Source Mass Spectrometer Research Articles

A filament current regulator for solid source mass spectrometers

Filament current regulator for solid source mass spectrometers to study temperature dependence of alkali ion emission

A technique for ion-trapping in pulsed-source mass spectrometry.

A technique is described for trapping positive ions for periods up to 400 μs in the pulse operation of a mass spectrometer source.

Determination of Cosmic-Ray-Produced Titanium and. Vahadium in Iron Meteorites.

The concentration of cosmic-ray-produced stable nuclides of titanium and vanadium in iron meteorites, especially in the Grant meteorite, were determined by a surface ionization solid source mass spectrometer using an electron multiplier. A triple filament technique was applied for both elements. A rhenium ribbon was applied to the center(ionizing)filament and for titanium two tantalum ribbons and for vanadium tungsten ribbons to the side(sample)filaments respectively. Repeated experiments using 0.1-1 microgram quantity of reagent titanium and vanadium indicated a satisfactorily high reproducibility throughout the cource of this work. The results with the reagent titanium and vanadium were in a good agreement with the determinations by Hogg and by White et al respectively. Using about one gram of the iron meteorites specimen, the extractions of titanium and vanadium were performed simultaneously in a systematic wet chemical separation scheme with potassium, calcium, chromium, and manganese. For the determination of the absolute contents of cosmogenic nuclides, isotopic dilution analysis was made using enriched 46Ti for titanium and reagent vanadium for vanadium as the spikes. The determination of above nuclides were possible with sufficiently low contamination of natural elements at the levels of 0.1 ppm for titanium and 0.01 ppm for vanadium. The enrichment in 49Ti was observed most prominently in the mass spectrum of titanium samples separated from the iron meteorites. At the same time the other products, 47Ti and 46Ti were also determined with a high reproducibility. 50Ti was also measurable though the error, ±30%, was still high. Examples of the data of cosmic ray produced stable titanium and vanadium are as follows;[unit:×1013 atoms/g. of meteorite]Aroos: 46Ti 4.00, 47Ti 4.85, 49Ti 7.70, 50Ti 0.27, and 50V 5.45. We have completed a set of data at A=50which includes new data of 50Ti and 50V, and our previous data of 50Cr and also 50V.The distribution of these three isobars provides useful measure in the spallation systematics in meteorites. Two parameters, R and S, in the semi-empirical equation of spallation cross section, Inσ(Z)=-R(Z-SA)2+K, were calculated to be 1.5±0.2 and 0.469±0.001 respectively. The radiation age of Aroos was estimated applying widely ranged pairs of both radioactive and stable nuclides, which were now all available. Each age derived from different isobaric pairs agreed well and this may suggest the negligible effect of space erosion or similar mechanisms such as many small collisions in space. In Grant, the depth effect was found to be effectively negligible with 49Ti and 50V in contrast to lighter nuclides such as Ne and K. Any irregurality in a curve of spallation yield vs.ΔA was not observed in mass range of 46-49. The experimental procedure is described in detail.

Consecutive ionic reactions in propylene and cyclopropane

Ion-molecule reactions occurring in propylene and cyclopropane have been studied, up to a pressure of 0.9 torr, inside a mass spectrometric source where ionization is provided by tritium β-rays. Consecutive ion-molecule reactions leading to the formation of polymeric ions up to C13H+25 have been detected. The pattern of reactions appears to be similar in the two isomers.

Comments on the paper `A theoretical assessment of the possibility of selected-area mass-spectrometric analysis using a focused ion beam'

Some ion-probe source mass spectrometers which have been constructed, but are not referred to in Long's 1965 paper, are briefly mentioned. These embody certain features he discusses. In addition, mention is made of an interesting instrument that utilizes the neutral species produced by ion bombardment rather than the ions, and thereby achieves a considerable reduction of the differences in sensitivity from element to element observed in secondary-ion spectra.

�ber den massenspektrometrischen Nachweis von extrem kleinen Alkalimengen

Experiences are described with Geiger-counters for ion-detection in combination with a solid source mass spectrometer of the 600-sector field type and about practice of this apparatus for trace analysis of some alcali metals. The sensitivity for caesium has been found of the order of a few 10−19 g, while the high sensitivity of the method for the other elements seems to be of merely theoretical interest on account of the inevitable contaminations.

