H+CH3D→H2+CH2D反应的十维量子动力学研究

本文采用最近发展的十维含时波包方法研究了H+CH₃D→H₂+CH₂D反应的模式选择性,计算了反应物CH₃D在基态、CH₃对称和不对称伸缩振动激发态、CD伸缩振动激发态以及CH₃弯曲模式的基频和倍频激发态等6个初始状态下的反应几率. 计算结果表明,在碰撞能0.0∽1.0 eV区间内,激发CH₃的任意一种伸缩振动模都能增强反应活性,而CD伸缩振动激发对反应的促进作用不明显. CH₃弯曲振动模的基频激发对促进反应活性几乎没有影响,由于CH₃对称伸缩振动模的基频与CH₃弯曲振动模倍频之间的费米共振作用,CH₃弯曲振动模的倍频激发显著增强了反应活性.     

对典型多通道反应H+CH3OH的模式特异动力学研究

H+CH₃OH作为典型的多通道反应,在燃烧和星际中起着重要的作用. 本文基于在UCCSD(T)-F12a/AVTZ水平上计算的大量数据点,构建了该体系的全维精确势能面,并基于该势能面,研究了不同产物通道的模式特异动力学. 结果表明,O-H 伸缩、沿C-O轴的扭转以及C$-$H伸缩等模式的振动激发对H₂+CH₃O、H₂+CH₂OH、H₂O+CH₃和H+CH₃OH四个产物通道有着不同的影响. 该研究有助于理解具有多个产物通道的复杂反应的模式特异动力学,进而帮助控制其竞争反应.     

H+Br2→HBr+Br反应的态-态量子动力学研究

H原子与卤素气体(F₂,Cl₂,Br₂)的反应是典型的轻-重-重原子-双原子反应. 对于研究化学激光的基本反应途径十分重要. 之前所有的实验结果都表明,H+Br₂→HBr+Br反应的势垒高度很小,甚至是负值. 本文基于11698个UCCSD(T)/CBS水平的从头算能量点,用FI-NN方法构建了HBr₂体系的精确全维全域势能面,还包括了Br原子²P_3/2轨道的自旋-轨道耦合. 势能面有一个下沉的势垒(-0.351 kcal/mol}),放热(ΔH₀=-41.265 kcal/mol) 和实验值吻合的很好,在这个势能面上应用含时波包方法计算了H+Br₂→HBr+Br反应的态-态积分和微分截面. 对初始基态反应,产物HBr(v′=2,3,4)态在所考虑的整个能量范围内占主导地位,说明HBr是振动态布居反转的. 温度300 K时,计算的产物振动分布在$v$$''$=3有最大值,在v′=0,1的分布可以忽略不计,这与Setser及合作者和Polanyi及合作者的实验结果相一致. 超过一半的总可用能量进入到产物的内部运动中,这其中大部分进入到振动中. 计算表明,反应物Br₂的初始转动激发对产物振转态分布和微分截面影响很小,而初始振动激发则有一定影响. 在低能区域,初始振动激发到v₀=5态很明显的增强了产物的振动激发. 在初始基态和初始转动激发态下,碰撞能量到0.5 eV的微分截面在后向达到峰值,但随着碰撞能量的增加,角分布的宽度显著增加. 对于初始振动激发态,产物微分截面的结构较为复杂,对高振动激发态产物有很强的前向散射峰.     

OH+C2H3F的反应机理及产物支化比反应的理论研究

本文对HOC₂H₃F可能解离通道的势能面进行从头算CCSD(T)/CBS//B3LYP/6-311G(d，p)计算，同时对速率常数进行Rice-Ramsperger-Kassel-Marcus计算. 生成主要产物CH₂CHO+HF最有利的反应途径是OHC₂H₃F→i2→TS14→i6→TS9→i3→TS3→CH₂CHO+HF，其中速率决定步骤是HF通过TS11从CO桥接位置解离，能量比反应物高3.8 kcal/mol. 借助中间态TS14，F原子从C_α迁移到C_β位置生成CH₂O+CH₂F，然后通过中间态TS16，H从O迁移到C_α位置；通过中间态TS5，C-C键断裂生成产物，其能量比反应物低1.8 kcal/mol，比TS11低4.0 kcal/mol.     

