超声射流下12C16O+离子A2Π1/2,3/2←X2Σ+激光诱导荧光激发谱

用一束波长为230.1nm的激光,通过(2 1)共振增强多光子电离(REMPI)过程激发超声射流冷却的CO分子制备处于基电子态X2Σ 的CO ,随后引入另一束可调谐激光将CO 离子激发至A2Π1/2,3/2态,利用光电倍增管(PMT)检测发射的荧光信号强度随激发光波长的变化,分别在487-493nm和453-459nm波长范围内获得了CO 离子A2Π1/2,3/2←X2Σ 电子态跃迁(0,0)和(1,0)带的激光诱导荧光(LIF)激发谱.     

OCS+经由A2Π←X2Π激发的光解离光谱

在超声分子束条件下,由423、420、412.2和408.4 nm的电离激光使OCS分子通过[3+1]共振增强多光子电离(REMPI)制备出OCs+ (X2Π)离子后,在260-325 nm范围内扫描解离激光获得了OCS+离子经由A2Π3/2←X2Π3/2 (000)和A2Π1/2←X2Π1/2 (000,001)跃迁的分质量光解离谱(母体离子OCS+的凹陷谱和碎片离子S+的增强谱).其中A2Π1/2←X2Π1/2 (001)跃迁的光解离谱是首次观察到.A2Π3/2←X2Π3/2(000)光解离谱得到了A2Π3/2电子态的光谱常数T0=31411.3 cm-1,v1=814.3 cm-1;由A2Π1/2←X2Π1/2 (000)光解离谱得到了A2Π1/2电子态的光谱常数v1=816 cm-1,v2=(380.4±2.8) cm-1,v3=(2052.7±5.1) cm-1,而从A2Π1/2←X2Π1/2 (001)光解离谱拟合出的A2Π1/2电子态的V1 (786.4 cm-1)稍有不同,表明在A2Π1/2←X2Π1/2(001)跃迁中A2Π1/2电子态的C-O键振动(V3)激发影响了A2Π1/2电子态C-S键的振动(V1).实验结果表明:在A2Π1/2←X2Π1/2(000,001)跃迁的光解离谱中能够显著观察到属于A2Π电子态的V2弯曲振动模激发的谱峰,例如A2Π1/2(020,120,021,…),而在A2Π1/2(v1v2v3)←A2Π3/2(000)跃迁的光解离谱中几乎没有观察到属于V2弯曲振动模激发的谱峰.这种弯曲振动激发和A2Π电子态的旋轨分裂分量(Ω)的相关性可以通过A2Π电子态的Fermi共振和Renner-Teller效应来解释.     

OCS+经由A2П←X2П激发的光解离光谱

在超声分子束条件下,由423、420、412.2和408.4nm的电离激光使OCS分子通过[3+1]共振增强多光子电离(REMPI)制备出OCS+(X2Π)离子后,在260-325nm范围内扫描解离激光获得了OCS+离子经由A2Π3/2←X2Π3/2(000)和A2Π1/2←X2Π1/2(000,001)跃迁的分质量光解离谱(母体离子OCS+的凹陷谱和碎片离子S+的增强谱).其中A2Π1/2←X2Π1/2(001)跃迁的光解离谱是首次观察到.由A2Π3/2←X2Π3/2(000)光解离谱得到了A2Π3/2电子态的光谱常数T0=31411.3cm-1,ν1=814.3cm-1;由A2Π1/2←X2Π1/2(000)光解离谱得到了A2Π1/2电子态的光谱常数ν1=816cm-1,ν2=(380.4±2.8)cm-1,ν3=(2052.7±5.1)cm-1,而从A2Π1/2←X2Π1/2(001)光解离谱拟合出的A2Π1/2电子态的ν1(786.4cm-1)稍有不同,表明在A2Π1/2←X2Π1/2(001)跃迁中X2П1/2电子态的C-O键振动(ν3)激发影响了A2Π1/2电子态C-S键的振动(ν1).实验结果表明:在A2Π1/2←X2Π1/2(000,001)跃迁的光解离谱中能够显著观察到属于A2Π电子态的ν2弯曲振动模激发的谱峰,例如A2Π1/2(020,120,021,…),而在A2П3/2(υ1υ2υ3)←X2Π3/2(000)跃迁的光解离谱中几乎没有观察到属于ν2弯曲振动模激发的谱峰.这种弯曲振动激发和A2П电子态的旋轨分裂分量(Ω)的相关性可以通过A2Π电子态的Fermi共振和Renner-Teller效应来解释.     

