Static Mass Spectrometer Research Articles

Dynamics of Hydrides on Hydrogen-Terminated Silicon (111)−(1×1) Surface

X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometer (SSIMS) have been applied to characterize Si(111) surface treated with 40% NH4F solution. As-treated Si(111) surface is predominately terminated with monohydrides and free of contamination. The dynamics of etching process on ultra-clean atomically flat hydrogen-terminated Si(111) surface in 40% NH4F solution has been examined at various potentials including the open circuit potential (OCP) by using in situ electrochemical scanning tunneling microscopy (ECSTM). Two distinct mechanisms are observed: (1) dihydride terminated step silicon atoms are dissolved much faster than the defect-free monohydride terminated ones; (2) dihydrides in the corner of {110} zigzag enclosed characteristic triangular pits lead to fast erosion of silicon atoms. Our results explain dynamic mechanics in formation of triangular pits on atomically flat silicon (111) surface in solution.

Helium and neon implantation and memory observed in a quadrupole mass spectrometer

High accuracy static quadrupole mass spectrometer (QMS) measurement of helium and neon may be impaired by implantation and long lasting thermal desorption effects of the previously trapped atoms. A QMS produces only moderately accelerated ions of 100–200 eV. The ions decelerate at stainless steel surfaces somewhere in the QMS and a part of them will be trapped in surface near sites. For helium and neon most of these trapped atoms are able to desorb with time constants of several hours. This causes an memory effect which hinders high precision measurements. The trapping and desorption experiments reported here indicate that these time constants for the desorption are about 90–477 min for temperatures between 330 and 470 K. 20–60% (330 K) and 450% (470 K) of the atoms which have been trapped desorb subsequently. This could be explained by assuming self-sputtering processes. From the desorption behaviour a binding energy of 1.1 and 1.6 eV for these atoms has been estimated.

Nitrogen and Argon Isotopes in the Archaean Continental Crust: Investigating the Evolution of the Early Earth

Tracing the origin and fate of major volatiles, such as nitrogen, it is important to understand the evolution Of the early earth. However, the geochemical behaviour of N is still poorly constrained and the resulting N evolution model of the earth is rather complicated. The general view supposes a mantle source with N being depleted in heavy isotopes (8~5N -25%0) and its degassed product (atmosphericcrustal N) and the residual mantle both enriched in heavy isotopes (815N from 0%0 to +12?tf=Pi2>%). To reconCiliate this paradoxical view, two diverging models Of the earth evolution have been proposed: (1) an original N source from enstatite chondrite (81SN -25%0) mixed with a tardive veneer (815N +42%o) recycled in the mantle by subduction (Javoy, 1997); or (2) the fractionation, due to atmospheric escape, of an enstatite chondrite original source (Marty and Humbert, 1997). These hypotheses need to be verified by measuring the N isotopic composition in the early earth, particularly in the Archaean crust. Until now, sparse data were available (e.g. Sano and Pillinger, 1990). The aim of this ongoing study is to obtain precise isotopic N data from the Archaean crust. We selected (1) 3.5-2.4 Ga cherts from Pilbara Craton and Hamersley Basin, Western Australia, rocks that have been neVer metamorphosed above the pumpellyte-prehnite facies (~250~ and (2) 3.8 Ga cherts and BIF (Banded Iron Formation) from Isua, West Greenland, metamorphosed to amphibolite facies (-600~ The choice of measuring N isotopes in the lsua samples was mainly dictated by the need to investigate: (1) the efficiency of N retention in Subduction-related recycling; and (2) whether N primordial compOnents have been preserved or not from high grade metamorphism processes. Nitrogen was extracted using a stepwise combustion technique, whose isotopic ratio was measured by a static type mass spectrometer, together with argon isotopes and carbon amount. Calibration of N relative to argon isotopes has been proven to be effective in deconvoluting N sources in rocks (Yamamoto et at., 1998). First results showed two volatile fractions in the Archaean sediments, released at 500-900~ and at 1000-1200~ respectively. The N amount was low (0.05-1.7 ppm) and it was accompanied by tow 36Ar contents (0.2-2 x 10 -14 mole/g), but high C contents, from 11 up to 3t00 ppm. The 615N values ranged from -5%o to +19%o. The 4~ ratios ranged from 300 to t9,000. Electron microprobe analysis and literature data gave K contents of 20-2000 ppm, low, but theoretically sufficient to produce the high 4~ ratios. This point is to be confirmed by ICP-MS analysis of K to decipher if the

Errors in measurements of atomic masses

The methods of measuring the atomic masses of stable isotopes with high-resolution static and dynamic mass spectrometers are examined. The typical measurement errors characteristic of both classes of devices are indicated. The greatest difficulty arising in such experiments is taking account of the effect of stray electric fields on the parameters of the motion of two types of ions forming a mass doublet as well as determining and introducing corrections for the corresponding errors in the measured mass values. This effect could be especially important in measurements of wide mass doublets. A method similar to the one employed in direct measurements of the magnetic moment of the proton in terms of nuclear magnetons with a magnetic resonance mass spectrometer with a two-section ion source is suggested for taking into account the effect of the stray electric fields in atomic mass measurements.