CH2和CH3自由基吸附在Cun (n=1-6)团簇上C-H对称振动模式的软化

利用密度泛函理论中杂化泛函理论方法计算了CH₂和CH₃自由基吸附在Cu_n(n=1～6)团簇上时C?H对称伸缩振动模式的软化性质,结果表明,CH₂在Cun团簇上的吸附要比CH₃的吸附强. 计算得到的C-H键的振动频率与实验上测量的这两个自由基吸附在Cu(111)表面的结果符合得很好,随着团簇尺寸的增加,C-H对称伸缩振动频率的软化(红移)越来越大.     

OH+H2S→H2O+SH反应的模式特异性量子动力学研究

研究氢抽取反应OH+H₂S对于理解酸雨形成、空气污染和气候变化的原因具有重要意义. 本文在降维模型下使用量子含时波包方法研究了OH+H₂S→H₂O+SH反应的动力学行为. 研究表明，该反应在低碰撞能时表现出无垒反应的特征，而在高碰撞能下表现出具有显著势垒的激活反应的特征. 激发反应物H₂S分子的对称或反对称伸缩模式比激发弯曲模式更有效地促进了反应，该动力学特征可以通过各正则模式与反应坐标的耦合强度来解释. 此外，模式指定的反应速率常数表现出明显的非阿伦尼乌斯温度依赖性.     

Reaction of C2HCl2+O2: Combined TR-FTIR Spectroscopy and Electronic Structure

用时间分辨傅立叶变换红外发射光谱(TR-FTIR)和G3MP2//B3LYP/6-311G(d,p)水平的电子结构计算研究了环境化学中重要的二氯代乙烯自由基C₂HCl₂和O₂分子的基元反应通道和机理. 通过0.5 cm^-1高分辨的TR-FTIR发射光谱观察到三种振动激发态产物CO₂、CO和HCl,由光谱拟合得到CO和HCl的振动态分布,结合电子结构计算的反应势能曲线,提出反应机理和能量上最可能的反     

密度泛函理论研究α-MoC(100)在甲醇水蒸汽重整中的催化作用

本文通过密度泛函理论计算方法探究了α-MoC催化甲醇水蒸气重整(CH₃OH+H₂O→CO₂+3H₂)反应,系统地研究了甲醇水蒸气重整反应中相关中间体的吸附行为和基本步骤的动力学. 结果表明,在α-MoC(100)表面,甲醇容易裂解形成CH₃O中间体,CH₃O进一步脱氢为CH₂O. 通过比较CH₂O和OH缔合过程和CH₂O直接分解过程,发现CH₂O和OH之间更容易形成CH₂OOH而不是分解成CHO和H. 计算结果表明,CH₂OOH中间体的连续脱氢对CO₂有很高的选择性. 相反,在α-MoC(111)表面,由于CH₂O中间体的强吸附使其更偏向于脱氢生成CHO,最后生成产物CO. 此外,高水解离产生的OH物种可以促进中间体O-H键的断裂,并显著降低反应能垒. 本文不仅揭示了α-MoC(100)晶面在甲醇水蒸气重整反应中的催化作用,也为α-MoC基催化剂的设计提供了理论指导.     

F+H2O/D2O→HF+OH反应的准经典轨迹研究：能垒、反应物转动激发和同位素取代的影响 (cited: 4)

在新构建的含旋轨耦合校正的FH₂O基态势能面上,采用准经典轨迹方法详细研究了F+H₂O/D₂O→HF/DF+OH/OD的反应动态学．氢和氘抽取反应经过较低的类反应物过渡态直接发生反应,生成振动激发的HF/DF和内能较低的OH/OD产物．由于新构建的势能面能垒较低,得到的积分反应截面与实验值吻合．但新势能面对产物态分布和模式选择性影响较小．理论计算结果显示H2O的转动态激发对反应有很强的促进作用,说明其与反应坐标耦合紧密．     

CH3OH在ZnO(0001)表面的光催化解离

本文利用266 nm波长的激光及程序升温脱附的方法研究了甲醇在ZnO(0001)表面的光催化反应. TPD结果显示部分的CH₃OH以分子的形式吸附在ZnO(0001)表面,而另外一部分在表面发生了解离. 实验过程中探测到H₂,CH₃^·,H₂O,CO,CH₂O,CO₂和CH₃OH这些热反应产物. 紫外激光照射实验结果表明光照可以促进CH₃OH/CH₃O^·解离形成CH₂O,在程序升温或光照的过程中它又可以转变为HCOO^-. CH₂OH_Zn与OH_ad反应在Zn位点上形成H₂O分子. 升温或光照都能促进CH₃O^·转变为CH₃^·. 该研究对CH₃OH在ZnO(0001)表面的光催化反应机理提供了一个新的见解.     

