丁酮分子的共振增强多光子电离解离研究

利用可调谐染料激光研究了丁酮分子的共振增强多光子电离解离过程,发现在428～448nm激光波段丁酮分子发生的是经4p和4dRydberg态的(3+1)多光子过程。此外,我们还用“梯开关”模型对丁酮母体离子的解离机理和各碎片来源作了详细的分析,分析认为在丁酮母体离子的解离过程中存在H原子重排与电荷的重新分布现象。     

丁酮分子3d态的共振增强多光子电离

酮类分子含有羰基,其价电子跃迁主要涉及ＣＯ成键π轨道,Ｏ原子的非键２ｐｙ轨道和ＣＯ反键π轨道,它们的能量顺序为π＜２ｐｙ＜π,里德堡态由最高占有轨道２ｐｙ(ｎ０)的一个孤对电子向各里德堡轨道跃迁产生［１］．ＶＵＶ吸收谱［１,２］和电子能谱［１,３］都显...     

烯丙基6~8eV之间电子振动光谱的共振增强多光子电离研究

在分子束中用高温热解3-碘代丙烯的方法产生烯丙基,并结合飞行时间质谱和2+1共振增强多光子电离技术,从实验上观测到了烯丙基从基态到6~8eV之间的6个电子态3d_xz, 3d_xy,ns(n=4,6,7,8)的电子振动光谱.在ns的Rydberg态电子振动光谱中可以观测到v₇(∠CCC弯曲振动)约为430cm^-1的振动级数.由Rydberg公式拟合得到烯丙基的绝热电离能为(65641±20)cm^-1((8.138±0.002)eV).     

甲胺分子多光子电离质谱研究

胜多光子电离飞行时间质谱法，利用可调谐脉冲激光器，测得了甲胺分子在不同激光波长和激光功率下的多光子电离和解离产物。母体离子ＣＨ３ＮＨ＾＋２的离解速常数随激光发波长的增大而减小。     

OCS分子的共振多光子电离光谱

OCS分子的真空紫外吸收光谱早有研究,但有关OCS分子的多光子电离光谱尚未见报导。我们利用可调脉冲激光器,研究了OCS分子的共振多光子电离光谱。首次观察到OCS分子在277—285nm波长范围内的多光子电离光谱。OCS由硫氰酸铵和硫酸反应制取,经多次低温蒸馏纯化。产物通过FT-IR红外光谱和     

二甲胺同步辐射光电离解离机理的质谱研究

利用同步辐射光源，结合飞行时间质谱，在超声射流冷却条件下研究了(CH_3) _2NH(DMA)的光电离解离机理。实验观察到四种主要离子(CH_3)_2NH·~+， CH_3NH~+CH_2，CH_2NH_2~+和CHNH~+，质荷比分别为m/z = 45，44，30和28。四种 离子的出现势（AE）分别为8.26，9.52，11.93和11.27 eV，其中分子电离热IP = （8.26 ± 0.01） eV，计算得到分子离子的生成热Δ_fH~o = 778.55 kJ/mol。 分析表明离子CH_3NH~+CH_2来自母体离子的α去H过程。其他碎片离子由后续逐级 解离去H反应以及脱CH_3通道生成。     

共振增强多光子电离耦合飞行时间质谱研究甲烷脱氢芳构化反应

 采用共振增强多光子电离耦合飞行时间质谱技术，初步探测了甲烷无氧芳构化反应。实验结果表明，该技术具有灵敏度高，质量分辨率高，响应时间快等优点，改变波长能实现对目标产物的实时，高灵敏度检测，并且可以获得所有产物的信息。     

二乙胺分子的多光子电离：“梯转换”过程

二乙肤的红外光谱[1]和泛频吸收谱[2]有一定研究，其电子轰击电离[3，4]、场致电离[5]和电子轰击所产生离子的红外多光子及碰撞解离[6]表明，母体离子的碎裂以α键的断裂，从而失去甲基并形成亚胺离子为主．二乙胺分子中N原子与其他原子的构型成锥形，而在母体离子中则成平面结     