BF分子X1∑+,A1∏和B1∑+电子态的势能函数

使用SAC/SAC-CI和D95++,6-311++g,6-311++g**及D95(d)基组,分别对BF分子的基态X1∑+、第一简并激发态A1∏和第二激发态B1∑+的平衡结构和谐振频率进行优化计算.对所有计算结果进行比较,得出6-311++g**基组为最优基组.运用6-311++g**基组和SAC方法对基态X1∑+,SAC-CI方法对激发态A1∏和B1∑+进行单点能扫描计算,并用正规方程组拟合Murrell-Sorbie函数,得到相应电子态的势能函数解析式,由得到的势能函数计算了与X1∑+,A1∏和B1∑+态相对应的光谱常数,结果与实验数据较为一致.     

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.     

气相中2Sr+和2Ba+催化N2O与CO还原反应的理论研究

用密度泛函理论DFT-UB3LYP方法,对2Sr+,2Ba+采用相对论校正赝势基组SDD,对C,N,O采用6-311+G(2d)基组,计算研究了气相中碱土金属离子2Sr+,2Ba+催化N2O(X1∑+)+CI(X1∑+)→N2(X1∑+g)+CO2(X1∑+g)反应的微观机理.优化了二重态势能面上各反应物、中间体和过渡...     

N_2O~+经由B~2П_i←X~2П跃迁的光解离机理研究

在超声分子束条件下,利用360.50 nm的电离激光使N2O分子经由[3+1]共振增强多光子电离(REMPI)产生纯净的N2O+(X2Π(000))分子离子,用另一束解离激光在230-275 nm范围扫描获得N2O+经由B2Πi←X2Π跃迁产生的光解碎片(NO+和N2+)激发(PHOFEX)谱.获得的光解碎片激发谱可以归属为B2Πi(00n)←X2Π(000)序列跃迁.我们分别将线性三原子分子离子N2O+中N―N伸缩振动简化成NO和N之间的简谐振动,N―O伸缩振动简化成N2和O之间的简谐振动,用谐振子的简谐势能曲线和波函数对N2O+分子离子X2Π和B2Πi电子态振动能级间跃迁的Franck-Condon因子进行计算,和实验得到的碎片离子增强谱实验强度进行比较,对前人给出的分子数据(分子平衡核间距)进行验证,讨论了N2O+经由B2Πi(00n)←X2Π(000)电子态跃迁的光解离机理和碎片离子的分支比.     

N2O+离子B2П态的光谱与光解离动力学

用一束波长为360.55 nm的激光直接作用于超声射流的N₂O分子束, 通过(3+1)共振增强多光子电离(REMPI)过程制备纯净的N₂O⁺(X²П(0,0,0))母体离子, 再用另一束波长在243-278 nm范围的激光将母体离子激发至B²П态后解离. 扫描解离激光波长, 监测NO⁺离子碎片的强度, 从而获得N₂O⁺离子B²П态的光致碎片激发(PHOFEX)谱. 通过拟合转动分辨光谱, 得到了相应的转动常数和自旋分裂常数, 从而区分了A²Σ⁺态高振动能级和B²П态带源的贡献, 明确了N₂O⁺离子B²П态的光谱"带头"位置(37154 cm^-1), 并将获得的振动光谱初步归属为B²П(v₁,v₂,v₃)←X²П的振动跃迁序列. 通过对NO⁺碎片离子的飞行时间质谱峰形的分析, 还获得了解离过程中释放的平均平动能, 并结合电子激发态势能面, 讨论了N₂O⁺离子B²П态的解离机理.     

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.     

