气相中Sc+和Ti+与CS2反应的计算研究

以Sc⁺和Ti⁺与CS₂反应作为第一前过渡金属离子与CS₂反应的范例体系. 采用密度泛函(UB3LYP/6-311+G*)方法计算研究了Sc⁺和Ti⁺在基态和激发态与CS₂反应的反应机理. 全参数优化了反应势能面上各驻点的几何构型, 用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证. 计算了不同多重度下的反应交叉势能面. 确定了Sc⁺和Ti⁺与CS₂的反应为插入-消去反应, 找到了基态和激发态金属离子与CS₂反应的主要通道.     

气相离子-分子反应B2H3-+CS2——B2H3S-+CS的理论研究

用密度泛函方法B3LYP/6-311++G(d,p)和高级电子相关的偶合簇法CCSD(T)/6-311++G(d,p)研究了气相离子-分子反应B₂H₃^-+CS₂B₂H₃S^-+CS的机理.结果表明,B₂H₃最可能进攻CS₂中碳原子形成三元环中间体,随后通过氢迁移和最终消除CS的反应步骤形成硫原子转移产物H₃BBS^-+CS,反应大量放热且不需要活化能.B₂H₃直接对CS₂中硫原子进攻夺取硫原子的反应方式存在一定能垒阻碍.计算结果有助于深入了解B₂H₃,B₃H-6和B₄H₇^-等缺电子硼氢负离子的反应行为.     

CS21B2(1Σ+u)态预离解产物CS的振转布居研究

用一束波长为210.27 nm的激光将CS2分子激发至预离解态1 B2(1 Σ+u),用另一束激光通过激光诱导荧光(LIF)方法检测碎片CS,在250.5～286.5 nm获得了CS碎片A1 Π←X1 Σ+振转分辨的激发谱.通过对光谱强度的分析,获得了CS碎片v″=0～8的振动布居和v″=1,4～8振动态的转动布居.结果发现,碎片CS的振动布居呈双模结构,分别对应于CS2分子1 B2(1 Σ+u)态的两个解离通道,即CS(X1 Σ+,v″=0～9)+S(3PJ)和CS(X1 Σ+, v″=0～1)+S(1 B2).由此得到两个解离通道的分支比S(3PJ): S(1 B2)为5.6±1.2.与前人193 nm处的研究结果相比, 210.27 nm激发更有利于S(3PJ)通道的生成.此外,实验还发现CS的转动布居不满足热平衡分布,为两个Boltzmann分布的合成.     

气相中Y+活化CS2中的C—S键

以Y+与CS2反应作为第二行前过渡金属离子与CS2反应的范例体系. 采用密度泛函UB3LYP方法, 对于Y+采用Stuttgart 赝势基组, 对于CS2采用6-311+G(2d)基组, 计算研究了Y+离子在基态和激发态时与CS2气相反应的机理. 并用UCCSD(T)方法在相同的基组水平上对各驻点作了单点能量校正. 结果表明Y+离子与CS2的反应是插入-消去反应, 在反应过程中会发生系间窜越, 并且找到了两个势能面的能量最低交叉点.     

CS2 +( 2 Πg )的(1+1)光解离动力学研究

在气束条件下,利用483.2 nm的激光(3+1)共振增强多光子电离(REMPI)CS2分子以产生CS2+离子源,用另一束可调谐激光在424～482 nm内,通过对CS2+( 2 Πg)(1+1)双光子共振解离产生的碎片离子激发谱的探测,来获取CS2+ 的光解离动力学信息.光解离碎片S+的激发谱 (PHOFEX)可归属为CS2+ ( 2 Πu,3/2 (v′=0～4, v′=v1′+ (1/2)v2′) ← 2 Πg,3/2 (0,0,0))和 ( 2 Πu,1/2(v′=0～4)← 2 Πg,1/2(0,0,0))的跃迁.对CS2+光解离动力学的研究表明,其产生S+的通道为:(i)CS2+吸收一个光子从基态 2 Πg共振激发至 2 Πu态,(ii)已布居的 2 Πu态的振动能级和 2 Πg态的高振动能级产生耦合, (iii)吸收第二个光子从上述耦合的振动能级进一步激发至 2 Σu +态,再通过 2 Σu +态与4Σ- 态间的自旋-轨道相互作用,经由4Σ- 排斥态解离产生S++CS.     

