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1.
汽油/氧气预混火焰中烯丙基自由基的真空紫外光电离研究 总被引:1,自引:0,他引:1
分子束取样结合同步辐射光电离质谱技术研究了低压汽油/氧气/氩气预混火焰中的烯丙基自由基,测得了它的光电离效率曲线,通过光电离效率曲线得到烯丙基的电离阈值为(8.13±0.02)eV。另外,用从头算分子轨道理论得到了烯丙基及其阳离子的构型和能量,给出了烯丙基自由基的绝热电离能为8.18 eV。计算的电离能与实验得到的电离能符合得很好,这一结果有助于今后鉴别和分析其它火焰中的烯丙基自由基,且对研究火焰燃烧机理有十分重要的价值。 相似文献
2.
G. Delacrétaz J. D. Ganière R. Monot L. Wöste 《Applied physics. B, Lasers and optics》1982,29(1):55-61
A supersonic molecular beam, pulsed laser and time-of-flight mass spectrometer are arranged together in order to study photo- and auto-ionization, two-photon-ionization and fragmentation processes of alkali clusters as a function of the laser wavelength. In spite of an unfavourable duty cycle, however, the apparatus reaches a considerably higher sensitivity than cw experiments. Alkali clustersM
n
(n21) have been observed and investigated. The well resolved TOF mass spectra are commonly accompanied by significant and broad signals of metastable ions, a phenomenon which cannot be observed by quadrupole mass spectrometry. ParticlesM
n
(n4) have been investigated by twophoton ionization using two different laser wavelengths. Several new electronic transitions for Na3 are found; commonly, however, the excitation and ionization channels are accompanied by strong fragmentation processes. The fragment patterns are very sensitively dependent upon the laser wavelength even when working near the ionization threshold. The results are a strong indication, that the peak intensities of cluster mass spectra cannot easily be related to the intensity distribution of the neutral cluster beam. 相似文献
3.
偶氮苯的同步辐射光电离研究 总被引:1,自引:0,他引:1
用同步辐射光电离质谱与符合技术的相结合测定了偶氮苯光电离效率谱,获得了该分子的电离势,导出了分子和分子离子中某些键的解离能以自由基C6H5N2的电离势。测得了不同光子能量激发下的质谱图,并对不同能量时偶氮苯的解离电离方式进行了分析。 相似文献
4.
利用同步辐射真空紫外光,研究了HFC-152a(CH3CHF2)的光电离和光解离过程,通过测量各离子的光电离效率曲线,得到了该分子的电离能(11.94±0.04eV)和所有碎片离子的出现势,运用GAUSSIAN-03程序计算了母体和碎片及相应离子的结构、电子态和能量. 结合理论计算的结果,分析了母体离子可能的光电离解离通道及相关通道的解离能.
关键词:
同步辐射
光电离
出现势
HFC-152a 相似文献
5.
用合肥国家同步辐射实验室光化学站的实验装置研究了苯分子的光电离质谱,从所得光电离效率谱精确地定出了苯分子的电离势及苯离子的出现热,并首次报道了三个苯离子的离解能。 相似文献
6.
We examined the application of mass spectrometric methods using resonant ionization by a tunable laser and proposed its use
for analyzing hydrogen isotopes. We conducted resonance ionization mass spectrometry (RIMS) to detect gas-phase hydrogen isotope
atoms. The ionization efficiency was increased by more than 1000 times that obtained with conventional methods using nonresonant
ionization. Resonant laser ablation mass spectrometry (RLAMS) was applied for deuterium detection in solid samples. A graphite
substrate implanted with deuterium was used for ordinary laser ablation mass spectrometry (LAMS) and RLAMS. The deuterium
signal was observed very clearly by RLAMS, in contrast to LAMS. Mass spectrometry combined with resonance ionization was very
useful for hydrogen isotope detection, because components with equal mass numbers were resolved and the method demonstrated
higher ionization efficiency.
Received: 4 November 1998 / Revised version: 12 January 1999 / Published online: 7 April 1999 相似文献
7.