Combined Isotopic Analysis of Nanogram Quantities of Atmospheric Methane

Stable isotope measurements are increasingly utilized to constrain global budgets of atmospheric trace gases. Published analytical techniques for studying the parallel stable isotopic composition of methane (δ13C and δD) require prohibitively large quantities of methane for analysis. In a break from convention, a static mass spectrometer has been developed to use aliquots of methane as the analyte. These measurements yield the relative abundances (δ17M, ‰) of the major isotopomers of methane (13CH + 4 and 12 CDH + 3 ) with 12 CH + 4 . Analyses of 0.5 nmol samples of NGS standards have shown that δ 17 M can be determined with a precision of ±0.2‰. If the δ 13 C of the sample is known then δD may be calculated from the measured δ 17 M. Calculations show that a precision of 0.2‰ for δ 17 M is equivalent to measuring δD with a precision of ± 3.6‰ (cf. ±2–3‰ by conventional means). Where δ 13 C is not known, then δ 17 M still provides useful information on methane sources, in effect combining δ 13 C and δD.

Electron stimulated desorption of alkali metal ions and atoms: Local surface field relaxation

Electron stimulated desorption (ESD) of neutral alkali metal atoms and positive ions has been studied from alkali metal layers adsorbed on oxidized and silicided tungsten by means of a static magnetic mass spectrometer combined with a retarding field analizer. The desorbed alkali metal atoms were ionized in a surface ionization detector and their energy distributions were measured using a time-of-flight method. The ESD cross sections and energy distributions for alkali metal atoms and ions have been measured as a function of the incident electron energy and the deposited alkali metal concentration. To interpret the results we have extended the Auger stimulated desorption model taking into account the surface Coulomb field relaxation and the ESD of neutrals.

Nitrogen isotopic composition of a gas-rich ordinary chondrite, ALHA-77216

Nitrogen abundance and isotopic composition in a gas-rich chondrite ALHA-77216 (L3 or H3) was measured in order to obtain an independent estimate of the average nitrogen isotopic composition of the solar system. Nitrogen, Ne and Ar were extracted, by a stepped combustion method, and measured using a static mass spectrometer. The cosmic ray exposure age based on the 21Ne abundance is about 35.3 ± 1.1 million yr. Isotopically heavy nitrogen is observed at 700–1100°C. The abundance in a bulk sample is 1.38 ppm with 0.61 ppb excess 15N, of which 0.17 ppb could be due to cosmogenic nitrogen. Heavy nitrogen is enriched in the metal phases compared with silicates. A δ 15N value as large as 174‰ was observed for a the 800°C step of a magnetic separate. The abundance ratio of nitrogen to solar type rare gases in this meteorite is higher than those in lunar samples. We suggest that the isotopically heavy nitrogen is of solar origin, but other possibilities (presolar and indigenous nitrogen) cannot be completely ruled out.

Laser assisted reflectron time-of-flight mass spectrometry

Pulsed-mode laser assisted ionization schemes are extensively used in connection with time-of-flight mass spectrometric techniques, particularly when large-mass, thermally labile molecules i.e. biomolecules, proteins, and DNA have to be analysed. Along with the high resolution accomplished with the introduction of the reflector fields, these techniques have received considerable attention, in particular due to their ability to record a mass spectrum over the whole mass range with each single pulse. It is also important to note that the ionization volume (the space in which ions are created) can be considerably larger than in static mass spectrometers and with essentially unlimited mass-range. Furthermore, the sensitivity of laser-assisted reflectron time-of-flight mass spectrometry can almost reach its physical limit (a few atoms or molecules). Many modifications of laser assisted reflectrons have been developed. The key differences reside, on the one hand in the methods employed to focus the times-of-flight of the ions on the detector, and on the other hand with the specific sources used. One can expect to witness in the near future an ever increasing interest in these techniques with a wide range of new applications in fundamental and applied science or technologies such as materials science, analytical chemistry, pharmacology, biochemistry and genetics, to cite only a few.