Photodissociation of CS2+( 2 Πg) via (1+1) Excitation

Photodissociation dynamics of CS2+molecular ions has been investigated by (1+two-photon resonance technique. CS2+were prepared by (3+1) resonance-enhanced multi-photon ionization (REMPI) of CS2molecules at 483. 2nm. The photofragment S+excitati (PHOFEX) spectra were recorded by scanning another laser in the 424~482nm region, and we assigned essentially to CS2+(~A2Πu,3/2(v′=0~4)←~X2Πg,3/2(0,0,0)) and (~A2Πu,1/2(v′=0,4)←~X2Πg,1/2(0,0,0)) (herev′=v1′+(1/2)v2′) transitions. The S+production channel wpreliminarily attributed to, (i) one-photon excitation CS2+from the ground state~X2Πgto texcited state~A2Πu; (ii) vibronic coupling between the~A2Πustate and the high vibrational lev in the~X2Πgstate; (iii) second photon excitation from the coupling vibrational levels to the excied state~B2Σu+and dissociation to produce S++ CS via the repulsive4Σ-state through spin-orb interaction between the~B2Σu+and4Σ-states.     

CS2+离子 C2Σg+←B2Σu+跃迁的Franck-Condon因子计算以及与光解离谱的比较

将线性三原子分子离子CS2+的对称伸缩振动简化为SC和S之间的简谐振动, 用谐振子的势能曲线和波函数对CS2+分子离子 C2Σg+和 B2Σu+电子态(对称伸缩)振动能级间跃迁的Franck-Condon因子进行了计算, 得到的结果与 C2Σg+←B2Σu+跃迁的光解离谱实验强度进行了比较, 对前人给出的分子数据(转动常数、分子平衡核间距)进行了验证和分析, 讨论了经由 C2Σg+←B2Σu+电子态振动能级间跃迁的光解离机理.     

CS2 分子 1 B2(1 Σ+u )态预解离动力学研究

The predissociation dynamics of CS2 at the g vibrational level of the 1B2(1Σu+) state has been studied, by measuring the predissociation lifetimes from the photofragment CS excitation (PHOFEX) spectrum and the ro vibrational populations of CS fragment from the laser induced fluorescence(LIF) spectrum. It is found that the angular momentum quantum number K of the g level accelerates the dissociation speed of CS2 at the 1B2(1Σu+) state, and increases the branching ratio of S(1D2)/S(3PJ) for the two dissociation channels, CS(X 1Σ+)+S(1D2) and CS(X 1Σ+)+S(3PJ). The dissociation mechanism was discussed based upon the observations.     

Theoretical studies of the reactions of M+ (M = Ta,W, Re) with CS2

Gas-phase CS₂ activation by M⁺ (M = Ta, W, Re) was studied by the B3LYP density functional method.The geometries for reactants, transition states, and products were completely optimized. CS₂ activation mediated by M⁺ (M = Ta, W, Re) were found to be a spin-forbidden process as a result of the crossing among the multistate energetic profiles. On the basis of the Hammond postulate, this was a typical two-state reactivity reaction. Among the different potential energy surfaces, the crossing points had been explored. The spin–orbit coupling (SOC) was also calculated between the electronic states of different multiplicities at the crossing point to estimate the intersystem crossing probability. For CP1, CP2, and CP4, the computed SOC constants were 80.28, 128.65, and 526.77 cm^?1, which obtained by using one-electron spin–orbit Hamiltonian in Gaussian 09.     

Effect of Vibrational Angular Momentum on the Lifetime of CS21B2(1Σ)State

Predissociation lifetimes of totally 13 vibrational levels in the 1B2 state of jet-cooled CS2 have been determined by simulating the rotational band contours of the PHOFEX spectrum in the range of 209. 5 ～ 216 nm, where the PHOFEX spectrum was obtained by monitoring the laser-induced fluorescence of CS fragment via the Q band head excitation of（A 1Π,v' = 0）&（X 1Σ + ,v" = 0）transition. In order to investigate the influence of vibrational angular momentum quantum number K of the excited 1B2 （ 1Σ + U ）state,the nozzle was heated to increase the hot-band transition intensities. The results indicate that,for levels with the same vibrational quantum number but different K numbers in the 1B2 （ 1Σ + u ）state of CS2 ,the lifetime decreases with the increasing of quantum number K, suggesting that the dissociation could be accelerated by K number.     

