对硝基苯乙酮的同步辐射光电离与离解研究

利用同步辐射先电高质谱法对对硝基苯乙酮（p－nitroacetophenone，pNAP）进行了光电离与光离解的实验研究，测定了pNAP的电离势以及该分子离解电离生成主要碎片离子的出现势等物理化学数据，并对该分子的离解电离通道进行了初步分析．另外，用从头计算法和密度泛函理论研究了该分子电离前后的稳定构型及能量，得到了不同理论水平和不同基组下的电离势．

HX_(2)^(+)(X=Cl,Br)离子的密度函数理论(DFT)研究

选取密度泛函方法 ,采取 6 - 311++G(2df ,2 pd)基组对单态HCl+ 2 和HBr+ 2 离子进行了理论计算。考虑到HF+ 2 离子中D∞h结构可独立存在的事实 ,文中首次对HCl+ 2 和HBr+ 2 离子的包含D∞h在内的四种可能几何构型进行了优化计算 ;求得了Cl2 与Br2 的质子亲和能及Cl—ClH+ 与Br—BrH+ 的键分离能 ,丰富和完善了对HCl+ 2 的理论计算 ,并对HBr+ 2 离子存在的可能性进行了计算研究 ,结果预言HBr+ 2 单态中Cs 结构为其平衡结构。最后给出了HCl+ 2 和HBr+ 2 的热化学数据、力常数等数值 ,并给出了基态HBr+ 2 离子的离解通道 ,从而给出其完全离解时的离解能 。

丙烯酸甲酯的真空紫外光电离质谱研究(英文)

利用同步辐射光和反射飞行时间质谱,研究了丙烯酸甲酯9.0～15.5eV能量范围的真空紫外光电离和光解离.实验测量丙烯酸甲酯的光电离质谱和解离碎片离子m/e =86(C4H6O2+),85(C4H5O2+),59(C2H3O2+),58(C3H6O+) ,55(C3H3O+),42(C3H6+),31(CH3O+),27(C2H3+),和15(CH3+)的光电离效率曲线.并利用量子化学从头算(G3),计算碎片离子的能级,推测它们的解离通道.计算的电离能和出现势与实验结果符合很好.结果表明,丙烯酸甲酯的光电离解离通道以单键断裂反应为主.

Dissociative Photoionization of 1,4-Dioxane with Tunable VUV Synchrotron Radiation

The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C4H7O2^＋, C3H6O^＋, C3H5O^＋, C2H5O^＋, C2H4O^＋, C2H3O^＋, C3H5^＋, CH3O^＋, C2H6^＋, C2H5^＋/CHO^＋, C2H4^＋ and CH3^＋ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31＋G（d,p） level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.

Dissociative Photoionization of 1,2-Epoxyoctane Studied with Synchrotron Radiation

Dissociative photoionization of 1,2-epoxyoctane was investigated by synchrotron radiation vacuum ultraviolet photons in the energy region of 9.8-16.6 eV under ultrasonic molec-ular beam. Dissociative fragment ions were measured with reffection time-of-ight mass spectrometer at di erent photon energies. Appearance potentials of the dominative ion fragments were determined through photoionization efficiency curves. The structures and energies of the parent, ionized and neutral radicals were obtained with G3 calculations. Through comparing the experimental results with the theoretical calculations, we proposed the dissociative channels for the photoionization of 1,2-epoxyoctane.

Photofragmentation of Isoleucine by Vacuum Ultraviolet Photoionization

Vacuum ultraviolet photon-induced ionization and dissociation of isoleucine are investi- gated with synchrotron radiation photoionization mass spectroscopy and theoretical cal- culations. The main fragment ions at m/z=86, 75, 74, 69, 57, 46, 45, 44, 41, 30, 28, and 18 from isoleucine are observed in the mass spectrum at the photon energy of 13 eV. From the photoionization efficiency curves, appearance energies for the principal fragment ions CsH12N＋ （rn/z=86）, C2H5NO2＋ （m/z=75）, C5H9＋ （rn/z=-69）, C4H9＋ （m/z=57）, and CH4N＋ （m/z=30） are determined to be 8.844-0.07, 9.254-0.06, 10.20-4-0.12, 9.254-0.10, and 11.05＋0.07 eV, respectively, and possible formation pathways are established in detail by the calculations at the B3LYP/6-31＋＋G（d, p） levels. These proposed channels include simple bond cleavage reactions as well as reactions involving intermediates and transition structures. The experimental and computational appearance energies or barriers are in good agreement.

Competition Between Two Excitation-dissociation Channels for Molecular Ions

When the molecular ions XYZ＋ （XY2＋） are excited simultaneously from an electronic state E0 into two higher electronic states Ea and EZ with supervened dissociation or predisso- ciation, competition between the α and β excitation-dissociation channels occurs. A the- oretical model is provided to deal with the competition of the two excitation-dissociation channels with more than two kinds of ionic products for XYZ＋ （XY2＋）. Supposing that the photo-excitation rates of two states Eα and Eβ are much less than their dissociation or pre-dissociation rates, a theoretical equation can be deduced to fit the measured data, which reflects the dependence of the product branching ratios on the intensity ratios of two excitation lasers. From the fitted parameters the excitation cross section ratios are obtained. In experiment, we studied the competition between two excitation-dissociation channels of CO^2＋. By measuring the dependence of the product branching ratio on the intensity ratio of two dissociation lasers and fitting the experiment data with the theoretical equation, excitation cross section ratios were deduced.

Theoretical Study of Isoprene Dissociative Photoionization

Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7＋, C5H5＋, C4H5＋, C3H6＋, C3H5＋, C3H4＋, C3H3＋ and C2H3＋, which were observed experimentally from the isoprene dissociative photoionization. The energy calculations were performed with the CBS-QB3 model. All the geometries and energies of the fragments, intermediates and transition states involved in the dissociations channels were determined. Finally, the mechanisms of the dissociation pathways were discussed on the comparison of theoretical and experimental results.

Photodissociation of acryloyl chloride in the gas phase

The 193 nm photodissociation dynamics of CH2CHCOC1 in the gas phase has been examined with the technique of time-resolved Fourier transform infrared emission （TR-FTIR） spectroscopy. Vibrationally excited photofragments of CO （v ≤ 5）, HC1 （v ≤ 6）, and C2H2 were observed and two photodissociation channels, the C-C1 fission channel and the HC1 elimina- tion channel have been identified. The vibrational and rotational state distributions of the photofragments CO and HC1 have been acquired by analyzing their fully rotationally resolved v→ v- 1 rovibrational progressions in the emission spectra, from which it has been firmly established that the mechanism involves production of HC1 via the four-center molecular elimination of CH2CHCOC1 after its internal conversion from the S1 state to the So state. In addition to the dominant C--C1 bond fission along the excited S1 state, the S1→S0 internal conversion has also been found to play an important role in the gas phase photolysis of CH2CHCOC1 as manifested by the considerable yield of HC1.