Photodissociation of RbI in an Intense Laser Field: Detection of the Product Metal Atom Rb Using RIMS

It is reported on the recent research using resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) to detect the photodissociation product of Rubidium iodide molecules in a molecular beam in an intense laser field. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed.     

Photodissociation of RbI in an Intense Laser Field: Detection of the Product Metal Atom Rb Using RIMS

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｔｈｅｍｅｔｈｏｄｏｆｒｅｓｏｎａｎｃｅｉｏｎｉｚａｔｏｎｓｐｅｃｔｒｏｓｃｏｐｙ (ＲＩＳ)ｗａｓｉｎｔｒｏｄｕｃｅｄｉｎｔｈｅｅａｒｌｙ 1970ｓｆｏｒｔｈｅｕｌｔｒａ ｓｅｎｓｉｔｉｖｅｄｅｔｅｃｔｉｏｎｏｆａｔｏｍｓ .Ａｓｔｈｅｎａｍｅｉｍｐｌｉｅｓ ,ｉｎｔｈｅｔｅｃｈｎｉｑｕｅｉｏｎｓｈａｖｅｔｏｂｅｄｅｔｅｃｔｅｄ ;ｓｉｎｃｅｔｈｅｃｏｌｌｅｃｔｉｏｎｏｆｉｏｎｓｉｓｕｓｕａｌｌｙｃｏｎｓｉｄｅｒａｂｌｙｍｏｒｅｓｅｎｓｉｔｉｖｅａｎｄｅｆｆｉｃｉｅｎｔｔｈａ…     

对硝基苯乙醚的真空紫外光电离与光离解研究

以同步辐射为光源,用光电离质谱和符合技术对对硝基苯乙醚分子进行了真空紫外光电离与光离解研究。测得了这一分子的电离势及C6H5NO+3、C6H5O+2、C6H5O+等六个主要碎片离子的出现势,根据实验所得的质谱图、能量关系,结合该分子的具体结构,初步分析了该分子同步辐射光离解电离的可能通道,并得到了分子离子的键离解能D0(O2NC6H4C2H+5)。     

In-source resonance ionization spectroscopy of high lying energy levels in atomic uranium

In-source resonance ionization spectroscopy of uranium has been carried out as preparation for the analysis of low contaminations of nuclear material in environmental samples via laser mass spectrometry. Using three-step resonance ionization spectroscopy, 86 levels of odd parity in the energy range from 37,200–38,650 cm^???1 were studied, 51 of these levels were previously unknown. Suitable excitation schemes for analytic applications are discussed.     

Cobalt coated substrate for matrix-free analysis of small molecules by laser desorption/ionization mass spectrometry

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.     

The analysis of alkyl-capped alcohol ethoxylates and alcohol ethoxycarboxylates from alcohol ethoxylates by atmospheric pressure chemical ionization mass spectrometry

Alcohol ethoxylates (AEs) are nonionic surfactants. They are industrially important compounds that have historically been difficult to analyze, with the best results to date achieved through derivatization (e.g., silylation) followed by analysis by gas chromatography/mass spectrometry (GC/MS). Recently, mass spectrometric techniques such as field desorption (FD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) have been employed to analyze surfynol(R) 4xx. In an effort to produce low-cost alkyl-capped AEs and anionic detergents from AEs, a fast and reliable measure of the product yields and conversions from AEs is required in research. We found that the product yields and conversions from reactions of AEs, obtained by the employment of atmospheric pressure chemical ionization (APCI), were in good agreement with those obtained from proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Therefore, APCI can be used as a validated tool for studying AE reactions. Mixtures that contain either silylated or unsilylated ethoxylates and/or carboxylates yield the same APCI mass spectra. Copyright -Copyright 1999 John Wiley & Sons, Ltd.     

利用静电场中光电离效率谱精确确定1,3-二乙氧基苯分子的电离能

电离能是原子和分子的重要的特性参数,在光物理和光化学过程中起着重要作用,精确电离能对相关研究具有重要意义.电离能是调试零动能光谱信号的重要参考数据,在判断异构物数量和分子构型方面也起着关键作用.1,3-二乙氧基苯是一种重要的苯的衍生物,实验证实在超声分子束中包含两种旋转异构物Ⅰ(downup)和Ⅲ(down-down).它们的精确电离能还未见文献报道.本文采用直线式飞行时间质谱仪测量了静电场中1,3-二乙氧基苯光电离效率曲线,通过不同电场强度下测量的电离能(Stark效应)对场强的平方根线性拟合给出了两种异构物Ⅰ和Ⅲ精确的电离能分别为(62419±2)cm^–1和(63378±2)cm^–1.相对于通常的脉冲电场加速机制和零动能光谱测量的电离能,精确度大约分别由(±10)cm^–1和(±5)cm^–1提高到(±2)cm^–1.分析和讨论了不同方法测量的物理机制和优缺点.     

