     

甲烷分子电子碰撞电离和解离的实验研究

本文利用反应显微成像技术(reaction microscope)研究了54 eV电子入射甲烷分子导致的电离解离过程,详细分析了电离解离产生的CH⁺₂,CH⁺,C⁺离子碎片的动能分布情况.实验结果表明,该入射能量下产生CH⁺₂,CH⁺,C⁺离子碎片主要贡献来自2a₁内价轨道电子的直接电离过程产生的离子态(2a< 关键词： 反应显微成像谱仪 电离解离 能量沉积 动能分布     

High resolution Fourier transform infrared spectroscopy on CH2DI and CHD2I: evaluation of the ground state constants and analyses of the C-I stretching bands ν3

Abstract

The high resolution (0.0010cm^?1) Fourier transform infrared spectra of the partially deuterated methyl iodide molecules CH₂DI and CHD₂1 have been recorded and analysed in the ν₃ band regions around 510cm^?1. The fundamental band ν₃ is associated with the stretching of the C-I bond and the spectra appear therefore as an asymmetric rotor hybrid a/b-type band and hybrid a/c-type band for CH₂DI and CHD₂I, respectively. About 4700 transitions in the case of CH₂DI and about 3900 transitions in the case of CHD₂I have been assigned. The ground state rotational constants of CH₂DI and CHD₂I have been obtained using the ground state combination differences calculated from the assigned ν₃ transitions and 16 microwave transitions from literature. The S reduced Watson's Hamiltonian has been used in the calculations. In addition, the upper state parameters describing the v₃=1 vibrational states of these molecules have been determined. The obtained ground state constants as well as the upper state parameters have been compared to the corresponding constants of the symmetric top species CH₃I and CD₃I     

CALCULATIONS OF STRETCHING VIBRATIONAL ENERGY LEVELS OF THE CH3I MOLECULE BY A NONLINEAR MODEL

A nonlinear model, i.e. the quantized discrete self-trapping equation, is applied to calculate the highly excited CH stretching vibrational energy levels of the CH₃I molecule in the liquid phase at the electronic ground state up to n=8. The obtained results agree well with the experimental data and with those obtained from local mode model calculations. We note that the dominant feature of the methyl CH stretching vibrational energy levels of the CH₃I molecule is a pattern of local mode pairs. When n≥7, all the vibrational energy of the CH₃ group can nearly be localized on a single CH bond.     

Internal rotation in the spectrum of acetaldehyde

The geometrical structure of acetaldehyde from the microwave spectrum and torsional transitions from the far infrared spectrum have been fitted with a semirigid model in order to obtain the torsional parameters V″₃ = 415.0 and V″₆ = 22.3 cm^?1 and the torsional energy levels of the isotopic species CH₃CHO, CH₃CDO, CD₃CHO, and CD₃CDO. These have been used in fitting torsional sequences in the 182-nm system of the electronic spectra of these species to obtain the excited state parameters V′₃ = 880 and V′₆ = 77 cm^?1. Both the ground and excited state parameters are in good agreement with ab initio predictions.     

Theoretical study of the Ru + CH3F reaction

CASSCF-MRMP2 calculations have been performed to analyse the reaction of fluoromethane with a bare ruthenium atom. Potential energy curves emerging from the ground state and the first excited state of the reactants, Ru(⁵F, ³F;d⁷s¹) + CH₃F, were calculated for representative electronic states associated with different approaching modes of the fragments. Whereas no favourable channels correlating with the ground state asymptote were detected for the insertion of the ruthenium atom into the C–H bond of the methyl fluoride molecule, the oxidative addition of the C–F bond of this molecule to the metal atom along the reaction path evolving from the ground state of the fragments leads to the stable inserted product CH₃–Ru–F. Although forming less stable products, insertion of ruthenium into the C–H and C–F bonds of the fluorocarbon molecule can occur through electronic states which emerge from the excited triplet state asymptote.