Coupling of a Rydberg electron capture ion source with a quadrupole mass filter

International audienceThe coupling of a Rydberg electron capture ion source with a Nermag R10-10H quadrupole mass filter is described. Details are given of the addition to this instrument of a creation cell for atoms excited in Rydberg states. Within the Nermag ion source, such atoms allow attachment of electrons of well-defined thermal energy. SF 6 was used for optimization of the main experimental parameters (gas pressures and voltages applied to the electrodes). The procedure by which Rydberg electron attachment was confirmed is described. A polychlorobiphenyl compound was used to illustrate the performance of this ionization technique. Ion formation was observed in the absence of fragmentation. The real-time analysis of a sample from a mass spectrum presents numerous problems when a small quantity of complex molecules in an atmospheric matrix are to be analyzed. In particular, the number of ion fragments produced must be minimized and the presence of the molecules of interest must be ascertained with high specificity while the molecules of the matrix are disregarded. Current ion sources tend to limit fragmentation, for example by proton transfer in positive ion chemical ionization (PICI), 1,2 by thermal electron attachment in electron capture chemical ionization (ECCI), 3 or by means of an electron monochromator (EM). 4 Our Rydberg electron capture (REC) ion source comes within the perspective of a new low-fragmentation negative ion producing source. The ion source has been validated previously on several pollutants 5 using a quadrupole ion trap operated in a non-conventional mode. 6 It was decided to integrate such an ion source with a commercial apparatus. In this way, it was possible to obviate the problems of developing a new mass analysis apparatus 7 and to concentrate on the study of the ion source. In this paper, we present the results obtained after integrating an REC source in a quadrupole mass filter instrument, the Nermag R10-10H. Numerous molecules that are of interest in the environmental field 8,9 can attach an electron by resonant capture provided they have a sufficiently positive electron affinity. In general, many such molecules can attach electrons whose energy can be positive (free electrons) or negative (bound electrons) in a thermal energy range having an absolute value <1 eV. In this work, weakly bound electrons of xenon atoms excited in Rydberg states (designated as Xe**) created by electron bombardment were used. 10 The xenon atoms are excited to different energy levels and the corresponding Rydberg electrons have an energy dispersion of several tens of milli-electron volts. This technique is more straightforward and less costly than that which uses an electron monochromator, for example, for a lower energy dispersion of the electrons. Another great advantage of using Rydberg atoms is the possibility of maintaining at a constant value the energy of the electron even while it is going through zones subjected to weak electric fields; this experimental condition is impossible to achieve with free electrons. The REC process by a molecule MX is expressed by: MX Xe ÃÃ 3 MX ÀÃ Xe 1 The negative molecular ion produced by the reaction is metastable since it is created in an excited state. The lifetime values obtained by Rydberg electron attachment are greater than that which might be expected for attachment of a free electron. The ion is in a less excited state as a result of the negative energy of the Rydberg electron and of the presence of the 'third body' Xe (ion core of Xe**) involved in reaction (1). This Xe ion can stabilize the anion further when the energy level n of the electron is lower than 15. 11,12 Moreover, in the case of polyatomic molecules, the internal energy of the anion is redistributed over a large number of vibrational degrees of freedom. The lifetime is thus enhanced all the more. The electron attachment cross-section a is a function of the electron affinity and gives an indication of the ease with which the anions can be created. Generally, the cross-sections are not well known in the case of low-energy free electrons and Rydberg electrons. Various experimental and theoretical works concerning the Rydberg electron attachment rates on SF 6 molecules, and summarized by Dun-*Correspondence to

Performance enhancement of a Fourier transform ion trap mass spectrometer using indirect ion-motion frequency measurement

International audienceWe present a field mass spectrometer to analyse atmospheric pollutants and discuss the enhancement of its metrological performance. First of all, we describe the operating mode and the signal processing. Then, we deal with high voltage signals applied to the electrodes. We explain the characteristics of these signals which are quite different from those used in conventional ion trap mass spectrometers. We present the metrological parameters (mass range, sensitivity and mass resolution) of the analyser and the problems connected to the enhancement of its performance. The Fourier transform treatment leads to a very high sensitivity; the spectral signal-to-noise ratio is better than 4 for a mean number of ions of one. Resolution is limited by non-linearity of the confinement field. At present, the width at half maximum of the spectral peak is 0.052 u which leads to a mass resolution of 2500 for mass 132. To improve mass resolution, a more precise ion trap has been devised. To analyse heavier molecules, a new linear amplifier stage is being developed to supply a confinement AC voltage of a maximum amplitude of 1 kV

Ion exchange effect on asymmetric dioxins adsorption onto FAU-type X-zeolites

International audienceThe effect of trivalent cation exchange on fully dehydrated (activated) FAU-type X-zeolites with respect to the adsorption of the sterically biggest, asymmetric dioxin-molecules (1,2,3,4 TeCDD) in iso-octane solvent was investigated. FAU 13X Na zeolites were selected due to their pore openings, close to the diameter of the 2,3-DCDD (0.74 nm) as well as their high adsorption affinity for this dioxin molecule. This zeolite also adsorbed 1,4 DCDD, but with significantly lower affinity.With the aim to eventually liberate the channel's access for the sterically biggest dioxin molecule 1,2,3,4 TeCDD, Na+ cations were replaced by trivalent cation species Y3+, Ce3+ and La3+. Symmetric dioxins were not tested in this study due to their high toxicity.Analyses performed indicate that cation exchange reaches 80% on the zeolite, while the zeolite structure is preserved during the process. La3+-FAU-type X-zeolites showed the same extreme affinity towards 1,2,3,4 TeCDD as Na+ - FAU-type X-zeolites did for 2,3-DCDD. At the same time it could be shown that both dioxins could be separated by adsorption, while 1,2,3,4 TeCDD only interacts with the external surface of Na+-FAU-type X-zeolite, not entering the zeolite pores. (C) 2015 Elsevier Inc. All rights reserved