Isotopic analysis of lithium in the Holbrook meteorite and in terrestrial samples with a sputtering ion source mass spectrometer

The isotopic composition and the distribution of lithium have been studied in the Holbrook meteorites, in granite and in hornblende, using a sputtering ion source mass spectrometer of our own design. In granite and hornblende, the isotopic ratios obtained for all the points of the surface which have been investigated remain 12.0 within a ±2% uncertainty (uncorrected for mass discrimination).With exactly the same technique, the ratios obtained in Holbrook show fluctuations of about ± 10% around an average of 12.0.

Consecutive ionic reactions in gaseous butenes

Ion-molecules reactions occurring in the four isomeric butenes have been studied up to a pressure of 0.5 torr inside a mass spectrometric source, where ionization is produced by tritium β-rays. Long-chain processes have been recognized, leading to the formation of polymeric ions. In isobutene, the predominant chain, which involves alkyl carbonium ions, has been followed up to C16H+33. This chain, although with a lower yield, has also been found in the other isomers. Minor chains and branching reactions complicate the mass-spectra at the highest pressures investigated, and lead mainly to CnH+2n–1 and CnH+2n–3 ions. Peculiar to the 2-butenes are extensive chains of odd-electron CnH+2n ions.

Application of the MS7 solid source mass spectrometer to the analysis of iron and low-alloy steel

Standard samples of high-purity iron and low-alloy steel have been examined systematically on the AEI MS7 mass spectrometer with a view to determining the general levels of accuracy and reproducibility obtainable for impurities in the range 0.001 % to 0.1 %. Twenty-four elements have been determined in different samples by direct examination on the spectrometer and, with a few exceptions, the mean results were found to be in reasonable agreement with the nominal figures. Many elements gave coefficients of variation between 15% and 35% but certain elements such as sulphur, phosphorus, arsenic and lead showed larger deviations. Use of argon ion bombardment to clean the electrodes to reduce the inherent carbon blank and also to determine gas levels has been investigated. Results of the correct magnitude were obtained for nitrogen and carbon although with poor reproducibility. Blank values were not reduced sufficiently to permit any useful values for oxygen to be obtained.

782. Mass spectrometer source leading lock and isolation valve: R Munro and R G Ridley, Rev Scient Instrum, 36 (11), Nov 1965, 1538–1539

782. Mass spectrometer source leading lock and isolation valve: R Munro and R G Ridley, Rev Scient Instrum, 36 (11), Nov 1965, 1538–1539

Isotopic Measurement of Chromium Induced by Cosmic Rays in Iron Meteorites.

Stable chromium nuclides produced by cosmic rays were measured by the surface ionization method applied with a chromium fraction extracted from several iron meteorites. A solid source mass spectrometer, MS-5, manufactured by AEI, England, was used for the determination of theisotopic ratios. It was found to be useful to apply the single filament technique using a tungsten ribbon. Repeated experiments using a microgram quantity of reagent chromium gave satisfactory small deviation throughout the course of this work which extended more than one year. The result with the reagent was in good agreement with natural chromium isotopic composition that appeared in literature. A marked enrichment of 54Cr, 53Cr and 5050;Cr due to cosmic ray products could be observed in chromium isolated by solvent extraction from meteorite solutions. An isotopic dilution analysis using enriched50Cr or 52Cr was made to obtain absolute content of these cosmogenic nuclides. The overall contents of53Cr and 54Cr were found to be in the range of13-25ppb in several meteorites. The experimental procedure is described in detail here.

Electron bombardment ion source for isotopic analysis of solids

A compact arrangement is described which allows an electron bombardment crucible source system to be used in thermal ionization solid source mass spectrometers. It is possible to insert the electron producing filament, the ionization chamber and the crucible into existing vacuum locks designed solely for thermal ionization use. Modifications necessary to use this source on an AEI MS 5 mass spectrometer are described together with the minor changes to the existing filament supplies required to stabilize the total electron emission. Memory effects are very low and samples of nickel, tellurium, antimony, copper and cadmium can be isotopically analysed with less than 5 μg amounts.

The isotopic composition of terrestrial and meteoritic tin

The relative isotopic composition of tin extracted from 22 terrestrial samples, 4 iron meteorites, and the metal phase of 1 mesosiderite has been measured in a solid source mass spectrometer. No differences greater than 1% were found in the abundances of masses 116 to 124 or greater than 5% for masses 112 and 114 in any of these samples with respect to a tin standard.

