环戊酮C_5H_8O的同步辐射真空紫外光电离解离研究

利用同步辐射光源,研究了环戊酮(C5H8O)在真空紫外105～140 nm波段的光电离和光解离过程.通过质谱测量各离子的光电离效率曲线,得到了该分子的垂直电离能及主要碎片离子的出现势.从理论上利用G3方法,计算了母体和中性及离子碎片的结构和能量,估算了各解离通道所需的解离能.结合实验测量值和理论计算值,指认出环戊酮分子可能的光电离解离通.     

1,2-环氧辛烷的同步辐射光电离解离研究

利用同步辐射产生的真空紫外光和反射式飞行时间质谱仪,在超声冷却条件下测量了1,2-环氧辛烷在光子能量9.8~16.6 eV能区的光电离解离过程,获得了不同能量光子作用下的电离解离产物。通过测量各离子的光电离效率曲线,得到了主要碎片离子的出现势。结合G3理论计算得到了母体离子、中性碎片及离子碎片的结构与能量,通过对比实验测量值与理论值给出了1,2-环氧辛烷的光电离解离通道.     

丙酮分子的共振增强多光子电离解离过程的实验研究

报道了在280—286.5nm区域内，通过共振增强多光子电离-飞行时间质谱和质量选择光电离激发谱对丙酮分子的光电离和光解离通道进行了研究，并对部分碎片离子的分质量激发谱进行了归属和标识.实验结果表明，在280—286.5nm紫外光波段内，丙酮分子以母体分子的电离通道为主，即首先电离生成母体离子然后母体离子再吸收光子解离生成碎片离子. 关键词： 丙酮 共振增强多光子电离 飞行时间质谱     

溴乙烷的同步辐射光电离解离

在超声射流条件下,利用真空紫外同步辐射光辐照和飞行时间质谱,研究溴乙烷光电离及解离电离的动力学。通过测量光电离及解离电离产生的碎片离子的光电离效率（ＰＩＥ）曲线型分布获得了溴乙烷的电离势和各碎片离子的出现势,并结合标准的已确认的热力学数据,计算了离子的标准生成焓,估算了有关分子的键能及母体离子的解离能,并对溴乙烷分子真空紫外光解离电离通道进行了分析。     

丙烯腈的真空紫外光电离研究

利用同步辐射真空紫外光和飞行时间质谱,研究了丙烯腈的真空紫外光电离解离过程。通过测量各离子的光电离效率曲线,获得了丙烯腈的电离势和各种碎片离子的出现势。分析了主要碎片离子的光电离解离通道,并结合有关热力学数据,算出它们的标准生成焓。并分析了它们的光电离解离通道及其随激发能量变化的竞争情况。     

α-蒎稀光电离和离解动力学的同步辐射研究（英文）

为研究α-蒎稀的光电离解离机制,采用同步辐射光电离质谱,在7.9~15.5 e V能量范围内研究了α-蒎稀的紫外光电离解离,对α-蒎稀的电离解离能及其碎片离子的出现势进行了理论分析.实验测得光电离效率曲线,从光电离效率曲线中获得α-蒎稀C_(10)H_(16)的电离能和碎片离子C_9H~+_(13),C_7H~+_(10),C_3H_6~+及CHH_3~+的出现势.用Gaussian 03理论方法计算了C_(10)H_(16)和主要的光解离碎片的总能量,用高级能量计算方法计算了C_(10)H_(16)的电离能和部分碎片离子的出现势及主要的解离通道的离解能.根据实验和理论计算结果,分析了产生碎片离子的主要的解离通道.分析表明实验测得的结果与理论计算提出的C_(10)H_(16)的光解离通道获得的解离能符合得较好.     

800 nm激光作用下碘乙烷的多光子电离解离研究

在800nm飞秒激光作用下对碘乙烷多光子电离解离过程进行了研究,获得了碘乙烷分子的多光子电离飞行时间（MPI-TOF）质谱.光强指数分析表明母体离子主要发生3+3共振增强多光子电离（REMPI）过程.根据部分碎片离子占总离子信号的百分比对激光强度的依赖关系,讨论了碘乙烷的多光子电离解离机制,得出了C₂H₅I分子的多光子电离（MPI）属于母体离子离解阶梯模式.文中分析了母体离子在该波长下主要两条解离通道,其中C-I键的断裂为主要通道.应用高斯03在B3LYP/3-21G基组上计算了两条通道能量的变化,理论进一步验证了实验结果的合理性.     

二甲基硫分子的共振增强多光子电离解离过程的实验研究

本文报道了在280~286.5 nm区域内,通过共振增强多光子电离-时间飞行质谱和质量选择光电离激发谱对二甲基硫分子的光电离和光解离通道进行了研究.实验结果表明,在280~286.5 nm区域内,二甲基硫分子以母体分子的电离通道为主,即首先电离生成母体离子然后母体离子再解离生成碎片离子.     