碘代烷烃在532 nm激光作用下多光子电离解离机理

利用５３２ｎｍ的激光对碘代烷烃（碘甲烷、碘乙烷、碘代正丙异丙烷）分子作了多光了电离解离（ＭＰＩＤ）质谱（ＭＳ）研究,在５３２ｎｍ激光作用下,ＣＨ３Ｉ分子吸收５３２ｎｍ激光双光子的能量,进入Ａ带的ＩＡ２态,继续吸收光子上泵浦至电离态形成母体离子ＣＨ３Ｉ,然后再形成碎片离子;而其它几个碘代烷烃吸收双光子的能量进入Ａ带后均形成中性碎片,中性碎片再吸收光子经一系列电离解离形成碎片离子,此外,本文还通过对同     

二乙胺分子的多光子电离："梯转换"过程

The multiphoton ionization (MPI) of diethylamine is first reported in this paper. A time-of-flight mass spectrometer was used in the experiment under collision-free condition. MPI mass spectra were measured in the region of 464 ～486 nm using a dye laser and at double frequency of a Nd:YAG laser. Molecular ion was created through resonance enhanced multiphoton ionization (REMPI) via Rydberg states. Fragment, ion distribution was formed through “ladder switching” process. The experimental demonstration of the process is reported for the first time by the discussion of dependence of ion relative, abundance on laser wavelength and energy. The competition between further up-pumping and fragmentation of Parent ion also exists, and higher laser intensity favors the former.     

Ionization and Fragmentation of Butanone Clusters Irradiated by Photons at 355 and 118 nm

Time-of-flight(TOF) mass spectra of molecular butanone clusters were measured under the irradiation of photons at 355 and 118 nm. Butanone molecular parent ion and several series of butanone cluster fragments such as (CH3COC2H5)nH+, (CH3COC2H5)nC2H5+, (CH3COC2H5)nCH3CO+ and (CH3COC2H5)nC2H5CO+ were observed. Odd-even variation pattern in the intensity of (CH3COC2H5)nCH3CO+ is obvious from n=4 to 8. A connection is es-tablished between the fragment clusters (CH3COC2H5)nCH3CO+ and the neutral clusters (CH3COC...     

Studies on Fragmentation of Peptide by Nano-electrospray Ionization Fourier Transform Ion Cyclotron Resonance Multi-stage Tandem Mass Spectrometry

The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry(Nano-ESI-FT-ICR-MSn) and several peptides were chosen as examples. With the aid of the collision induced dissociation(CID), FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation(SORI-CID) condition was proposed.     

Study of Electron Ionization and Fragmentation of Non-hydrated and Hydrated Tetrahydrofuran Clusters

Mass spectroscopic investigations on tetrahydrofuran (THF, C₄H₈O), a common model molecule of the DNA-backbone, have been carried out. We irradiated isolated THF and (hydrated) THF clusters with low energy electrons (electron energy ~70 eV) in order to study electron ionization and ionic fragmentation. For elucidation of fragmentation pathways, deuterated TDF (C₄D₈O) was investigated as well. One major observation is that the cluster environment shows overall a protective behavior on THF. However, also new fragmentation channels open in the cluster. In this context, we were able to solve a discrepancy in the literature about the fragment ion peak at mass 55 u in the electron ionization mass spectrum of THF. We ascribe this ion yield to the fragmentation of ionized THF clusters.

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Fragmentation of Some Substituted Phthalimides on Electron Impact Ionization

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｅｌｉｍｉｎａｔｉｏｎｓｏｆＣＯａｎｄＣＯ２ｆｒｏｍｔｈｅｍｏｌｅｃｕｌａｒｉｏｎｓｏｆｐｈｔｈａｌｉｍｉｄｅａｎｄｉｔｓＮ－ｍｅｔｈｙｌ,Ｎ－ｐｈｅｎｙｌｄｅｒｉｖａｔｉｖｅｓｉｎｍａｓｓｓｐｅｃｔｒｏｍｅｔｒｙｗｅｒ...     