473. A method of increasing the production of uranium ions in a mass spectrometer source: N. C. Fenner, J. Sci. Instrum., 41 (1), Jan. 1964, 48–49

473. A method of increasing the production of uranium ions in a mass spectrometer source: N. C. Fenner, J. Sci. Instrum., 41 (1), Jan. 1964, 48–49

Gas source mass spectrometry of trace leads from Sudbury, Ontario

The measurement of lead isotope abundances with a gas source mass spectrometer has been limited to lead ores and minerals. A free radical technique for the preparation of lead tetramethyl is described which has reduced by a substantial amount the sample size necessary for a precise gas source analysis. In this way, the range of minerals which may be studied by means of a gas source mass spectrometer has been greatly extended. The free radical method has been applied to the study of lead isotope abundance variations in the mining district of Sudbury, Ontario. The analysis of lead from various sulphides has yielded lead isotope ratios which are linearly related on a plot of Pb 207/Pb 204 vs. Pb 206/Pb 204 with a slope of 0.131 ± 0.003; the standard deviation of points from their best straight line is 0.37 per cent of the average Pb 207/Pb 204 value. (The intercomparison technique previously used by us to determine the ratios of ordinary leads was not used for these analyses.) It is concluded that the linear relationship is the result of just two geological events, which fact simplifies the possible interpretations. The maximum times of these two events are 21.30 ± 50 m. y. and 1280 ± 50 m. y. respectively. Two interpretations of the results are suggested. The first gives ages of 1950 and 350 m.y. for the primary and secondary events. The two events in the second interpretation are considered to have occurred 1600 and 950 m.y. ag. The second interpretation is more easily defended on geological grounds.

A method of increasing the production of uranium ions in a mass spectrometer source

The efficiency of a boat filament is increased by exposing the sample to a hot rhenium fllament in an atmosphere of hydrogen and oxygen at about 0.3 torr. Gains of three orders of magnitude were attained with samples of 10/sup -8/ g of uranium loaded as uranyl nitrate. This treatment is compared with a benzene treated boat and a triple filament over a range of sample sizes, and an explanation of the results is given. (auth)

The electric potential in the region of a thin slit

In the course of determining the potentials within a mass spectrometer source, simple rules have been discovered which aid the calculation of potentials about a thin slit. These rules, of which there are four, make possible the approximation with ruler and compass of the equipotentials formed by opening a long, narrow slit in a thin conductor separating regions of uniform electric field. A simple iteration formula is included which enables the approximate potential at any point to be refined to any desired degree. Proofs of these rules are developed with the aid of conformal mapping in the complex plane.

Effects of Isotopic Labeling and Molecular Structure on Probability of Ionization by Electron Impact

Isotope effects have been reported on probability of ionization of molecules by photons, by excited rare-gas atoms, and by beta rays. Such effects furnish evidence that ionization occurs largely as a secondary process in competition with nonionizing processes following primary excitation to an energy level above the ionization potential. Measurements of total ion current produced in a mass-spectrometer source show similar effects for the case of ionization by 70-V electrons. Experimental support has been obtained also for the corollary that probability of ionization depends upon molecular structure and is not simply, as has been postulated, a constitutive property of the atoms.

New mass spectrometer solid source arrangement for the simultaneous analysis of two samples

The filaments of the usual triple filament assembly used in thermal ionization solid source mass spectrometers have been rearranged to permit the analyses of two separate samples, on the same filament bead. One of these samples may be a standard. Smaller isotopic abundance differences can be detected using this new arrangement which confers on a solid source machine some of the advantages of a dual inlet gas machine. It also appears to have a somewhat higher efficiency for the production of ions. Experiments demonstrate the improvement in accuracy, and the absence of cross contamination provided certain precautions are observed.

Rates of electron removal by recombination, attachment and ambipolar diffusion in nitric oxide plasmas: R.C. Guntun and E.C.Y. Inn, J. Chem. Phys., 35 (5), Nov. 1961, 1896

A variety of closed shell hydrocarbon ions have been observed following charge transfer from Zn+ to isobutylene (C4H8) in a high-pressure mass spectrometric (HPMS) source. The time profiles of these ions and their strong pressure dependence suggest that consecutive and sequential ion-molecule reactions are responsible for their formation. The interaction of Zn+ with isobutylene clusters (C4H8)n generated by a supersonic beam expansion results in efficient generation of the C4H9(C4H8)n+ series. These observations suggest has phase and intracluster polymerization behavior induced by Zn+. Clusters provide a feasible and valuable approach for understanding the mechanism of the early stages of cationic polymerization.