自由基的同步辐射研究进展

通过同步辐射光电离质谱可以测得自由基的电离能，出现势，并可求得其离解能，质子亲和能以及相关物质的生成热等热化学数据。自由基的同步辐射荧光激发谱对研究光解通道以及超激发态分子的衰变过程有重要价值。     

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…     

1,4-二氧六环的光电离解离

采用同步辐射光源、飞行时间质谱和分子束方法研究了1．4-二氧六环的光电离解离过程．由光电离效率曲线得出离子产物的出现势，计算了产物的生成焓．若重分析了m／e=28,29.41等离子碎片的解离通道以及离子碎片的可能结构，提出1、4-二氧六环在光电离解离过程中发生了重排反应     

丙烯齐聚反应产物的气相色谱/质谱分析

采用GC MS分析技术对丙烯催化齐聚液相产物进行了分离、定性和定量分析。毛细管色谱柱为PONA柱 (5 0m× 0 .2 5mm× 0 .2 5 μm) ,FID检测器 ,He作载气 ,初温 3 5℃ ,以 3℃ min升至 2 80℃ ,恒温 60min。质谱离子源为EI源 ,能量 70eV ,离子源温度 2 0 0℃。结果表明丙烯齐聚液相产物中各组分可得到较好地分离 ,主要组分为短支链度的异构烯烃 ,另外还含有少量烷烃和环烷烃 ;由质谱图确定了 1 0 7个组分的化学结构     

PS自由基的形成及动力学研究

本文研究了亚稳态原子He(23S)和Ne(3P0.2)与PSCl3分子的反应,获得了PS(B2Ⅱ→X2Ⅱ)和PS(C2→X2Ⅱ)二个谱带的发射光谱.根据碎片的光谱,研究了PS(B2Ⅱ)和PS(C2Ⅱ)的形成速率和振动布居.     

Fenton反应考察抗坏血酸清除羟基自由基能力及动力学

自由基的清除对维持正常的生理活动和抗衰老具有重要意义。 抗坏血酸(V_C)是常用的天然抗氧化剂之一, 为了有效合理利用V_C的抗氧化性, 实验利用水杨酸捕捉Fenton反应产生的羟基自由基(·OH), 加入V_C考察与水杨酸竞争清除·OH的能力, 选择出最佳清除条件;并根据双底物反应特征, 拟合出Alberty方程, 得到了清除·OH的规律。 结果表明, 当V_C用量为4.54 mmol/L、温度为47 ℃条件下、反应90 min时, V_C对·OH的清除率达到最大, 为46.23%;拟合出的反应动力学参数最大反应速率为0.11 mmol/(L·min), 水杨酸和V_C 的特征常数分别为30.2和1.2×10^-3 mmol/L。 比较实验结果和拟合方程得到的数据, 二者非常接近, 相对误差在1.66%~5.40% 之间, 从而为合理利用抗坏血酸清除羟基自由基提供理论依据。     

脉冲激光引发自由基聚合的动力学研究

处理了无链转移时脉冲激光引发自由基聚合中的动力学问题:推导出聚合产物数均和重均分子量的严格数学表达式,给出了链自由基、死聚物及总的聚合产物的归一化的分子量分布函数,计算结果表明:随着单体转化率的上升,各种分子参数,例如数均和重均分子量,以及多分散指数的数值周期性地振荡,且振幅逐渐下降,分子量分布曲线则包含一些特征峰,且随着每次脉冲激光产生的初级自由基浓度的降低,分布曲线峰的数目增加,另外,与歧化终止相比,偶合终止使产物的分子量分布略为变窄.     

243～263nm CH3COCH3 的多光子电离研究

在243～263 nm紫外光波段通过质量选择光电离激发谱研究了丙酮（CH3COCH3）的光化学反应通道。分析母体离子CH3COCH3+和碎片离子CH3CO+ 、 CH3+的光电离激发谱和质谱峰宽可以知道: 此光波段丙酮分子的光化学反应主要包括了丙酮分子经由(S1,T1)中间态产生母体离子的（1+1）双光子电离通道,母体离子进一步解离产生碎片离子CH3+的“光电离-光解离”通道和丙酮分子经由(S1,T1)中间态解离成中性自由基碎片CH3CO后再进一步被双光子电离的“光解离-光电离”通道。由母体离子光电离激发谱双光子阈值波长（255.67 nm）给出的丙酮电离势（IP）为（9.696±0.004）eV。     

南瓜子油的气相色谱-质谱分析

黑龙江产白皮南瓜子油脂含量约为27％，从提取的南瓜子油中检测出大量的共轭亚油酸、磷脂、角鲨烯、环烷烃、共轭不饱和醛酮、植物甾醇等化学成分，其中植物甾酵的含量约占南瓜子油的1％，能确定结构的甾醇有6种。     

Identification of Intermediates in Pyridine Pyrolysis with Molecular-beam Mass Spectrometry and Tunable Synchrotron VUV Photoionization

The pyrolysis of pyridine （5.26% pyridine in argon） was performed with tunable synchrotron vacuum ultraviolet photoionization and molecular-beam mass spectrometry technique at the temperature range of 1255-1765 K at 267 Pa. About 20 products and intermediates, containing major species H2, HCN, C2H2, C5H3N, C4H2, and C3H3N, were identified by near-threshold measurements of photoionization mass spectra and their mole fractions vs. temperatures were estimated. The major reaction pathways are analyzed based on the experimental observations.     

