Polyatomic ion beams

Ada ET, Kornienko O and Hanley L (1998) Chemical modification of polystyrene surfaces by low-energy polyatomic ion beams. Journal of Physical Chemistry B 102 3959. 

A time-of-flight mass analyzer (TOF-MS) does not depend on a magnetic, electrostatic, or RF field to disperse or filter ions for individual m/z ion detection. A pulsed polyatomic ion beam is accelerated to a constant kinet-... 

With the extension of FIBLAS to polyatomic molecular ions, it becomes obvious that the combination of mass spectrometry and "in flight" optical diagnostic (eventually at very high resolution) offers unprecedented opportunities in molecular structural analysis via isotope labelling and optical isotope (or isomer) shift measurements. Infrared photodissociation which has already been observed in several polyatomic ion beams " may have the power to turn the entire scheme into a much needed very high sensitivity analytical tool. 

Today, secondary ion mass spectrometry (SIMS) is frequently used for analysis of trace elements in solid materials, especially in semiconductors and in thin films [62,63]. Primary beam species useful in SIMS include Cs+, Oj, O, Ar+, and Ga+ at energies from 1-30 keV. The bombarding primary ion beam produces monatomic and polyatomic particles of sample... 

Figure 6.8 Interference problem in SIMS polyatomic ion formation by sputtering of borophosphosilicate glass using an 02+ primary ion beam. (R. C. Wilson, F. A. Stevie and C. W. Magee, Secondary Ion Mass Spectrometry (1989). Reproduced by permission of John Wiley Sons, Inc.)...

Investigations of cluster formation serve to explain the evaporation and atomization of sample material and ion formation processes. A further aim of cluster research is to find out under what conditions cluster or polyatomic ion formation can be influenced in order to avoid disturbing interferences and decrease the detection limits of elements. On the other hand, polyatomic ions have also been used as analyte ions for analysis, e.g. the application of MCs+ and MCs2+ dimeric and trimeric ions as analyte11 or of cluster primary ion beams (e.g., of bismuth and gold primary clusters)15 16 by the bombardment and sputtering of a solid surface in SIMS.17-21 Especially in SIMS, a multitude of cluster ions with high ion formation rates are observed.18 22 23... 

The difference between a DRC and a CC ICP-MS is that a reaction cell uses a Q mass spectrometer with a defined stability region, allowing the rejection of a defined mass region from the ion beam, whereas a CC uses a hexapole or octapole mass spectrometer as an ion guide. DRC have no limit on the gas type used, whereas CCs can only use inert gases or a simple reactive gas such as He or H2. Limits of detection (LoDs) for As are 0.01 ng l-1. However, LoDs can only be achievable with careful control of contamination and minimization of polyatomic interferences. Arsenic LoDs may be improved by the introduction of the element into the ICP-MS in the gaseous form, for example, by formation of ASH3, which markedly improves the LoD as nearly 100 percent of the analyte in solution reaches the mass detector. 

A decade ago, while considerable data had been compiled on the kinetic measurement of dissociative recombination (DR) reactions of small polyatomic ions, laboratory information on the product distributions of such reactions was restricted to the results of a few merged-beam and stationary-afterglow studies on DR of C02 and of H( [157,158], and the first explorations of combined flow tube/Langmuir probe/spectroscopic detector techniques, independently pursued by Rowe and co-workers (at Rennes) [159,160] and by Adams and co-work-ers (at Birmingham, and subsequently Atlanta) [161, 162]. Considerable advances have since been made, both in measurement of recombination coefficients (particularly for larger ions) and in the elucidation of product distributions for a still small but growing sample of important IS ions. 

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