Abstract Mass spectrometric techniques are playing a predominant role for the determination of transuranium elements in bulk samples as well as in microparticles. Their applications to liquid and solid samples for the determination of the isotopic composition as well as for the concentration measurements are discussed. The new developments for the characterization of microparticles stemming from different release scenarios of radioactivity are considered. Inductively coupled plasma mass spectrometry and its hyphenation with other techniques for resolving isobaric interferences are presented. The application of glow discharge and laser ablation directly to solid samples is highlighted. Finally, the exploitation of secondary ion mass spectrometry, accelerator mass spectrometry, resonance ionization mass spectrometry, and thermal ionization mass spectrometry for the determination of the isotopic composition of uranium and plutonium in microparticles is illustrated. 相似文献
8.
9.
Mohammadreza Shariatgorji Nahid Amini Leopold L. Ilag 《Journal of nanoparticle research》2009,11(6):1509-1512
Conventional matrix-assisted laser desorption/ionization mass spectrometry is limited to analyses of higher molecular weight
compounds due to high background noise generated by the matrix in the lower mass region. Surface-assisted laser desorption/ionization
(SALDI) mass spectrometry is an alternative solution to this problem. Nanoparticles, structured silicon surfaces and carbon
allotropes are commonly used as SALDI surfaces. Here, for the first time, we demonstrate the application of silicon nitride
nanoparticles as a suitable medium for laser desorption/ionization of small drug molecules. 相似文献
10.
Abstract Mass spectrometry (MS) has progressed to become a powerful analytical tool for both quantitative and qualitative applications. The first mass spectrometer was constructed in 1912 and since then it has developed from only analyzing small inorganic molecules to biological macromolecules, practically with no mass limitations. Proteomics research, in particular, increasingly depends on MS technologies. The ability of mass spectrometry analyzing proteins and other biological extracts is due to the advances gained through the development of soft ionization techniques such as electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) that can transform biomolecules into ions. ESI can efficiently be interfaced with separation techniques enhancing its role in the life and health sciences. MALDI, however, has the advantage of producing singly charges ions of peptides and proteins, minimizing spectral complexity. Regardless of the ionization source, the sensitivity of a mass spectrometer is related to the mass analyzer where ion separation occurs. Both quadrupole and time of flight (ToF) mass analyzers are commonly used and they can be configured together as QToF tandem mass spectrometric instruments. Tandem mass spectrometry (MS/MS), as the name indicates, is the result of performing two or more sequential separations of ions usually coupling two or more mass analyzers. Coupling a quadrupole and time of flight resulted in the production of high-resolution mass spectrometers (i.e., Q-ToF). This article will historically introduce mass spectrometry and summarizes the advantages and disadvantages of ESI and MALDI along with quadrupole and ToF mass analyzers, including the technical marriage between the two analyzers. This article is educational in nature and intended for graduate students and senior biochemistry students as well as chemists and biochemists who are not familiar with mass spectrometry and would like to learn the basics; it is not intended for mass spectrometry experts. 相似文献
11.
This paper reports an investigation on typical organics contained in ambient aerosols with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The VUV-ATOFMS utilizes a vacuum ultraviolet krypton lamp as an ionization source. The single- and multi-constituent particles generated with typical atmospheric organics (n-eicosane, n-triacontane, 1-pentadecanol, 1-eicosanol, hexanoic acid, decanoic acid, heptadecanoic acid, oleic acid, succinic acid, pyrene, vanillin, benzoic acid, terephthalic acid, and D-galactose) are analyzed with VUV-ATOFMS. The time-of-flight mass spectra of all organic particles are obtained except hexanoic acid. The mass spectra reveal that the detection efficiencies for a certain compound contained in multi-constituent and single-constituent particles are different. These discrepancies may result from the different evaporation dynamics of aerosols in both atomization and vaporization processes. The pyrene has the strongest signal intensity in single- or multi-constituent aerosols, indicating that the VUV-ATOFMS performs well in detecting polycyclic aromatic hydrocarbons. These experimental results present a view on the VUV-photoionization mass spectra of the 14 typical organics contained in ambient aerosols. 相似文献
12.
实验研究了钛原子在293~321 nm波段的共振增强多光子电离. 采用激光烧蚀和超声射流相结合的实验技术来制备自由原子,由飞行时间质谱仪实现对钛原子光电离产物的检测. 从离子信号强度对和激光强度的依赖关系导出了钛原子价电子激发态的光电离截面. 实验测量的一些激发态光电离截面在0.2~6.0 Mb. 通过对46Ti、47Ti、48Ti的光电离截面测量研究,没有发现明显的同位素依赖性. 相似文献
13.