Study on the photodissociation spectra of CS2+ via B2Sigma u+ and C2Sigma g+ electronic states

The photodissociation spectra of CS(2)(+) ions via B(2)Sigma(u)(+) and C(2)Sigma(g)(+) electronic states have been studied by using two-photon excitation, where the parent CS(2)(+) ions were prepared by [3 + 1] REMPI (resonance-enhanced multiphoton ionization) at 483.2 nm from the jet-cooled CS(2) molecules. The [1 + 1] photodissociation spectrum of CS(2)(+) via the B(2)Sigma(u)(+)(upsilon(1)upsilon(2)0) <-- X(2)Pi(g,3/2)(000) transition was obtained by scanning the dissociation laser in the wavelength range of 270-285 nm and detecting the signal of both S(+) and CS(+). The [1 + 1'] photodissociation spectra of CS(2)(+) were obtained by fixing the first dissociation laser at 281.94 or 277.15 nm to excite the B(2)Sigma(u)(+) (000 or 100) <-- X(2)Pi(g,3/2)(000) transitions and scanning the second dissociation laser in the range of 606-763 nm to excite C(2)Sigma(g)(+)(upsilon(1)upsilon(2)0) <-- B(2)Sigma(u)(+)(000,100) transitions. New spectroscopic constants of nu(1) = 666.2 +/- 2.5 cm(-1), nu(2) = 363.2 +/- 1.9 cm(-1), chi(11) = -5.5 +/- 0.1 cm(-1), chi(22) = 1.6 +/- 0.1 cm(-1), chi(12) = -8.6 +/- 0.2 cm(-1), and k(122) = 44.9 +/- 2.5 cm(-1) (Fermi resonance constant) for the C(2)Sigma(g)(+) state are deduced from the [1 + 1'] photodissociation spectra. On the basis of the [1 + 1] and [1 + 1'] photodissociation spectra, the wavelength and level dependence of the product branching ratios CS(+)/S(+) has been found and the dissociation dynamics of CS(2)(+) ions via B(2)Sigma(u)(+) and C(2)Sigma(g)(+) electronic states are discussed.     

563～660 nm波段SO2+的PHOFEX连续谱

在超声分子束条件下,利用380.85 nm的电离激光使SO2分子经由[3+1]共振增强多光子电离(REMPI)产生纯净的SO2+(X 2A1)分子离子,用另一束解离激光在可见光波长区(563～660 nm)扫描获得了光解碎片SO+的激发(PHOFEX)谱.从563～660 nm波长区SO+的无结构连续谱以及SO2+解离的效率随波长增加而减少的实验事实,提供了SO2+(E,D,C)电子态附近存在α2A2对称性排斥态的证据,分析了产生SO+的[1+1]光解机理:(1)SO2+(X2A1)首先经由单光子激发到达B2B2中间态的密集能级区;(2)吸收另一个光子到达SO2+(E,D,C)电子态附近的α2A2排斥态,经由α2A2排斥态产生了到SO+(X2∏)+O(3Pg)的直接解离.     

气相CBr2 自由基的产生及激光诱导荧光色散谱研究

利用双层流动反应管作为束源,研究了F与CH2Br2反应生成的CBr2和Br2的气相激光诱导荧光色散谱,将得到的谱线分别指定为CBr2的(0,13,0)→(0,v2″,0)(v2″=1～6)跃迁和Br2的 3Π+u→ 1Σ+g跃迁,从光谱中首次得到气相CBr2自由基基态弯曲振动频率ν2″=215 cm-1,实验确认了CBr2自由基和Br2是F+CH2Br2过程多步反应的产物.     

1 + 1] photodissociation of CS(2)(+)(X̃2Π(g)) via the vibrationally mediated B̃2Σ(u)+ state: multichannels exhibiting and mode specific dynamics

Dissociation dynamics of CS(2)(+) vibrationally mediated via its B?(2)Σ(u)(+) state, was studied using the time-sliced velocity map imaging technique. The parent CS(2)(+) cation was prepared in its X?(2)Π(g) ground state through a [3 + 1] resonance enhanced multiphoton ionization process, via the 4pσ(3)Π(u) intermediate Rydberg state of neutral CS(2) molecule at 483.14 nm. CS(2)(+)(X?(2)Π(g)) was dissociated by a [1?+?1] photoexcitation mediated via the vibrationally selected B? state over a wavelength range of 267-283 nm. At these wavelengths the C?(2)Σ(g)(+) and D?(2)Σ(u)(+) states are excited, followed by numerous S(+) and CS(+) dissociation channels. The S(+) channels specified as three distinct regions were shown with vibrationally resolved structures, in contrast to the less-resolved structures being presented in the CS(+) channels. The average translational energy releases were obtained, and the S(+)∕CS(+) branching ratios with mode specificity were measured. Two types of dissociation mechanisms are proposed. One mechanism is the direct coupling of the C? and D? states with the repulsive satellite states leading to the fast photofragmentation. The other mechanism is the internal conversion of the C? and D? states to the B? state, followed by the slow fragmentation occurred via the coupling with the repulsive satellite states.     