乙胺和二甲胺分子(n N,3s)里德堡态共振的多光子电离

The multiphoton ionization spectra of ethylamine and dimethylamine are presented in the 400-470nm region, with resonance excitation to 3s Rydberg state. The MPI fragmentation patterns of two C2H7N isomers are readily distinguished. For ethylamine, the most prevalent fragmentation is β-Cleavage, while for dimethylamine that is H atom ejection.     

乙胺和二甲胺分子(n_N,3s)里德堡态共振的多光子电离

MPI质谱研究作为化学分析和研究光物理过程的工具受到广泛的重视[1－4]．REMPI的特征过程是，首先分子吸收。个光子共振激发到中间态，然后处于中间激发态的分子再吸收n个光子激发到电离连续区[5]．REMPI的谱特征可以给出中间态分布的详细信息[6]，利用REMPI过程可研究单光子跃     

山奈甲黄素-3,7-二-O-多取代黄酮苷的串联质谱研究

利用电喷雾串联质谱研究了几种从狗枣猕猴桃叶中提取得到的糖基取代山奈甲黄素的碎裂规律. 结果表明, 由于碎裂规律不同, 3,7-二-O-取代山奈甲黄素能够和3-O或者7-O单取代山奈甲黄素区分: 单取代山奈甲黄素主要失去取代糖基生成黄酮苷元的碎片, 而3,7-二-O-取代黄酮主要失去某一处取代糖基生成相应的碎片离子([ ]^－和[ ]^－), 而难观察到所有取代糖基都失去的黄酮苷元碎片离子. 并且由于[ ]^－和[ ]^－离子的进一步碎裂方式不同, 很容易将其区分开, 从而确定不同糖基的取代位置.     

Fragmentation Study of Limonoids from Turraae pubescens by Electrospray Ionization Quadrupole Time-of-flight Mass Spectrometry

Nine representative limonoids isolated from Turraae pubescens were investigated by electrospray ionization quadrupole time-of-flight tandem mass spectrometry in positive ion mode. Although the structures of these compounds are similar, the corresponding fragmentation patterns and mass spectrometry and tandem mass spectrometry (MS/MS) spectra are clearly different. For Turrapubin A–C, product ions can be detected in both low and high mass ranges. A McLafferty-type rearrangement is the only way for the cleavage of C9–C10. For 11-epi-toonacilin, Turrapubin E, Turraflorin A, 11-epi-23-hydroxytoonacilide, Turrapubin H and 11-epi-21-hydroxytoonacilide, the cleavage of C9–C10 goes through two different ways, including McLafferty-type rearrangement and homolytic cleavage. The relative abundances of product ions from McLafferty-type rearrangement for 11-epi-toonacilin, 11-epi-23-hydroxytoonacilide, and Turrapubin H are high, while those for Turrapubin E, Turraflorin A, and 11-epi-21-hydroxytoonacilide are low. A pair of epimers was distinguished unambiguously by MS/MS spectra. It was found that the substituent group at C-1, hydroxy group, O atom linked to C-14 and C-15, and the oxygenated furan ring were the important factors leading to the differences of their MS/MS spectra.     

H2三光子共振增强电离光谱中的反常压力效应

在H2和的三光子共振增强多光子电离光谱中观察到反常压力现象，其中有些是首次报导的．线移、线展宽、线分裂和光谱强度的负压效应都可以用三次谐波再吸收的机理解释．用考虑了相位区配条件导出的近似表达式计算的不同压力下线移、线分裂、光谱强度与实验结果一致．用新设计的串联二对电极的气体池得到的光谱直接证明了三次谐波再吸收的机理，圆偏振光实验无信号也支持上述机理．