表面活性剂对Ag~+-H_2QS-K_2S_2O_8荧光体系的增敏作用及其分析应用

在弱碱性(pH10)介质中桂皮酸盐可以增加Ag~+_-H_2QS-K_2S_2O_8体系的荧光强度。其最大激发和发射波长分别为325nm和420nm,当Ag~+浓度在2～40μgL~(-1)范围内时,荧光强度与之成良好的线性关系。共存重金属离子的影响可用EDTA型阴离子交换柱除去。据此拟定的分析程序用于废水分析结果良好。     

碘甲烷通过Ã态和C态的多光子电离

碘甲烷分子与激光相互作用,发生的光解、激发电离等化学或物理过程已由许多人进行过研究.本文报导用多光子电离飞行质谱和光电子能谱技术研究碘甲烷通过(?)态和(?)态的多光子过程的主要实验结果和结论.实验用Nd:YAG 激光器泵浦染料激光器,可调谐的染料(R590)激光经倍频或与YAG 基频1.06μm 混频后分别得到280nm 或366nm 附近的紫外光,能量为0.2—2mJ/脉冲,时间脉     

CH自由基共振增强多光子电离光谱

ＣＨ自由基在燃烧化学、星际化学、化学发光和化学激光研究中占有重要的地位,并且作为最简单的碳氢化合物,ＣＨ自由基是理想的理论计算模型分子,在理论研究领域中也有着重要的地位．因此 ,多年来人们对ＣＨ自由基进行了大量的研究［１ -９］,但是对于ＣＨ自由基,到目前为止大部分局限于低激发态的研究,对于较高激发态的研究报导则很少见．Ｃｈｕｐｋａ等［２ -６］用(２ １)ＲＥＭＰＩ方法获得了ＣＨＤ态的ｖ＝２振动能级光谱．然而后来Ｔｊｏｓｓｅｍ和Ｓｍｙｔｈ［７］测量了同波段的ＲＥＭＰＩ光谱,发现他们测得的光谱谱峰强度与…     

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.     

The visible spectrum of zirconium dioxide, ZrO2

The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO(2), has been investigated using laser induced fluorescence (LIF) in the region from 17,000 cm(-1) to 18,800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17,000 cm(-1)-21,000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the A?(1)B(2)(ν(1), ν(2), ν(3)) ← X?(1)A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the X?(1)A(1) state of ω(1) = 898(1) cm(-1), ω(2) = 287(2) cm(-1), and ω(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the A?(1)B(2) state of T(e) = 16,307(8) cm(-1), ω(1) = 819(3) cm(-1), ω(2) = 149(3) cm(-1), and ω(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the A?(1)B(2) and X?(1)A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO(2) is made.     

Photodissociation dynamics of CBr4 at 267 nm by means of ion velocity imaging

The photodissociation dynamics of CBr4 at 267 nm has been studied using time of flight (TOF) mass spectrometry and ion velocity imaging techniques. The photochemical products are detected with resonance enhanced multiphoton ionization (REMPI) as well as single-photon vacuum ultraviolet ionization at 118 nm. REMPI at 266.65 and 266.71 nm was used to detect the ground Br(2P32) and spin-orbit excited Br(2P12) atoms, respectively. The translational energy and angular distributions are consistent with direct dissociation from an excited triplet state and indirect dissociation from high vibrational levels on the singlet ground state surface. Br2+ ions are also observed in the TOF spectra with a focused 267 nm laser. The counter fragment, CBr2+, is observed when this photolysis laser is unfocused, and photons at 118 nm are used to ionize the radical products. The translational energy distributions of the CBr2+ and Br2+ products can be momentum matched, which indicates that molecular Br2 elimination is one of the primary dissociation channels.     

用质谱和光电子能谱研究飞秒强场中的电离动力学

报导了用自制飞秒激光器通过飞秒多光子电离质谱和光电子能谱对飞秒强激光场与分子（氨、苯）相互作用的研究。飞秒激光脉宽约100fs,二倍频中心波长407.5nm,聚焦后脉冲功率密度达到1012W/cm2。氨的光电子能谱显示了（2+2）REMPI和（2+2）+1ATI、（2+2）+2ATI三组电子峰,每组峰又包括伸缩振动v1的带系,ATI峰的振动布居出现反转。随着光强增加,谱峰加宽而且振动能级出现平移。这些强场效应可用PonderomotivePotential解释。苯的飞秒质谱图与纳秒情况不同,分子离子为主,碎片峰很少。     