Optical study of diffuse bi-directional nanosecond pulsed dielectric barrier discharge in nitrogen

In this study, a bi-directional high voltage pulse with 20 ns rising time is employed to generate diffuse glow-like dielectric barrier discharge plasma with very low gas temperature in N2 using needle-plate electrode configuration at atmospheric pressure. Both the diffuse nanosecond pulsed dielectric barrier discharge images and the optical emission spectra of the discharge are recorded successfully under severe electromagnetic interference. The effects of pulse peak voltage, pulse repetition rate, and the concentrations of Ar and O2 on the emission intensities of NO (A2Σ→X2Π), OH (A2Σ→X2Π, 0-0), N2 (C3Πu→B3Πg, 0-0, 337.1 nm), and N2+ (B2Σu+→X2Σg+, 0-0, 391.4 nm) are investigated. The effects of the concentrations of Ar and O2 on the discharge diffuse performance are also studied. It is found that the emission intensities of NO (A2Σ→X2Π), OH (A2Σ→X2Π, 0-0), N2 (C3Πu→B3Πg, 0-0, 337.1 nm), and N2+ (B2Σu+→X2Σg+, 0-0, 391.4 nm) rise with increasing pulse peak voltage, pulse repetition rate, and the concentration of Ar, but decrease with increasing the concentration of O2. The main physicochemical processes involved are also discussed.     

Steric effect in the energy transfer reaction of oriented CO (a 3Π, v'=0, Ω=1 and 2) + NO (X 2Π) → NO (A 2Σ+, B 2Π) + CO (X 1Σ+)

The oriented CO (a (3)Π, v' = 0, Ω = 1 and 2) beam has been prepared by using an electric hexapole and applied to the energy transfer reaction of CO (a (3)Π, v' = 0, Ω = 1 and 2) + NO (X (2)Π) → NO (A (2)Σ(+), B (2)Π) + CO (X (1)Σ(+)). The emission spectra of NO (A (2)Σ(+), B(2)Π) have been measured at three orientation configurations (C-end, O-end, random). The shape of the emission spectra (and/or the internal excitation of products) turns out to be insensitive to the molecular orientation. The vibrational distributions of NO (A (2)Σ(+), v' = 0-2) and NO (B (2)Π, v' = 0-2) are determined to be N(v'=0):N(v'=1):N(v'=2) = 1:0.40 ± 0.05:0.10 ± 0.05 and N(v'=0):N(v'=1):N(v'= 2) = 1:0.6 ± 0.1:0.7 ± 0.1, respectively, and the branching ratio γ/β [=NO (A (2)Σ(+))/NO (B (2)Π)] is estimated to be γ/β ～ 0.3 ± 0.1 by means of spectral simulation. These vibrational distributions of NO (A, B) can be essentially attributed to the product-pair correlations between CO (X, v″) and NO (A (2)Σ(+), v' = 0-2), NO (B (2)Π, v' = 0-2) due to energetic restriction under the vibrational distribution of CO (X, v″) produced from the vertical transition of CO (a (3)Π, v' = 0) → CO (X, v″) in the course of energy transfer. The steric opacity function has been determined at two wavelength regions: 220 < λ < 290 nm [NO (A → X) is dominant]; 320 < λ < 400 nm [NO (B → X) is dominant]. For both channels NO (A (2)Σ(+), B(2)Π), a significant CO (a (3)Π) alignment effect is recognized; the largest reactivity at the sideways direction with the small reactivity at the molecular axis direction is observed. These CO (a (3)Π) alignment effects can be essentially attributed to the steric asymmetry on two sets of molecular orbital overlap, [CO (2π) + NO (6σ (2π))] and [CO (5σ) + NO (1π (2π))]. All experimental observations support the electron exchange mechanism that is operative through the formation of a weakly bound complex OCNO.