Mass Spectrometric Observation of Doubly Charged Alkaline‐Earth Argon Ions |
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Authors: | Dr Bodo Hattendorf Bianca Gusmini Dr Ladina Dorta Prof?Dr Robert S Houk Prof?Dr Detlef Günther |
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Institution: | 1. Laboratory of Inorganic Chemistry, ETH Zurich, Zurich, Switzerland;2. Solvias AG, Kaiseraugst, Switzerland;3. Ames Laboratory U. S. Department of Energy, Department of Chemistry, Iowa State University, Ames, IA, USA |
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Abstract: | Doubly charged diatomic ions MAr2+ where M=Mg, Ca, Sr or Ba have been observed by mass spectrometry with an inductively coupled plasma ion source. Abundance ratios are quite high, 0.1 % for MgAr2+, 0.4 % for CaAr2+, 0.2 % for SrAr2+ and 0.1 % for BaAr2+ relative to the corresponding doubly charged atomic ions M2+. It is assumed that these molecular ions are formed through reactions of the doubly charged metal ions with neutral argon atoms within the ion source. Bond dissociation energies (D0) were calculated and agree well with previously published values. The abundance ratios MAr+/M+ and MAr2+/M2+ generally follow the predicted bond dissociation energies with the exception of MgAr2+. Mg2+ should form the strongest bond with Ar D0 (MgAr2+)=124 to 130 kJ mol?1] but its relative abundance is similar to that of the weakest bound BaAr2+ (D0=34 to 42 kJ mol?1). The relative abundances of the various MAr2+ ions are higher than those expected from an argon plasma at T=6000 K, indicating that collisions during ion extraction reduce the abundance of the MAr2+ ions relative to the composition in the source. The corresponding singly charged MAr+ ions are also observed but occur at about three orders of magnitude lower intensity than MAr2+. |
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Keywords: | alkaline earth metals inductively coupled plasma mass spectrometry mass spectrometry molecular ions noble gases |
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