Tunable light sources based on high harmonics generation for time-resolved VUV spectroscopy

The project of set-up for time resolved femtosecond VUV spectroscopy, which is based on a high harmonic generation source and a VUV monochromator is presented. We discuss the generation conditions of quasi-continuous VUV spectrum via HHG in Ar using the intense chirped IR fundamental pulse and the relatively weak second harmonic of IR fundamental. The desired narrow VUV spectral range is selected by time compensated double monochromator with concave spherical diffraction gratings. PACS 42.65.Ky; 42.79.Dj; 78.47.+p; 39.30.+w     

Reliability evaluation for failed fuel identification using resonance ionization mass spectrometry

In the fast reactors, rapid and accurate identification of a fuel failure event is essential for ensuring safety operation. Isotopic analysis of krypton (Kr) and xenon (Xe) using resonance ionization mass spectrometry (RIMS) is an effective identification tool, in which Kr and Xe atoms are resonantly ionized by a pulsed laser at 216.7 nm and 249.6 nm, respectively, and then three isotopic ratios: ⁷⁸Kr/⁸⁰Kr, ⁸²Kr/⁸⁰Kr and ¹²⁶Xe/¹²⁹Xe are measured to detect the location of the failed fuel assembly. In this paper, we report on the required analytical precision of RIMS estimated from simulation studies as well as the analytical performance of our spectrometer to evaluate the availability of RIMS to the failed fuel identification technique in the fast reactors.     

Frequency mixing in a gas-filled waveguide for VUV light generation

Advantages of nonlinear frequency-mixing in gas-filled waveguides to generate vuv radiation are analyzed. Under phase-matching conditions the waveguides are shown to provide a much higher conversion efficiency (up to 10²÷10⁴ times) as compared to the tight focusing into the bulk gas medium. Estimations of the improvements for cw and pulse vuv generation are presented.     

Hyperfine structure induced isotopic effects in krypton resonance ionization mass spectrometry

A time-of-flight mass spectrometer combined with a pulsed laser system has been used for determination of krypton isotope ratios of air samples containing 10⁶-10⁷ krypton atoms. A three-color, doubly resonant ionization scheme employing a 116.48 nm transition from the ground into the first 4s²4p⁵(²P°_1/2)5s J = 1 excitation level has been applied. The magnitude of a hyperfine splitting of this level has been estimated for ⁸¹Kr, ⁸³Kr and ⁸⁵Kr isotopes. Hyperfine structure induced isotopic effects have been investigated under different saturation conditions and found to be negligible when the first and the second transitions are strongly saturated.     

Development of high resolution resonance ionization mass spectrometry for trace analysis of 93mNb

⁹³Nb(n, n′)^93mNb reaction allows retrospective estimation of integrated fast neutron dose in nuclear reactor. We proposed isomer-selective trace analysis of ^93mNb by Resonance Ionization Mass Spectrometry (RIMS) combined with a gas-jet atomic source and an injection locked Ti:Sapphire laser system operated at several kHz. Resonant ionization spectroscopy of Nb in gas-jet using Ti:Sapphire laser was demonstrated.     

Combustion chemistry probed by synchrotron VUV photoionization mass spectrometry

Combustion is directly related to energy conversion and the environment. Gas-phase chemical reactions such as thermal decomposition, oxidation and recombination play a critical role in combustion processes. Here we review six applications of synchrotron vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS) in fundamental studies of combustion chemistry. These applications range from the use of flow reactors to probe elementary reaction kinetics, studies of pyrolysis in plug-flow reactors and oxidation in jet-stirred reactors, studies of spatial evolution of species concentrations in premixed and non-premixed flames, product distributions in pyrolysis of biomass, and analysis of polycyclic aromatic hydrocarbon (PAH) formation. These experiments provide valuable data for the development and validation of detailed chemical kinetic models. Furthermore, some additional potential applications are proposed.     

KrF离子准分子真空紫外辐射及动力学过程

利用激光等离子体软Ｘ射线激励，观察到一种新型离子准分子－ＫｒＦ离子准分子的真空紫外连续谱，其辐射中心波长位于１４８ｎｍ附近，并在实验和理论上对其动力学过程进行分析。     

VUV synchrotron radiation: a new activation technique for tandem mass spectrometry

A novel experimental technique for tandem mass spectrometry and ion spectroscopy of electrosprayed ions using vacuum‐ultraviolet (VUV) synchrotron radiation is presented. Photon activation of trapped precursor ions has been performed by coupling a commercial linear quadrupole ion trap (Thermo scientific LTQ XL), equipped with the electrosprayed ions source, to the DESIRS beamline at the SOLEIL synchrotron radiation facility. The obtained results include, for the first time on biopolymers, photodetachment spectroscopy using monochromated synchrotron radiation of multi‐charged anions and the single photon ionization of large charge‐selected polycations. The high efficiency and signal‐to‐noise ratio achieved by the present set‐up open up possibilities of using synchrotron light as a new controllable activation method in tandem mass spectrometry of biopolymers and VUV‐photon spectroscopy of large biological ions.     