The production of sub-micron sodium nitrate particles by laser ablation

Laser ablation is a useful source of particles for chemical analysis by inductively coupled mass spectroscopy in many applications. Optimum particle transport and ionization requires particles with sizes in the range 0.1-2 7m. Significant questions remain as to the mechanisms behind particle production by laser ablation. In this work, we collect and observe particles produced from single-crystal sodium nitrate during irradiation at 1.06 7m as a function of fluence and explore the possibility that laser-induced fracture may produce suitable particles. At fluences between 3 and 4 J/cm², single laser pulses incident on cleaved samples produce large numbers of fracture particles as a result of the fracture of undercut cleavage steps. Polished samples, lacking cleavage steps, yield few, if any, particles. As the fluence is raised to 5 J/cm², a small breakdown plume is observed and large melted droplets (~10 7m in diameter) are produced from both cleaved and polished targets, presumably by spallation of a thick melted layer. Particle generation by fracture has the potential to produce particles whose composition closely matches the local sample composition.     

The ionization potentials of clustered sodium atoms

Small clusters of sodium atoms have been produced by the isentropic flow of high pressure vapour through a small orifice. These clusters have been ionized by ultra-violet light and detected using a mass spectrometer. Clusters of up to eight sodium atoms have been observed and their ionization potentials have been measured. The ionization potentials of Na₃ and Na_s are 3.9 v and 4.0 v respectively, showing that even the smallest clusters tend to the value expected for a continuous drop of metal of the same size.     

Products of the interaction of veratrole and paraform in a subcritical water medium

The interaction of veratrole and paraform in a subcritical water medium was studied and the macrocyclic compounds (cyclotriveratrylene and cyclotetraveratrylene) were obtained in a ratio of 94: 6. The formation of the aforementioned compounds is confirmed by complex analytical methods, including mass spectrometry with electrospray ionization (ESI MS) and NMR spectroscopy. The data of ESI MS showed that the mixed adducts of the above macrocycles of trimer-cation-tetramer type are formed.     

Exploration of gold nanoparticle beams for matter wave interferometry

We investigate molecular beam methods for gold nanoparticles. They are based on electrospray, matrix assisted laser desorption and thermal laser desorption in combination with mass spectroscopy and multi-photon ionization. These techniques are analyzed with respect to their potential for coherent matter wave experiments.     

Photoelectron Spectroscopy, Photoionization Mass Spectroscopy, and Theoretical Study on CCl3SSCN

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．     

激光光谱技术在环境监测中的应用专题系列（Ⅲ）：激光质谱法对机动车尾气中污染物的实时监测

激光质谱法通过共振增强多光子电离把紫外光谱和飞行时间质谱结合起来,是具有高选择性、快速和高灵敏度的痕量化学污染物质分析方法。文章介绍了其原理和在机动车尾气监测上的应用。     

Resonance ionization mass spectroscopy for nuclear research and trace analysis

Resonance ionization mass spectroscopy (RIMS) has been applied, firstly, to a study of the nuclear properties of short-lived Au isotopes at the on-line isotope separator ISOLDE at CERN and, secondly, to a trace-analysis experiment of Pu.     

Ionization Scheme Development at the ISOLDE RILIS

The resonance ionization laser ion source (RILIS) of the ISOLDE on-line isotope separation facility is based on the method of laser step-wise resonance ionization of atoms in a hot metal cavity. The atomic selectivity of the RILIS complements the mass selection process of the ISOLDE separator magnets to provide beams of a chosen isotope with greatly reduced isobaric contamination. Using a system of dye lasers pumped by copper vapour lasers, ion beams of 24 elements have been generated at ISOLDE with ionization efficiencies in the range of 0.5–15%. As part of the ongoing RILIS development off-line resonance ionization spectroscopy studies carried out in 2003 and 2004 have determined the optimal three-step ionization schemes for scandium, antimony, dysprosium and yttrium.     

