Br2+分子离子[1+1]双光子解离动力学

本文利用最近研制的低温离子阱-离子速度成像谱仪在冷离子束中研究了同位素质量分辨的⁷⁹Br₂⁺分子离子的[1+1]双光子激光解离动力学. 借助其1⁴Σ^-_u,3/2态为中间态使⁷⁹Br₂⁺共振吸收两个光子至4∽5 eV区域的高激发态并发生解离. 利用离子速度成像技术获得了光解产物⁷⁹Br⁺的二维速度分布和平动能释放谱. 通过平动能释放谱确定了不同解离能量处量子态分辨的解离产物通道分支比. 光碎片产物的角分布表明⁷⁹Br₂⁺分子离子的双光子解离是1⁴Σ^-_u,3/2态的ΔΩ=0平行跃迁至一个Ω=3/2高解离态发生的. 由于分子激发态中的强自旋-轨道耦合作用，高激发的四重态很可能参与到实验观测的光解过程.     

异氰酸分子NH(a1Δ)+CO(X1Σ+)通道在193nm的离子成像光解动力学研究

The photodissociation dynamics of isocyanic acid (HNCO) has been studied by the timesliced velocity map ion imaging technique at 193 nm. The NH(a¹Δ) products were measured via (2+1) resonance enhanced multiphoton ionization. Images have been accumulated for the NH(a¹Δ) rotational states in the ground and vibrational excited state (v=0 and 1). The center-of-mass translational energy distribution derived from the NH(a¹Δ) images implies that the CO vibrational distributions are inverted for most of the measured ¹NH(v|j) internal states. The anisotropic product angular distribution observed indicates a rapid dissociation process for the N-C bond cleavage. A bimodal rotational state distribution of CO(v) has been observed, this result implies that isocyanic acid dissociates in the S₁ state in two different pathways.     

间氟溴苯分子240 nm紫外光解动力学

The photodissociation dynamics of m-bromofluorobenzene has been experimentally investigated at around 240 nm using the DC-slice velocity map imaging technique. The kinetic energy release spectra and the recoiling angular distributions of fragmented Br(²P_3/2) and Br(²P_1/2) atoms from photodissociation of m-bromofluorobenzene have been measured at different photolysis wavelengths around 240 nm. The experimental results indicate that two dissociation pathways via (pre-)dissociation of the two low-lying ¹ππ^* excited states dominate the production process of the ground state Br(²P_3/2) atoms. Because of the weak spin-orbit coupling effect among the low-lying triplet and singlet states, the spin-orbit excited Br(²P_1/2) atoms are mainly produced via singlet-triplet state coupling in the dissociation step. The similarity between the present results and that recently reported for o-bromofluorobenzene indicates that the substitution position of the fluorine atom does not significantly affect the UV photodissociation dynamics of bromofluorobenzenes.     

二氧化碳分子离子经由Ã2Πu1/2电子态振动能级共振的光解动力学：一项时间切片离子速度成像技术研究

We report on the photodissociation dynamics of CO₂⁺ via its òΠ_u,1/2 state using the scheme of [1+1] photon excitation that is intermediated by the mode-selected òΠ_u,1/2( u1,u2,0) vibronic states. Photodissociation fragment exciation spectrum and images of photofragment CO⁺ have been measured to obtain reaction dynamics parameters such as the available energy and the average translational energy. Combining with the potential energy functions of CO₂⁺, the dissociation mechanism of CO₂⁺ is discussed. The conformational variation of CO₂⁺ from linear to bent on the photodissociation dynamics of CO₂⁺ is verified.     

荧光色散谱对FeS(X5△)振动常数的实验确认

基于之前的激光诱导荧光激发谱工作,采用激光诱导荧光色散谱技术直接侦测中性FeS基电子态X5￠振动能级到v″=3而获得其振动常数. 所得FeS(X⁵△)振动频率值(518±5 cm^-1)和最近的光电子能谱测量值(520±30 cm^-1) [J. Phys. Chem. A 107, 2821 (2003)]符合得较好,该光电子能谱测量值是之前唯一报道的FeS电子态振动频率的实验值. 通过比较实验结果和相关文献(主要来自理论预测),确定FeS的基态是X⁵△态.     

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.     

烷烃类分子对NC0（A^2∑^＋）自由基的猝灭

采用激光光解—激光诱导荧光(LP—LIF)的方法，用266nm激光光解CHBr3分子产生CH自由基，再与N2O继续反应作为NCO自由基的产生源，用438．6nm激光将电子基态X^2∏i(00^10)的NCO激励到激发态A^2∑^+(00^00)上，通过检测激发态NCO时间分辨荧光信号，测得室温(298K)下NCO(A^2∑^+)被烷烃类分子猝灭的实验结果，获得了A^2∑^+(00^00)态猝灭速率常数．实验发现，随着烷烃分子中C—H键数增加，其猝灭截面也近线性增加，但随着分子体积增大，这种增加趋缓．     

C2（a 3Πu）+NO 的反应机理研究

在G2 (CC ,MP2 )理论水平上研究了C2 (a3 Πu)自由基与NO分子的反应 .计算了反应体系最低二重态势能面上各驻点的构型参数、振动频率和能量 ,揭示了此反应存在两种反应机理 :由NO中的O原子进攻C2 自由基形成CCON中间体的CCON机理和NO中的N进攻C2 自由基形成CCNO中间体的CCNO机理 ,分析了对应与这两种反应机理的五个可能的反应通道 ,得出了由NO中的N原子进攻3 C2 自由基 ,生成中间体CCNO自由基 ,最终得到产物CN +CO的通道是最有利的通道 .     

固态氢分子基质隔离高分辨光谱实验装置及其应用

建立了用傅立叶变换红外光谱和中红外差频激光光谱方法研究氢基质隔离光谱的测量装置. 作为装置的测试, 观测了3 cm长的固态氢分子晶体在1-5 μm波段的吸收光谱. 并用中红外差频激光测量其在2410 cm-1附近的W0(0)(v=0→0, J=6→0)谱线的高分辨精细结构. 通过在低温基片上喷溅沉积氢分子晶体薄膜的方法, 对氢基质隔离的CO2分子的高分辨红外吸收光谱进行了研究.     

Laser spectroscopy of jet－cooled CuF in visible region

The laser-induced fluorescence excitation spectra of jet-cooled CuF have been recorded in the range of 19000－21470cm^{-1}, in which the CuF radicals were produced by the reaction of SF_6 with copper atoms from a dc discharge-sputtering source under supersonic jet conditions. Eight observed vibronic transition bands have been assigned as the transition from the ground state X(^1Σ^+) to B(^1Σ^+), C(^1Π) and an unreported upper state. The rotational structure of all observed bands has been analysed at the estimated rotational temperature 80K. We determined the newly observed band to be the (^1Π, v=1)－X(^1Σ^+v=0) transition according to the character of the rotational structure and the isotopic shift analysis. In addition, the lifetimes of the states involved in these bands were measured.