A dynamical Lie algebraic mehtod for quantum reactive scattering

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基于量子波包方法的态-态分辨反应散射动力学计算

本文回顾了最近十几年利用量子波包方法研究气相分子反应散射动力学的工作进展,特别是在态-态分辨水平上的工作进展。比较详细地讨论了目前存在的利用量子波包方法计算态-态微分截面的几种方法。目前态-态分辨的波包动力学计算可以精确地预测三原子和四原子分子反应散射的各种信息,文章最后对几个典型的利用波包方法在态-态分辨水平上研究过的三原子和四原子反应散射体系做了讨论。     

Unimolecular reactions on formaldehyde S0 PES

The competitive unimolecular reactions of formaldehyde, H₂CO→H₂+CO; H₂CO→trans-HCOH and H₂CO→H+HCO, were comparatively studied under the direct dynamics formalism, using Density functional and ab initio levels of theory. In addition, the geometric isomerization trans-HCOH→cis-HCOH was evaluated. Calculated reaction path properties were used in the determination of Rice–Ramsperger–Kassel–Marcus microcanonical rate coefficients. The reaction dynamics was evaluated for each individual process based on the nuclear displacements in the reaction path and normal coordinate analysis. Our results found are in very good agreement with experimental barrier heights and quantum yields trends.     

基元化学反应态态动力学研究*

化学反应动力学是化学领域最基础的学科之一,量子态分辨的基元化学反应动力学在最为基本的原子与分子的层次上对化学反应的机制提供深刻的理解。该领域的科学家们通过精心设计的实验和高精度的理论计算,使得态态反应动力学在过去的半个多世纪中取得了长足的进步,实验和理论的相互结合极大地促进了我们对化学反应本质的认识。本文从实验研究的角度,通过对实验技术的发展和对H₂O光解离、H+H₂、F+H₂、Cl+H₂、OH+H₂、F+CH₄等具体实例的态态动力学研究的简介,概况介绍了过去二十年里态态化学反应动力学研究所取得的进展,希望借此为读者提供对化学反应动力学领域的一个概略认识。     

Transfer of F− in the reaction of SF 6 − with SOF4: Implications for SOF4 production in corona discharges

The temperature (T) and electric field-to-gas pressure (E/P) dependences of the rate coefficientk for the reaction SF ₆ ^– +SOF₄SOF ₅ ^– +SF₅ have been measured. ForT<270 K,k approaches a constant of 2.1×10^–9 cm³/s, and for 433>T>270 K,k decreases withT according tok (cm³/s)=0.124 exp [–3.3 lnT(K)]. ForE/Pk has a constant value of about 2.5×10^–10 cm³/s, and for 130 V/cm·torr>E/P>60 V/cm·torr, the rate is approximately given byk (cm³/s)7.0×10^–10 exp (–0.022E/P). The measured rate coefficient is used to estimate the influence of this reaction on SOF₄ production from negative, point-plane, glow-type corona discharges in gas mixtures containing SF₆ and at least trace amounts of O₂ and H₂O. A chemical kinetics model of the ion-drift region in the discharge gap is used to fit experimental data on SOF₄ yields assuming that the SF ₆ ^– +SOF₄ reaction is the predominant SOF₄ loss mechanism. It is found that the contribution of this reaction to SOF₄ destruction falls considerably below the estimated maximum effect assuming that SF ₆ ^– is the predominant charge carrier which reacts only with SOF₄. The results of this analysis suggest that SF ₆ ^– is efficiently deactivated by other reactions, and the influence of SF ₆ ^– +SOF₄ on SOF₄ production is not necessarily more significant than that of other slower secondary processes such as gas-phase hydrolysis.     

Absolute quantum yield measurements for the formation of oxygen atoms after UV laser excitation of SO2 at 222-4 nm

The dynamics of formation of oxygen atoms after UV photoexcitation of SO₂ in the gas-phase was studied by pulsed laser photolysis-laser-inducedfluorescence ‘pump-and-probe’ technique in a flow reactor. SO₂ at room-temperature was excited at the KrCl excimer laser wavelength (222.4 nm) and O(³P_j) photofragments were detected under collision-free conditions by vacuum ultraviolet laser-induced fluorescence. The use of narrow-band probe laser radiation, generated viaresonant third-order sum-difference frequency conversion of dye laser radiation in Krypton, allowed the measurement of the nascent O(³P_j=2,1,0) fine-structure state distribution:n _j=2/n_j=1/n_j=0 = (0.88 ± 0.02)/(0.10 ± 0.01)/(0.02 ± 0.01). Employing NO₂photolysis as a reference, a value of Φ₀(³P) = 0.13 ± 0.05 for the absolute O(³P) atom quantum yield was determined. The measured O(³P) quantum yield is compared with the results of earlier fluorescence quantum yield measurements. A suitable mechanism is suggested in which the dissociation proceeds via internal conversion from high rotational states of the initially excited SO₂(~C¹B₂ (1, 2, 2) vibronic level to nearby continuum states of the electronic ground state.     

化学反应散射共振态的实验检测与理论模拟

化学反应中的散射共振态（或称反应性共振）控制着化学反应的分支比、产物的态分布及空间分布等。反应性共振的实验检测分为间接法和直接法。从理论上,一是构造反应体系的势能面,从势能面过渡态的结构来研究散射共振态;二是计算态-态反应动力学,尤其是用寿命矩阵来研究散射共振态。本文介绍反应性散射共振态的实验检测及理论模拟方法,并对今后的发展动向作出展望。