Synchrotron Photoionization Study of the Diisopropyl Ether Oxidation

Scientific evidence has shown oxygenates help to reduce dangerous pollutants arising from burning fossil fuel in the automotive sector. For this reason, their use as additives has spread widely. The aim of this work consists in providing a comprehensive identification of the main primary oxidation products of diisopropyl ether (DIPE), one of the most promising among etheric oxygenates. The Cl-initiated oxidation of DIPE is examinated by using a vacuum ultraviolet (VUV) synchrotron radiation at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). Products are identified on the basis of their mass-to-charge ratio, shape of photoionization spectra, adiabatic ionization energies, and chemical kinetic profiles, at three different temperatures (298, 550, and 650 K). Acetone, propanal, propene, and isopropyl acetate have been identified as major reaction products. Acetone is the main primary product. Theoretical calculations using the composite CBS-QB3 method provided useful tools to validate the postulated reaction mechanisms leading to experimentally observed species. The formation of other species is also discussed.     

有机质谱学法研究气相S_N2离子－分子反应进展

总结了近年来应用质谱方法研究气相SN2离子－分子反应的进展，主要包括气 相SN2离子－分子反应的机理，动力学和热力学的各种因素。与凝固相中反应对比 ，阐明了影响反应机理、方向与程度的决定性因素，及溶剂化效应对凝聚相中反应 的影响方式。还介绍了一些气相中特有的SN2离子－分子反应和研究气相反应特殊 的质谱学研究方法与技术。     

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。     

Photoionization and Dissociative Photoionization Study of Cholesterol by I R Laser Desorption/Tunable Synchrotron VUV Photoionization Mass Spectrometry

Elementary cholesterol was analyzed with IR laser desorption/tunable synchrotron vacuum ultraviolet photoionization mass spectrometry. An exclusive molecular ion of cholesterol is observed by near threshold single-photon ionization with high efficiency. Fragments are yielded with the increase of photon energy. The structures of various fragments are determined with commercial electron ionization time-of-flight mass spectrometry. Dominant fragmentation pathways are discussed in detail with the aid of ab initio calculations.     

Real-Time Distinguishing of the Xylene Isomers Using Photoionization and Dissociation Mass Spectra Obtained by Femtosecond Laser Mass Spectrometry (FLMS)

Abstract

Distinguishing chemicals and improvement on analytical methods has a direct impact on modern chemical analysis. In this work, the dissociative ionization of xylene isomers was investigated using a femtosecond laser mass spectrometry (FLMS) method with a custom-built linear time-of-flight (TOF) instrument. Laser beams at 800?nm and 400?nm were used and intensity-dependent analysis of the obtained mass spectra was performed using principal component analysis (PCA) to distinguish the xylene isomers, which give identical mass spectra in appearance that cannot be distinguished using normal mass spectrometry methods. The results show that there is a statistically highly significant difference between the xylene isomers for two principal components (1 ? α?>?99.99%) and minimal information loss (<5%) took place during the PCA procedure. Also, the use of the k-medoid clustering method showed that the isomers may be distinguished in real-time for a wide range of ionization laser pulse powers with approximately 99% accuracy. The results suggest that real-time isomer analysis by the FLMS method is suitable for mass spectral identification applications. The FLMS method has been shown to be an important alternative to other mass spectrometric methods that use different ionization mechanisms.     

同步辐射光电离质谱法研究卷烟主流烟气气相成分

利用同步辐射光电离质谱法对卷烟主流烟气气相成分进行了研究。首先,利用针筒捕集主流烟气气相成分,在未进行样品处理和分离的情况下,实时、在线获得烟气的光电离质谱图;再扫描光电离效率(PIE)谱,获得气相成分的电离能(IE),并对其进行归属;最后,以商用吸烟机对卷烟进行抽吸,获得单口烟气中甲醇、乙炔等化学成分相对含量随抽吸口数增加的变化情况,并探讨了可能原因。     

Base-Assisted Conversion of Protonated D-Fructose to 5-HMF: Searching for Gas-Phase Green Models

A gas-phase investigation of the D -fructose dehydration reaction in the presence of base has been performed by the joint application of mass spectrometric techniques and theoretical calculations. Protonated addition products of D -fructose and base were generated in the gas phase by electrospray ionization using several bases of different proton affinity. The intermediates, products and decomposition channels were investigated by ion trap mass spectrometry. Electronic structure calculations allowed the identification of the ionic intermediates and products of a selected system containing NH₃, helping to rationalize the observed reaction pathways. The obtained results show that the final product, the protonated 5-hydroxymethyl-2-furaldheyde [5-HMF]H⁺, is better formed using selected bases and only if these remain clustered until the end of the dehydration process.     

Organic Reactions in Microdroplets: Reaction Acceleration Revealed by Mass Spectrometry

The striking finding that reaction acceleration occurs in confined‐volume solutions sets up an apparent conundrum: Microdroplets formed by spray ionization can be used to monitor the course of bulk‐phase reactions and also to accelerate reactions between the reagents in such a reaction. This Minireview introduces droplet and thin‐film acceleration phenomena and summarizes recent methods applied to study accelerated reactions in confined‐volume, high‐surface‐area solutions. Conditions that dictate either simple monitoring or acceleration are reconciled in the occurrence of discontinuous and complete desolvation as the endpoint of droplet evolution. The contrasting features of microdroplet and bulk‐solution reactions are described together with possible mechanisms that drive reaction acceleration in microdroplets. Current applications of droplet microreactors are noted as is reaction acceleration in confined volumes and possible future scale‐up.