Ion?Molecule Reactions and Mobilities of SF3+ and SF5+ Ions in SF6 Gas

Positive ion-molecule reactions in 8F6 were studied in a static drift-tube mass spectrometer using electron impact at 100 eY as the ion source. The ratio of electric field strength to gas number density, E / N, was typically varied from 40-282 Td and pressure ranged from 0�1 to o� 8 Torr. The most important processes were found to be 8Ft + SF6 ---+ 8Ft + 8F6 + F2 and 8Ft + 8F6 ---+ (82Fg)+* ---+ 82Ft + F 2. The interaction potentials for the 8Ft and 8Ft ions in SF6 were also found by using the measured mobility data which were obtained using a pulsed-ion transit-time method. We found that the (12,4, a* = 0�1) core model was adequate to describe the mobility over the range of E / N studied. The zero-field reduced mobilities for 8Ft and 8Ft were determined to be 0�68 and 0�55cm2y-1 s- 1 respectively.

Drift-tube studies of SF 3+ and SF 5+ ions in SF 6 gas

Positive ion/molecule reactions in SF 6 were studied in a static drift tube mass spectrometer using electron impact at 100 eV as the ion source. E/ N (the ratio of electric field strength to gas number density) was typically varied from 70 to 650 × 10 −17 V cm 2 and the drift tube pressure was varied over the range 0.1–0.7 Torr. The most important processes were found to be ▪ and ▪ The rate constants for both reactions were measured over a range of center-of-mass kinetic energies from 0.05 to 0.45 eV. The data were found to fall well below the values predicted by the Langevin model. At 0.06 eV, the rate constants for reactions 1 and 2 were found to have values of 6 × 10 −12 cm 3 mol −1 s −1 and 3 × 10 −13 cm 3 mol −1 s −1 respectively. The zero-field reduced mobilities for SF 3 + and SF 5 + ions were determined to be 0.61 and 0.65 cm 2 V −1 s −1 respectively.

Application of high-sensitivity carbon isotope techniques— a question of blanks

The performance of a new carbon stable isotope static mass spectrometer over the sample size range 10 pmol to 1 nmol is reviewed with reference to standard data gathered over a year of operation. Specimens of known isotopic composition and zero enrichment tests suggest that the instrument is accurate to within±0.5‰ over the entire sample size range, with precision only becoming worse than∼±;1‰at< 80pmol. Efforts to obtain “blanks” compatible with the above performance are also reviewed. A procedure is available which controls the total blank in a stepped combustion, from room temperature to 1200°C, to 1 nmol; in the temperature range of most inserest for extraterrestrial samples (600–1200°C),⩽50pmol can be achieved. However, a real benefit of the new instrument is that isotopic compositions of the blanks can be accurately obtained, so allowing a proper assessment of its causes and a correction of sample data if desired.

Quantitative surface analysis of organic polymer blends using a time-of-flight static secondary ion mass spectrometer

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantitative surface analysis of organic polymer blends using a time-of-flight static secondary ion mass spectrometerPatrick M. ThompsonCite this: Anal. Chem. 1991, 63, 21, 2447–2456Publication Date (Print):November 1, 1991Publication History Published online1 May 2002Published inissue 1 November 1991https://doi.org/10.1021/ac00021a012RIGHTS & PERMISSIONSArticle Views144Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Determination of the abundance and isotope composition of nitrogen within organic compounds: a sealed tube technique for use with static vacuum mass spectrometers

A technique for the determination of the abundance and isotopic composition of nitrogen within organic compounds is described. It is intended for use with high-sensitivity static vacuum mass spectrometers. The accuracy of the abundance determination is +or-5% by weight and replicate delta 15N determinations of nitrogen for five organic compounds were all within +or-8%. The compounds selected contained nitrogen within a variety of organic structures and with different types of nitrogen bonding including -NO2, -NH2, C identical to N, C=N, and C-N. In no case were detectable amounts of nitrogen oxides formed during oxidation. Blank analyses suggest that meaningful N abundance and delta 15N determinations can be performed on materials containing greater than 20 ppm nitrogen by weight.

A proposed standard (PTFE tape) for static SIMS

AbstractThe requirements for a viable standard material for the assessment of the performance of static secondary ion mass spectrometers are discussed. PTFE (polytetrafluoroethylene) tape appears to be a suitable candidate for assessing the absolute sensitivities of the instrument for both positively and negatively charged species, as well as assessing the charge compensation ability for insulators. An experimental procedure is described and representative spectra obtained under well‐defined conditions are presented.

