势垒高度对Cl+H2(D2)反应的影响

使用三维含时波包方法在两个势能面上研究了Cl+H2(D2)反应．所使用的两个势能面都是从CW(Capecchi和Wener)势能面得到的，第一个是CW势能面的基态面加自旋轨道耦合修正，第二个是CW势能面的基态面没有自旋轨道耦合修正．在这两个势能面上得到了碰撞能从0.1到1.4 eV的积分截面以及反应几率．对于Cl与D2反应，考虑自旋轨道耦合后由于势垒高度的增加反应截面向高能处有一个平移，但Cl与H2反应在低能处的反应活性反而增大了，原因是虽然自旋轨道耦合效应增加了势垒高度，同时减小了势垒宽度，隧道效应更加明显，而隧道效应在低能处起着比较重要的作用，所以反应活性比较大．当碰撞能大于0.7 eV时，没有考虑自旋轨道耦合时势垒高度较低，因而反应活性较大．     

A study of the ground states of CaC2H2+,CaC2D2+ and CaC2H4+

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Spectral Diagnostics of the Dynamics of the Formation of a Homoconjugated Complex [HCN.H.NCH]+

Optics and Spectroscopy - A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH]+ linear complex along the profile of the proton...     

Interaction of Muons with H2/H3-Centres in Diamond

We report on transverse field muon spin rotation measurements on a nitrogen-rich type Ia diamond, both before and after the conversion of some of the aggregated nitrogen centres to nitrogen-vacancy complexes known as H2/H3-centres. The prompt fractions f and the spin relaxation rates λ were determined for the diamagnetic (μ_d) and the paramagnetic (Mu_T) states in the temperature range 10–300 K. The production of the nitrogen-vacancy complexes had little effect on the parameters of the Mu_T state for which f and λ remained unchanged at approximately 30% and 4 μs⁻¹, respectively. For the μ_d state, on the other hand, the formation of the H2/H3-centres resulted in an increase of the prompt fraction from 10(2)% to 20(3)%, and (for the first time) the spin relaxation rate showed a non-zero value of 0.020(3) μs⁻¹. These results show evidence of strong μ_d interactions with the nitrogen-vacancy complexes in diamond, and suggest a more complex structure for this state than a bare μ⁺. This revised version was published online in September 2006 with corrections to the Cover Date.     

H_2O_2胁迫下菠菜叶片延迟发光动力学过程的分析

从生物延迟发光的机理出发,建立了生物延迟发光动力学方程,发现菠菜叶片的延迟发光随时间按双指数规律衰减,表明菠菜叶片延迟发光来源于快项和慢项两个发光系统,其动力学行为可以通过发光动力学参数积分强度、初始光子数和衰变时间定量描述。用体积分数为10%的H2O2溶液处理菠菜叶片,随着处理时间的延长,延迟发光积分强度和初始光子数快速降低,积分强度和初始光子数的变化呈正相关,表征快相和慢相发光特征的两个衰变时间表现出逐渐减小的趋势。积分强度和初始光子数的变化代表了叶片的光合能力和代谢强度的下降,衰变时间的变化暗示H2O2可能对叶片PSⅡ中D1和D2两条多肽造成了破坏。     

用原子轨道强耦合方法研究H(1s)+H(2s)碰撞的反应截面

采用单电子的双中心原子轨道强耦合方法,计算了H(1s)+H(2s)碰撞体系H(2s)失去电子过程的总截面,并与前人的实验结果进行了比较.研究表明,采用双中心原子轨道强耦合方法得到的H(1s)+H(2s)体系H(2s)失去电子过程的截面与实验比较符合.同时,还给出了H(1s)+H(2s)碰撞体系H(2s)电离过程、H(1s)俘获电子过程和H(2s)退激发到H(1s)过程的理论截面.     

HAT HMBC: a hybrid of H2BC and HMBC overcoming shortcomings of both

A new 2D NMR experiment, HAT HMBC, that is a hybrid of H2BC and HMBC aims at establishing two-bond correlations absent in H2BC spectra because of vanishing (3)J(HH) coupling constants. The basic idea is to create an additional pi phase difference in the multiplet structure in HMBC peaks with respect to the (n+1)J(HH) coupling constant between the proton(s) attached to a (13)C and a (1)H separated by n bonds. Thus HMBC peaks associated with small J(HH) will be the most attenuated in a HAT HMBC spectrum in comparison to a regular HMBC spectrum, i.e. peaks associated with (n+1)J(HH) and (n)J(CH) will for n>2 usually be strongly attenuated. The HAT HMBC pulse sequences contain the same number of pulses as regular HMBC and are only a few milliseconds longer.     