噻吩和吡啶的同步辐射光电离解离

利用同步辐射产生的真空紫外光，研究了噻吩和吡啶的光电离解离过程，测定了它们的电离电势及其碎片离子的出现势；利用有关势力学数据，估算了某些离子的标准生成焓；分析了它们的紫光电离解离通道。在实验中还观测到噻吩和吡啶多聚体离子的存在，并讨论了它们的可能结构。     

甲胺分子的同步辐射光电离解离质谱

在超声射流冷却条件下,利用同步辐射光源,结合飞行时间质谱对CH3NH2分子在60—140nm波长范围内的光电离解离进行了研究.主要动力学过程为母体离子的解离过程.CH2NH2+和CH3+由CH3NH2+在高能量时解离生成,而CH2NH2+的1,1脱H2过程则产生其他离子.CH3NH2分子的电离势(IP)为916±001eV,和分子轨道能量计算的理论值符合得非常好,并获得CH3NH2+和CH2NH2+的生成热分别为860±05kJmol和7541kJmol. 关键词： 同步辐射光电离 飞行时间质谱 电离势 生成热     

三氯乙烯的真空紫外同步辐射光电离和光解离

利用真空紫外(VUV)同步辐射光源和反射式飞行时间质谱仪，在超声冷却条件下对三氯乙烯(C₂HCl₃)进行了光电离研究，通过测量各离子的光电离效率(PIE)曲线，得到了C₂HCl₃的电离势P_I(C₂HCl₃)=9.51±0.05eV，以及C₂HCl₃光解离碎片离子的出现势(P_A)：P_{关键词： 同步辐射光电离 电离势 出现势 三氯乙烯}     

四氯乙烯的同步辐射光电离研究

利用VUV同步辐射光源和反射式飞行时间质谱仪，在超声冷却条件下对四氯乙烯(C₂Cl₄)进行了光电离研究，通过测量各离子的光电离效率(PIE)曲线，得到了C₂Cl₄的电离势IP(C₂Cl₄) =(9.36±0.05)eV及C₂Cl₄光解离碎片离子C₂Cl₃⁺，C_{关键词： 真空紫外光电离 离子出现势 电离势 四氯乙烯}     

Synchrotron radiation VUV double photoionization of some small molecules

The VUV double photoionizations of small molecules (NO,CO,CO2 ,CS2 ,OSC and NH3 ) were investigated with photoionization mass spectroscopy using synchrotron radiation. The double ionization energies of molecules were determined with photoionization efficiency spectroscopy. The total energies of these molecules and their parent dications (NO2+ ,CO2+ ,CO2+2 ,CS2+2 ,OSC2+ and NH2+3 ) were calculated using the Gaussian 03 program and Gaussian 2 calculations. Then,the adiabatic double ionization energies of the molecules were predicated by using high accuracy energy mode. The experimental double ionization energies of these small molecules were all in reasonable agreement with their respective calculated adiabatic double ionization energies. The mechanisms of double photoionization of these molecules were discussed based on a comparison of our experimental results with those predicted theoretically. The equilibrium geometries and harmonic vibrational frequencies of molecules and their parent dications were calculated by using the MP2 (full) method. The differences in configurations between these molecules and their parent dications were also discussed on the basis of theoretical calculations.     

Dissociative multiple photoionization of Br2, IBr,and I2 in the VUV and X-ray regions: a comparative study of the inner-shell processes involving Br(3d,3p,3s) and I(4d,4p,4s,3d,3p)

Dissociative multiple photoionization of the bromine, the iodine monobromide, and the iodine molecules in the Br(3d,3p,3s) and I(4d,4p,4s,3d,3p) inner-shell regions has been studied by using time-of-flight (TOF) mass spectrometry coupled to synchrotron radiation in the ranges of 90∼978 eV for Br₂, 60∼133 eV for IBr, and 86∼998 eV for I₂. Total photoion and photoion–photoion coincidence (PIPICO) yields have been recorded as functions of the photon energy. Here, giant shape resonances have been observed beyond the thresholds of the inner-shells owing to the Br(3d¹⁰)→Br(3d⁹ϵf), I(4d¹⁰)→I(4d⁹ϵf), and I(3d¹⁰)→I(3d⁹ϵf) transitions. The dissociation processes of the multiply charged parent ions have also been evaluated from variations of photoelectron–photoion coincidence (PEPICO) and PIPICO spectra with the photon energy. From each Br(3p_3/2) (189.9 eV) and I(4p_3/2) threshold (129.9 eV), quintuple ionization of the molecules begins to play important roles in the photoionization, subsequently yielding ion pairs of X³⁺–X²⁺ (X=Br, I). From the I(3d_5/2) threshold (627.3 eV), loss of six electrons from iodine molecule additionally begins to play a minor role in the multiple photoionization, giving rise to the formation of ion pairs of either I³⁺–I³⁺ or I⁴⁺–I²⁺. A direct comparison of the strengths and the ranges of the I(4d) and Br(3d) giant resonances was successfully made from dissociative photoionization of IBr. Over the entire energy range examined, 60<E<133 eV, biased charge spread relevant to the specific core-hole states of IBr is observed, presumably reflecting the fact that charge localizes mostly in the excited atoms, which can be accounted for mainly by a two step decay via a fast dissociation followed by autoionization upon the VUV absorption.     