Preparation of sub-nanomole quantities of nitrogen gas for stable isotopic analysis

Describes a technique for the extraction and purification of sub-nanomole quantities of nitrogen for stable isotopic analysis. The procedures described are intended for use with a high-sensitivity static vacuum mass spectrometer such as that describes by Wright et al. (1988). It is essential that low nitrogen blanks are obtained during the sample treatment; it can be demonstrated that contributions of nitrogen from the extraction and subsequent gas handling procedures can be limited to as little as 0.021 nmol. Experiments are described to verify that species such as CO2, CO and CH4, which would otherwise interfere with the nitrogen isotopic measurements, can all be removed during the purification operations. A study of the difficulties which might be encountered if some nitrogen were converted to nitrogen oxides has also been undertaken. It is concluded that N2O would be totally decomposed to the elements during purification but nitrogen in the form of NO and NO2 is only partially recovered. A method for investigating whether nitrogen oxide production is a real problem during the analysis of geological samples has been devised. Some examples using the technique are presented.

Static secondary ion mass spectrometry analysis of polycarbonate surfaces. Effect of structure and of surface modification on the spectra

The positive and negative ion mass spectra of the surfaces of polycarbonate derived from bisphenol A and polycarbonate derived from the bisphenol of acetophenone, and of bisphenol A and the bisphenol of acetophenone are presented. The spectra were obtained with a time-of-flight static secondary ion mass spectrometer. Comparison of the spectra of the four mentioned compounds made it possible to deduce the structures of characteristic ions. The interaction of amines with the surface of polycarbonate derived from bisphenol A could be analysed in a very detailed manner with the aid of the negative ion spectra. Some aspects of the interaction of hydrogen and oxygen plasmas with this polymer are discussed with reference to the spectra. Chain scissions were one of the processes occurring during the plasma treatments.

Electron-stimulated alkali metal desorption from the oxygen monolayer-covered tungsten surface

Electron-stimulated desorption (ESD) of atoms and ions of Li, Na, and Cs from the oxygen monolayer-covered W(100) surface has been studied by means of a static magnetic mass spectrometer combined with a retarding field analyzer. The ESD cross section of the alkali metal atoms within the monolayer is shown to be independent of the concentration of the deposited metal and is (7±3)×10 −22 cm 2. The ESD cross sections of the Li +, Na +, and Cs + ions at low concentrations are (1.2±0.2)×10 −22, (4±1)×10 −23, and (6±1)×10 −25 cm 2, respectively, and fall off with increasing concentration. The electron energy threshold corresponding to the onset of ESD of the alkali metal atoms and ions is ∼25 eV. The ESD cross section ratio of the Li 6 + and Li 7 + ions is 1.2±0.1 for concentrations N<10 14 atoms/cm 2 and increases up to 1.4 for higher concentrations. The slope of the retardation curves increases as one goes from Li to Cs. The model involving oxygen ion local Coulomb field relaxation permits one to describe the ESD of alkali metals not only qualitatively, but quantitatively as well. It can be used to determine the effective charge of the oxygen, the lifetime of the oxygen excited state on the surface, and the ESD cross sections for the alkali metal ions. The concentration dependence of the ESD cross sections of the alkali metal ions originates from the metallization of adsorbed metal films.

Measurement of carbon stable isotopes at the nanomole level: a static mass spectrometer and sample preparation technique

A triple collector static vacuum mass spectrometer is described for the determination of carbon isotope ratios from 1*10-9 mol samples of carbon dioxide gas. The instrument is capable of providing a differential isotopic composition ( delta 13C value) with a precision (1 sigma ) better than 10/00/; furthermore, the long-term stability, assessed by an extended zero-enrichment test, is not worse than +or-1.30/00. Because of abundance sensitivity problems, caused by working at high source pressure, the best performance is obtained using a reference gas which is similar in isotopic composition to the sample under investigation. A low blank, stepped heating procedure is outlined for use in preparing samples for study in the instrument. Some examples of problems to which the machine has been applied are given.

A sodium-atom beam source for UHV surface investigations and industrial applications

A source of pure Na-atom beams obtained under ultra-high vacuum (UHV) by reduction of sodium tungstates and molybdates with zirconium is described. An efficient miniaturised effusion source is utilised. The reaction products and the emission characteristics of the sodium source are studied in UHV using a static magnetic mass spectrometer. Comparison is made with other sources intended for the preparation of sodium layers in UHV.

Preparation of nanogram quantities of deuteromethane for stable carbon isotope analysis

Precise carbon isotope analysis at the nanogram level, using the static mass spectrometer, requires that sample carbon be in the form of deuteromethane. The authors describe the apparatus and technique for a low blank and quantitative deuteration reaction using a nickel catalyst for the conversion of carbon dioxide to deuteromethane. A regular relationship exists between the 12C/13C ratio for carbon dioxide measured conventionally at the microgram level and the m/z 20/21 ratio of CD4 produced from 7-24*10-9 g carbon aliquots of four samples of carbon dioxide whose carbon isotope compositions span most of the known natural abundance range.