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.     

Assignments of optically pumped CH3OD laser lines

Fifteen laser lines from CH₃OD pumped by a CO₂ laser are assigned to specific rotational energy transitions. These assignments have been obtained from the approximation that, except for one constant, the molecular constants in the excited CO stretching state are same as those in the ground state.     

乙醛光解动力学的离子速度成像

利用时间切片离子速度成像技术在275～321 nm能量范围内重新研究了乙醛自由基通道CH₃+HCO的光解动力学. 通过共振增强多光子电离的方法探测甲基碎片. 对甲基的伞形振动基态和激发态(v₂=0和1)进行了影像探测. 乙醛通过T₁电子态系间窜越到S₁电子态的解离产物具有很高的动能释放和很低的内能激发,碎片的振动能和转动能随激发能量的增加而增加. 乙醛T₁电子态的势垒高度经测量高于基电子态3.881±0.006 eV.     

Infrared and far-infrared spectroscopy of CH3OH: TeraHertz laser lines and assignments

We use a ¹³CO₂ laser as optical pumping source to search for new THz laser lines generated from ¹³CH₃OH. Nineteen new THz laser lines (also identified as far-infrared, FIR) ranging from 42.3 μm (7.1 THz) to 717.7 μm (0.42 THz) are reported. They are characterized in wavelength, offset, relative polarization, relative intensity, and optimum working pressure. We have assigned eight laser lines to specific rotational energy levels in the excited state associated with the C-O stretching mode.     

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.     

UH和UH2分子的结构与势能函数

用相对论有效原子实势(RECP)和密度泛函(B3LYP/SDD)方法研究了UH,UH₂基态和低激发态的结构和势能函数,导出了分子的光谱数据.结果表明,UH和UH₂的基电子状态分别为X⁴Π和X³A₂,离解能分别为2.886eV和5.249eV,UH₂具有C2v对称性,得到了UH和UH₂的几个不同的低激发态的结构与光谱数据.应用多体项展式理论以及数字拟合方法 关键词： UH 2')" href="#">UH₂ 势能函数 分子结构     

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.     

Calculation of interaction of the stretching and bending vibrations of HF in the hydrogen-bonded complex [F(HF)2]?

Vibrations of the [F(HF)₂]^? complex are calculated with allowance for the anharmonic interactions of the stretching vibrations of HF monomers and their rotations about the centers of gravity of HF in the plane of the complex. A four-dimensional vibrational Schr?dinger equation is solved using a potential energy surface calculated in the MP2/6-311++G(3df,3pd) approximation with the superposition of atomic functions of the monomers taken into account. The equilibrium and vibrationally averaged structures of the complex are determined. The frequencies and intensities for spectral transitions from the ground state to a number of excited vibrational states are calculated. It is shown that, due to resonances between the excited states of the stretching modes and doubly excited states of the bending modes, the overtone transitions associated with the bending modes borrow a significant part of the intensity of fundamental stretching transitions.     

The photodetachment spectrum of OHF−: the influence of vibration at a transition state

New ab initio potential energy functions for collinear OHF^? and OHF have been used with time-dependent wavepacket studies in a simulation of the photodetachment spectrum of the OHF^? anion. Franck—Condon excitation of OHF^? lies within the transition state region for the bimolecular reaction F + OH ? O + HF on the lowest triplet surface. The branching ratios for fragmentation of the excited OHF are such that the peaks in this spectrum may each be correlated with dissociation to a single vibrational state of the O + HF(v) or OH(v) + F products. The possible influence of vibrational excitation of the anion has been explored also. This is predicted to lead to marked changes in the spectra. Experimental observations of such spectra could be used in refinement of the potential as could an experiment in which the electron kinetic energy is detected in coincidence with the vibrational states of the molecular products or with the kinetic energy of the atomic products. The calculations revealed a number of metastable resonances on the OHF surface, although these are all at higher energies than are relevant to the photodetachment spectrum from the ground state anion.