甲苯光电离解离理论研究

The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods.The geometries and frequencies of the reactants,transition states and products have been performed at B3LYP/6-311++G (d,p) level,and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level.The ionization energies of toluene and the appearance energies for major fragment ions,C₇H₇⁺,C₆H₅⁺,C₅H₆⁺,C₅H₅⁺,are determined to be 8.90,11.15 or 11.03,12.72,13.69,16.28 eV,respectively,which are all in good agreement with published experimental data.With the help of available published experimental data and theoretical results,four dissociative photoionization channels have been proposed:C₇H₇⁺+H,C₆H₅⁺+CH₃,C₅H₆⁺+C₂H₂,C₅H₅⁺+C₂H₂+H.Transition structures and intermediates for those isomerization processes are determined in this work.Especially,the structures of C₅H₆⁺ and C₅H₅⁺ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.     

Synchrotron radiation VUV double photoionization of CHF2Cl

VUV double photoionization of CHF₂Cl in an energy region 32–40 eV was investigated with photoionization mass spectroscopy by using synchrotron radiation. The double ionization energy of CHF₂Cl and appearance energies for its main fragment dications (CHCl²⁺, CF₂²⁺ and CHFCl²⁺), were determined with photoionization efficiency spectroscopy for the first time. The single point energies of CHF₂Cl and its parent dication (CHF₂Cl²⁺) were calculated using Gaussian 03 program and density functional theory (DFT and B3LYP functional). The vertical double ionization energy of CHF₂Cl was predicted by using B3LYP method and empirical equation. According to our research results, the experimental double ionization energy of CHF₂Cl is in good agreement with the theoretically calculated vertical double ionization energy. The mechanism of double photoionization of CHF₂Cl was discussed based on the comparison of our experimental results with those predicted theoretically.     

Relative intensities in X-ray photoelectron spectra.: Part VIII

The photoionization cross-sections for the 3s and 3p shells of atomic Si, P, S, and Cl and the S²⁺ ion, and for the 2s and 2p shells of atomic F have been calculated using the random-phase approximation with exchange (RPAE) for the average-configuration term. Using the theoretical atomic cross-section values, the partial cross-sections for photoionization of the SF₆ molecule have been calculated for hv ? 54 eV and the photoelectron spectra have been interpreted. The calculation of relative intensities in the photoelectron spectra of H₂S is presented. The influence of the effective charge of an atom on the photoionization cross-section value for a molecular level is shown.     

Electron spectroscopy using excited atoms and photons IV. Penning ionization of ethylene

Using helium metastable atoms (2¹S, 2³S), the Penning ionization of C₂H₄ has been studied using a high resolution electrostatic electron analyzer. The Franck—Condon envelope for the ground state of C₂H₄⁺ (X²B_3u) is found to be the same for He* (2³S) Penning ionization and 584 Å photoionization. The ΔE shift values and the relative electronic transition probabilities are reported for four ionic states. Unusually large differences have been found for the relative electronic transition probabilities for Penning ionization and photoionization.     

Photoionization cross sections and oscillator strengths of neutral cesium

The absolute photoionization cross sections from the 6p ²P_1/2 excited state of cesium at threshold and above the threshold region have been measured using the saturation absorption technique. The photoionization cross section at the ionization threshold is determined as 22.6±3.6 Mb, whereas in the region above threshold its value ranges from 22 to 20 Mb for photoelectron energies up to 0.1 eV. A comparison of the photoionization cross sections with earlier reported theoretical and experimental data have been presented and are in good agreement within the uncertainty. In addition, the oscillator strengths of the 6p ²P_1/2→n d ²D_3/2 (21≤n≤60) Rydberg transitions of cesium have been calibrated using the threshold value of the photoionization cross section. A complete picture of the oscillator strengths from the present work and previously reported data from n=5–60 is presented.     

Dissociative photoionization of l-menthone: An experimental and theoretical study

The dissociative photoionization mechanism of l-menthone has been investigated with photoionization mass spectrometry using synchrotron radiation. The adiabatic ionization energy (IE) of l-menthone and the appearance energies (AE) of its major fragment ions C₉H₁₅O⁺, C₉H₁₇⁺, C₈H₁₆⁺, C₇H₁₁O⁺, C₆H₁₀O⁺, C₆H₉O⁺, C₅H₈O⁺, C₅H₁₀⁺, C₄H₆O⁺, C₅H₉⁺, C₄H₈⁺, C₄H₇⁺, C₃H₇⁺, C₃H₆⁺, C₂H₂O⁺, and CH₃⁺ are determined with their photoionization efficiency (PIE) spectra in the photon energy region of ∼8−15.5 eV. Breakdown diagrams identifying the major products are presented. Dissociative photoionization channels for formation of these fragment ions are proposed based on comparison of determined experimental appearance energies and energies predicted with the DFT calculations. According to our results, the experimental dissociation energies are in fair agreement with the theoretical values of the possible photodissociation channels of C₁₀H₁₈O.