A NEW EXPERIMENTAL METHOD IN THE STUDY OF IONIC RYDBERG STATES BY RESONANCE IONIZATION MASS SPECTROSCOPY

We report a new method for detecting highly excited ions. With a strong constant electric field ionization following the extracting of ions by a pulsed electric field in a time-of-flight mass spectrometer, the direct multi-photon ionization background can be eliminated in laser multi-step resonance ionization mass spectroscopy of ionic Rydberg states. A high detection efficiency call be obtained for law members of ionic Rydberg states by use of this method. We have applied the method in the study of the spectroscopy of ionic Rydberg states ia ytterbium.     

Stepwise ionization of the 2,4-dioxybenzaldehyde and 3,4-dimethoxypropiophenone vapors

The processes of stepwise ionization of the 2,4-dioxybenzaldehyde and 3,4-dimethoxypropiophenone vapors by radiation in the range of wavelengths down to 266 nm were studied using total-current spectroscopy, mass spectrometry, and photoelectron spectroscopy. The process of two-step ionization and the resulting generation of molecular ions are dominant if the laser-radiation intensity amounts to ≈10⁶ W/cm². These molecular ions have appreciable (up to 1.8 eV) energy of vibrational excitation. As the laser-radiation intensity increases, progressively more pronounced fragmentation occurs owing to dissociation of molecular (and, possibly, fragmentation) ions as a result of absorption of at least a single additional photon. The processes leading to fragmentation of ions are suggested. It is found that the dissociation-ionization mechanism is important for the dimethoxypropiophenone. Dissociation with a breakage of the α bond in the carbonyl group with subsequent two-photon ionization of the fragments occurs when the S ₂(¹ A′) state of the ππ* type is excited.     

Ultra-fast laser pulses provide an ion source for highly selective mass spectroscopy

The mass spectra of two isomers of butane, 1-butene and cis-2-butene, interacting with linearly polarized Ti:sapphire laser pulses, were compared. It was demonstrated that the difference between the two spectra are much more pronounced than the corresponding spectra prepared by 100 eV electron ionization ion source. In addition, the difference could be varied by changing the peak laser intensity. The observation suggests potential application of dissociative multiphoton ionization by ultrafast laser pulses as a source for high performance mass spectroscopy.     

光谱分析方法在同位素检测中的研究和应用进展

同位素在核工业为主的各种工业生产中受到广泛的关注,并推动着地质学、材料科学、化学等相关学科的发展。近年来,基于光谱分析原理的同位素分析方法的开发逐渐受到关注。虽然多接收杯电感耦合等离子体质谱（MC-ICP-MS）、热电离质谱（TIMS）和气体同位素质谱（IRMS）等质谱技术是同位素分析的标准方法,但是这些质谱方法通常需要复杂的样品前处理流程以及频繁的仪器维护。光谱分析方法在这些方面有着自身独特优势,甚至可以满足现场实时快速的同位素分析,并在核工业同位素分析和传统稳定同位素分析领域已经取得了日益广泛的应用。随着光谱仪器关键部件和数据处理方法的进一步发展,极大地改善了光谱法同位素分析的性能（灵敏度、分辨率和精密度）,使光谱分析方法被逐渐开发并应用于环境和地质同位素分析领域。综述了光谱分析方法在同位素分析（定量或定性）领域的主要进展,从光谱分析原理的角度归类为发射光谱（原子发射、分子发射、拉曼光谱）和吸收光谱（原子吸收、分子吸收）两大类。着重讨论了光谱法进行同位素分析的基本原理、发展历程以及重要进展,简述了与质谱法相比的优缺点。针对仍然有待突破的技术难点,展望了光谱法应用于同位素分析的发展前景。该综述可为光谱分析方法在同位素检测中的发展方向提供重要参考。     

Cold rubidium molecules formed in a magneto-optical trap

We report the first observation of translationally cold ( approximately 90 &mgr;K) Rb2 molecules. They are produced in a magneto-optical trap in their triplet ground state. The detection is performed by selective mass spectroscopy after two-photon ionization into Rb+2, resonantly enhanced through the intermediate a (3)Sigma(+)(u)-->2 (3)Pi(g) molecular band. The two rubidium isotopes present very different types of behavior that are interpreted in terms of their respective collisional properties.