X. M. Zhang J. T. Zhang R. X. Li Q. H. Gong Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(3):457-462
Photoionization of hydrogen atoms in few-cycle laser pulses is studied
numerically. The total ionization probability, the instantaneous ionization
probability, and the partial ionization probabilities in a pair of opposite
directions are obtained. The partial ionization probabilities are not always
equal to each other which is termed as inversion asymmetry. The variation of
asymmetry degree with the CE phase, the pulse duration and the pulse intensity
is studied. It is found that the pulse intensity affects the asymmetry degree
in many aspects. Firstly, the asymmetry is more distinct at higher intensities
than that at lower intensities when the pulse duration exceeds 4 cycles;
secondly, the maximal asymmetry in lower intensities varies with the CE phase
visibly while at higher intensities not; thirdly, the partial ionization
probabilities equal to each other for some special CE phases. For lower pulse
intensities, the corresponding value of CE phase is always 0.5π and
1.5π, while for higher pulse intensities, the corresponding value varies
with the pulse intensity. Similar phenomena were observed in a recent
experiment using few-cycle radio-frequency (RF) pulses. 相似文献
14.
15.
Abstract Atmospheric pressure ionization (API) mass spectrometry is a novel form of mass spectrometry in which the ionization process is carried out in a reaction chamber external to the mass analyzer region. The mass analyzer serves as a device to detect positive or negative ions present in the reaction chamber, which is maintained at atmospheric pressure. 相似文献
16.
通过一种简单的方式产生了CCl3SSCN,并利用光电子能谱(PES)和光电离质谱(PIMS)对该化合物进行了表征.通过理论计算得知, 该分子围绕S-S键的二面角为91.4 o . 这种扭曲结构是S-S键上的孤对电子的相互作用导致的.电离后基态的自由基离子CCl3SSCN¢+呈平面的反式构象(δCSSC=180o),且具有Cs对称性.CCl3SSCN分子的最高占据轨道(HOMO)为硫原子的3p孤对电子轨道:3pπf51a(nS(CCl3S))g-1. 实验得到的该分子的第一垂直电离能为10.40 eV. 相似文献
17.
Intravenous hypnotic propofol and its metabolite are detected in real time during total intravenous anesthesia by an electron
ionization mass spectrometer. The mass spectrometer is connected directly to the breathing circuit of an apparatus for inhalational
anesthesia. Ratios between the propofol concentrations in expired air and blood serum are measured. It is concluded that real-time
noninvasive monitoring of the propofol concentration in blood using electron ionization mass spectrometry is feasible. 相似文献
18.
Small molecule analysis is one of the most challenging issues in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. We have developed a cobalt coated substrate as a target for matrix-free analysis of small molecules in laser desorption/ionization mass spectrometry. Cobalt coating of 60-70 nm thickness has been characterized by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and laser induced breakdown spectroscopy. This target facilitates hundreds of samples to be spotted and analyzed without mixing any matrices, in a very short time. This can save a lot of time and money and can be a very practical approach for the analysis of small molecules by laser desorption/ionization mass spectrometry. 相似文献
19.
本文采用同步辐射真空紫外光电离质谱法和理论计算方法,研究了吗啉单体的光电离、解离及随后的裂解反应.实验测得吗啉单体的垂直电离能为8.37 eV(±0.05),与理论计算值8.41 eV相当吻合.实验观察到荷质比为86、57和29的吗啉碎片离子.实验和理论结果表明:荷质比为86的碎片是通过失去氢原子而产生的,而荷质比为57的碎片是通过开环消除CH_2O而形成的;荷质比为29的碎片是通过消除C_2H_4从碎片离子(C_3H_7N)~+(m/z=57)进一步解离而产生的.这一发现为研究脂肪族化合物的光损伤提供了有价值的见解,可能被转化为活细胞和其他生物系统. 相似文献
20.
Technical Physics - Possible effects of ionization phenomena on the analytical signal in inductively coupled plasma mass spectrometry with a high-temperature ion source are considered. The... 相似文献