Direct ab initio dynamics calculations of the reaction rate for the hydrogen abstraction reaction of NCO with CH4 and C2H6

The kinetics of the hydrogen abstraction reactions NCO + CH₄ (R1) and NCO + C₂H₆ (R2) have been studied over a wide temperature range. The minimum energy paths (MEPs) were calculated at the MP2/cc-pVDZ level and single-point calculations were refined at the G3MP2 level. The rate constants for the title reactions were calculated using canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) contributions. The fitted three-parameter formulae are k ₁ = 2.52 × 10^?22 T ^3.46 exp(2466/T) and k ₂ = 9.8 × 10^?22 T ^3.2 exp(411.8/T) cm³ molecule^?1 s^?1 for (R1) and (R2), respectively. The calculated rate constants were found to be in good agreement with the available experimental data. Deuterium kinetic isotope effects were also investigated. Both reactions show a significant kinetic isotope effect in the low-temperature range.     

一个灵敏测定过氧化氢的吖啶红共振散射光谱新方法

在pH为5.0的HAc-NaAc缓冲液中,Fe2 催化H2O2产生·OH,·OH氧化I-为I2.过量I-与I2反应生成的I-3,与吖啶红(AR)形成AR-I3缔合物分子.在疏水作用和分子间力作用下,AR-I3缔合物分子自动聚集形成(AR-I3)n缔合物微粒.该缔合物微粒在320,400,595 nm处产生3个共振散射峰.H2O2的浓度在0.50～16.0×10-6 mol·L-1范围内与400 nm波长的共振散射光强度成线性关系,方法的检出限为2.0×10-7 mol·L-1 H2O2,用于废水中H2O2的测定,结果满意,回收率在97.9%～101.2%之间.     

Theoretical study of the hydrogen abstraction reaction of CH3OH with NCO

A direct dynamics method is employed to study the mechanism and kinetics of the hydrogen abstraction reaction of CH₃OH with NCO. The optimized geometries and frequencies of the stationary points and the minimum-energy paths (MEPs) are obtained at the MP2/6-311G(d,p) level. In order to obtain more accurate potential energy surface (PES) information and provide more credible energy data for kinetic calculation, the single-point energies along the MEPs are further computed at QCISD(T)/6-311+G(d,p) and G3MP2 levels. The rate constants for two channels, the methyl-H abstraction channel and hydroxyl-H abstraction channel, are calculated by canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) contributions over the wide temperature region 220–1500?K. The theoretical overall rate constants are in good agreement with the available experimental data. For the title reaction, the methyl-H abstraction channel is dominant, while the hydroxyl-H abstraction channel is negligible over the whole temperature region.     

H2AT120 蛋白磷酸化致癌的动力学特性

基于Hill动力学与Michaelis-Menten方程,建立理论模型研究H2AT120组蛋白磷酸化促进癌症发生发展的动力学特性.研究发现,在H2AubK119-H2AT120D-H2AT120P信号通路中,VRK激酶(vaccinia-related kinase 1)在很大程度上调控H2AT120磷酸化的动力学. VRK过高或者过低表达,都会促使H2AT120磷酸化出现异常,导致基因的不恰当表达,致使细胞癌变发生.通过考察体系演化过程中的动力学稳定性,我们发现,H2AubK119、H2AT120D、H2AT120P随时间演化动力学出现Hopf分岔,表明了体系随时间演化动力学的转变特性,由此也表明了,H2AT120蛋白磷酸化促进癌症发生发展的复杂性.基于本文模型,我们解释了VRK、H2AubK119、H2AT120D对致癌的调控特性,进一步理解了H2AubK119-H2AT120D-H2AT120P信号回路的致癌作用机理.理论结果符合实验,揭示了H2AT120磷酸化导致表观遗传变异的一种致癌机理,可为设计阻止由H2AT120发生变异诱发的癌症提供理论依据.     

基于第一性原理计算H_2S、CO_2、CH_4在Fe-MoS_2上的吸附性能

在高含硫气藏开发中,伴随着CH_4的采出,H_2S和CO_2也不可避免的被采出.这两种气体会产生管道腐蚀和气体中毒等诸多不利影响.为了解决这一现实需要,从研究较为广泛的MoS_2材料入手,考虑了其掺杂结构中的吸附性能的变化,相关计算原理基于密度泛函数理论.主要计算了一种吸附式掺杂过渡金属原子Fe在MoS_2上的结构,同时也计算了H_2S,CO_2,CH_4气体在其表面的吸附能,电荷转移,电子密度差等相关参数.结果表明,CH_4对这种材料表现出不敏感的特性,而CO_2、H_2S均表现出吸附的性质,预测这种材料可能作为一种可使用的吸附材料,或是开发作为一种新型的气体预警材料.     