Field ionization mass spectrometry of organic compounds

A review is given on field ionization mass spectrometry of organic compounds. Four different subjects are treated and illustrated by means of significant examples: Experimental techniques, surface reactions induced by high electric fields, the kinetics of fast unimolecular decompositions of ions, and qualitative and quantitative analyses of organic compounds by field desorption methods.     

Multiple peak formation in laser ionization mass spectrometry

Molecules in the source region of a time of flight mass spectrometer are ionized by ultraviolet laser radiation. Under certain conditions mass spectra consisting of a remarkably periodic set of ion peaks are generated. It is demonstrated that these result from spatially periodic ionization within the mass spectrometer which is a consequence of the development of standing electromagnetic waves.     

Collison nebulizer as a new soft ionization source for mass spectrometry

We have proposed that a Collison-type nebulizer be used as an ionization source for mass spectrometry with ionization under atmospheric pressure. This source does not require the use of electric voltage, radioactive sources, heaters, or liquid pumps. It has been shown that the number of ions produced by the ⁶³Ni radioactive source is three to four times larger than the number of ions produced by acoustic ionization sources. We have considered the possibility of using a Collison-type nebulizer in combination with a vortex focusing system as an ion source for extractive ionization of compounds under atmospheric pressure. The ionization of volatile substances in crossflows of a charged aerosol and an analyte (for model compounds of the amine class, viz., diethylaniline, triamylamine, and cocaine) has been investigated. It has been shown that the limit of detecting cocaine vapor by this method is on the level of 4.6 × 10^–14 g/cm³.     

Ion cyclotron resonance mass spectrometry of acetylene

Ion-molecule reactions of acetylene have been studied by ion cyclotron resonance mass spectrometry in the pressure range 1–10 × 10⁻⁶ torr. The results are in good agreement with those obtained using tandem and high-pressure source instruments. The major products from the molecular ion are C₄H₂⁺ and C₄H₃⁺ and at 12.5 eV, I(C₄H₂⁺)/I(C₄H₃⁺) was found to be 0.455. This ratio was found to vary slightly with electron energy. Double-resonance experiments showed that the ions C⁺, CH⁺, C₂⁺, C₂H⁺, and C₂H₂⁺ all react with acetylene in reactions of the type

and that these reactions are major sources of C₃ and C₄ ions. The variation of double-resonance line-shapes with the amplitude of the irradiating oscillator is discussed.     

Development of laser ablation assisted resonant ionization mass spectrometry for isotope analysis

Stable isotope analysis using Laser Ablation Assisted Resonant Ionization Mass Spectrometry (LA-RIMS) is discussed. For the case of the ⁸⁷Sr/⁸⁶Sr isotope ratio measurements with a single color two-photon excitation scheme, the mass discrimination effects, which occur in LA-RIMS, are analyzed and a precision of 0.6% was extracted. For preparation of LA-RIMS on Hf isotopes, a novel two-color resonant excitation scheme with subsequent non-resonant ionization has been established using a high repetition-rate Ti:Sapphire laser system.     

Influence of light statistics on the many photon resonance ionization

We study the influence of laser temporal coherence on the width and shape of induced resonances in the many photon ionization.     

Silver nanoparticles as matrix for laser desorption/ionization mass spectrometry of peptides

Silver nanoparticle synthesized from chemical reduction has been successfully utilized as a matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) of peptides. Acting as a substrate to adsorb analytes, as well as a transmission medium for UV laser, silver nanoparticle was found to assist in the desorption/ionization of peptides with little or no induced fragmentation. The size of the nanoparticle was typically in the range of 160 ± 20 nm. One of the key advantages of silver nanoparticle for peptides analysis is its simple step for on-probe sample preparation. In addition, it also minimizes the interferences of sodium dodecyl sulfate (SDS) surfactant background signal, resulting in cleaner mass spectra and more sensitive signal, when compared to α–cyano-4-hydroxycinnamic acid (CCA) matrix.