Multiphoton dissociation dynamics of BrCl and the BrCl+ cation

Ion imaging methods have enabled identification of three mechanisms by which (79)Br(+) and (35)Cl(+) fragment ions are formed following one-color multiphoton excitation of BrCl molecules in the wavelength range 324.6 > lambda > 311.7 nm. Two-photon excitation within this range populates selected vibrational levels (v'= 0-5) of the [X (2)Pi(1/2)]5ssigma Rydberg state. Absorption of a third photon results in branching between (i) photoionization (i.e. removal of the Rydberg electron-a traditional 2 + 1 REMPI process) and (ii)pi*<--pi excitation within the core, resulting in formation of one or more super-excited states with Omega= 1 and configuration [A (2)Pi(1/2)]5ssigma. The fate of the latter states involves a further branching. They can autoionize (yielding BrCl(+)(X (2)Pi) ions in a wider range of v(+) states than formed by direct 2 + 1 REMPI). Further, one-photon absorption by the parent ions resulting from direct ionization or autoionization leads to formation of Br(+) and (energy permitting) Cl(+) fragment ions. Alternatively, the super-excited molecules can fragment to neutral atoms, one of which is in a Rydberg state. Complementary ab initio calculations lead to the conclusion that the observed [Cl**[(3)P(J)]4s + Br/Br*] products result from direct dissociation of the photo-prepared super-excited states, whereas [Br**[(3)P(J)]5p + Cl/Cl*] product formation involves interaction between the [A (2)Pi(1/2)]5ssigma and [X (2)Pi(1/2)]5psigma Rydberg potentials at extended Br-Cl bond lengths. Absorption of one further photon by the resulting Br** and Cl** Rydberg atoms leads to their ionization, and thus their appearance in the Br(+) and Cl(+) fragment ion images.     

Photofragment Imaging of HNCO Decomposition at 210 nm: the Primary NH(a1￠)+CO(X1§+) Channel

The photodissociation of isocyanic acid (HNCO) on the ˉrst excited singlet state following the excitation at 210 nm was investigated with an ion velocity slice imaging technique by probing the CO fragment. It was found from the (2+1) resonance-enhanced multi-photon ionization (REMPI) spectrum that the CO fragments are rotationally hot with population up to Jmax=50. The velocity imagings of the CO fragments at JCO=30 and 35 indicate that formation of NH(a1￠)+CO(X1§+, v=0) is the predominant dissociation channel at 210 nm. From analysis of the CO fragment translational energy distributions, the NH(a1￠) fragment was observed to be rotationally cold, about half of the available energy was partitioned into the translational motion of fragments after dissociation, and the NH(a1￠)+CO(X1§+) dissociation threshold was determined at 42738§30 cm?1. From analysis of the CO fragment angular distributions, the dissociationanisotropy parameter ˉ was found to be negative, and increasing with the rotational quantum number of the NH fragment, i.e., from ?0.75 at JNH=2-4 to ?0.17 at JNH=11. Impulsive direct and vertical dissociation process of HNCO on the singlet state at 210 nm was conˉrmed experimentally. A classical impact dissociation model was employed to explain the dependence of the ˉ value on the rotational excitation of the NH fragment.     

Photodissociation of spatially aligned acetaldehyde cations

Photofragment translational energy and angular distributions are reported for the photodissociation of acetaldehyde cations in the wavelength range 354-363 nm obtained using the DC slice ion imaging technique. Vibrationally selected parent ions were produced by 2+1 resonance-enhanced multiphoton ionization (REMPI) via the 3s<--n Rydberg transition, with photodissociation resulting from absorption of a fourth additional photon. Three product channels were observed: HCO+, CH3CO+, and CH4+. The angular distributions reveal that all product channels have a predominantly parallel recoil anisotropy although the lower beta2 parameter of CH3CO+ indicates the concomitant presence of a perpendicular component. Furthermore, the distinct angular distribution of the CH3CO+ fragments shows a large value of the higher order Legendre polynomial term, providing evidence that acetaldehyde cations are spatially aligned during the ionization process.