Rydberg electron-capture mass spectrometry of 1,2,3,4 tetrachlorodibenzo-p-dioxin

International audienceA negative-ion creation technique by Rydberg electron capture (REC) is used to ionise 1,2,3,4 tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD). Negative ions are mass-analysed by a commercial quadrupole mass spectrometer and also by a home-made mass spectrometer using a quadrupole ion trap. From spectra of 1,2,3,4-TCDD a comparison between the REC ionisation technique and two other soft ionisation techniques, electron capture chemical ionisation (ECCI) and the electron monochromator (EM), are discussed

Création d'atomes d'argon excités dans des états de Rydberg en vue de l'étude de l'autodétachement électronique d'ions moléculaires SF6 -6 dans un piège quadrupolaire radiofréquence

In this work, we describe experimental conditions to obtain argon atoms excited in Rydberg states by an electron gun. Precisions are given about some of their properties it is necessary to know with a view to the study of electronic autodetachment of SF6- molecular ions in a radiofrequency quadrupole trap. These ions are created by nearly-zero energy interaction of SF6 molecules with excited atoms in Rydberg states. In our experimental conditions, the excitation of argon atoms by electronic bombardment in such states has led us to bring to light a deflection angle of the excited atoms, an evaluation of the energy of the electrons which lead to electronic attachment, the number of created excited atoms, and an estimation of their related mean lifetime.Nous décrivons dans ce travail les conditions expérimentales d'obtention d'atomes d'argon excités dans des états de Rydberg par bombardement électronique. Nous précisons certaines de leurs propriétés qu'il est nécessaire de connaître dans la perspective de l'étude de l'auto-détachement électronique d'ions moléculaires SF6-dans un piège quadrupolaire radiofréquence. Ces ions sont créés par interaction, à énergie quasi-nulle, de molécules SF6 avec des atomes excités dans des états de Rydberg. Dans nos conditions expérimentales, l'excitation d'atomes d'argon dans de tels états par bombardement électronique nous a conduits, en particulier, à la mise en évidence d'un angle de déflection des atomes excités, à l'évaluation de l'énergie de l'électron donnant lieu à l'attachement électronique, au nombre d'atomes excités créés, ainsi qu'à une estimation de leur durée de vie moyenne correspondante

Measurement of Fission Products and Chemical Species released by Experimental Samples irradiated in the Jules Horowitz Reactor

International audienceExperiments on nuclear fuels and materials in MTRs are a mandatory step for supporting their characterization and qualification before introduction at industrial scale in power reactors. They are the most often carried out in irradiation loops and capsules embarking a lot of instrumentation, either on-line or by integration. Besides measurement of local irradiation conditions (fast and thermal neutron flux, coolant temperature and pressure, stress applied to experimental load etc.), behavior of sample is monitored thanks to specific sensors measuring on-line important parameters for models and codes. However it presents a lot of constraints such as miniaturization, robustness, adapted measurement range with requested accuracy, negligible drift, materials compatibility etc. which can cause technical issues for long duration experiments. Some of these issues can be overcome by equipping with lines either the sample (internal free volume…) or the surrounding connected volumes (coolant pipe, gas gap…). Their role is to collect and route the fluids to specific out-of-pile measurement means which monitor by on-line and delayed techniques specific chemical elements and isotopes released by the sample: fission products, fissile material, activation or corrosion isotopes or molecules, either in normal conditions (high demanding conditions, power transients, innovative coolant chemistry, first barrier loss…) or during safety tests with sample damage (loss of coolant, power injection…). This paper presents the interest of such measurements for supporting the development process of nuclear fuels and materials. Relevant design data for implementation on experimental samples are given. Analysis equipment recommended to be installed in the Fission Product Laboratory and the Chemistry Laboratory of the Jules Horowitz MTR, for activity and for atoms counting, are presented. Such laboratories are underlined as a key service offered by a modern multipurpose irradiation infrastructure

Rydberg electron capture mass spectrometry of some environmental pollutants

International audienceThis work relates a coupling between a Rydberg electron capture (REC) source and a mass spectrometer (MS) using a quadrupole ion trap within a special operating mode. The MS instrument is only briefly described as it has already been published. The advantages of the REC are shown, i.e. no fragmentation of the molecule occurs during charge exchange with the Rydberg xenon atoms. The molecular ion lifetime seems to be sufficient to perform mass spectrometry by Fourier analysis. The experiments concern certain molecules of interest in the field of the environment having a positive electron affinity to insure Rydberg electron capture, i.e. certain polyaromatic hydrocarbons, certain polychloro-biphenyls, and one dioxin. (Int J Mass Spectrom 189 (1999) 181–188