H2-O2(N2)混气着火过程非线性特性研究

本文采用基元反应模拟H2-O2(N2)混合气体的着火过程,得到了不同散热和不同燃料-氧化剂初始浓度比条件下着火临界曲线。结果表明: H2/O2摩尔比相同时,不同散热条件下的着火临界曲线非常相似,可近似看成同一曲线在第二区的“延伸线”上滑移。临界曲线第二区的P—T关系符合2k1=ks[Ms]。散热对着火极限的影响和着火延迟时间有密切关系,在临界曲线第二区延迟时间最小,导致散热对该区的影响最弱,从而使着火临界曲线非常相似。     

H2O分子OH键振动能谱的代数计算

用U(2)代数模型,对H2O分子OH键的高激发振动能谱进行了理论计算,并与其它模型的计算相比较,结果表明,代数模型能以较小的标准偏差描述这一分子OH键的振动能谱。     

H2O和HLi分子的双光子激发

用全相对论量子力学计算H2O和HLi的双光子偶极激发。为对比起见,同时用非相对论的对称匹配团族-组态相互作用法(SAC-CI)计算其单光子激发。对于无对称中心的H2O和HLi,符合相应群的对称选择原则。双光子跃迁几率一般比单光子跃迁的小3～5个数量级。在计算双光子偶极激发时,应采用同时包含了空间的对称性和时间反转对称性的全相对论。     

The isomerization of cytosine: Intramolecular hydrogen atom transfer mediated through formic acid

The catalytic ability of H₂O and HCOOH to facilitate the tautomerism of KA to KIt isomer has been studied. It is shown that the direct tautomerism (path A) is unlikely because of the high activation free energy, whereas the presence of H₂O and HCOOH (paths B and C) significantly contributes to decreasing the activation free energy. Meanwhile, the conventional transition state theory followed by Wigner tunneling correction is applied to estimate the rate constants. The rate constant with Wigner tunneling correction for direct tautomerization is obviously smaller than that of HCOOH‐mediated tautomerization, which is the most plausible mechanism. Finally, another important finding is that the ratio of reaction rates between direct tautomerism reaction and catalyst‐induced tautomerism increases with the increase of the catalyst concentration at a given temperature. The results of the present study demonstrate the feasibility of acid catalysis for DNA bases isomerization reaction that would otherwise be forbidden.     

甘氨酸与水分子间相互作用的理论研究

在密度泛函(DFT)B3LYP/6_311++G(3d,3p)水平,对中性甘氨酸的最小点结构Ip和H2O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了三个氢键极小结构A、C和E,其中结构A为最稳定结构,它是H2O与甘氨酸的羧基(-COOH)形成两个氢键的结构,具有C1对称性.分别采用密度泛函理论(DFT)和MP2方法,在6-311++G(3d,3p)水平,对结构A的结构和结合能进行了比较计算,得到结合能ΔEDFT为-41.88 kJ/mol,ΔEMP2为-40.34 kJ/mol.     

Primary 1H/2H isotope effect in the NMR chemical shift of HClO4 salts of 1,8‐bis(dimethylamino)naphthalene derivatives

The primary ¹H/²H isotope effect for a number of protonated naphthalene proton sponges (DMAN‐s) was measured and correlated with the δ(¹H) value and IR spectroscopic characteristics of the [NHN]⁺ hydrogen bonds. A particular role of the unusual anharmonicity expressed in the isotopic ratio ISR ? is discussed when the fundamental vibrational levels are close to the barrier top for proton/deuteron motion. Copyright © 2007 John Wiley & Sons, Ltd.     

强激光场中H2^＋离解行为的研究

在多电子态模型下，利用二阶劈裂传播子算法计算了Ｈ２＾＋在强激光场中的离散行为。结果发现在高频场时分子的多光子离散碎片是近对称的，而对于低频场，在所考虑的激光强度下Ｈ２＾＋是被隧道离散的，因而其离散碎片Ｈ＾＋分布是反对称的，另外，文中还探讨了三脉冲形状对分子离解几率、离解碎片动力学行为的影响。