The study of cluster ion formation from inorganic solids using time-of-flight mass spectrometry /
Plasma desorption mass spectrometry was used to characterize
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739668711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Plasma desorption mass spectrometry was used to characterize and compare the distributions of cluster ions produced from a variety of inorganic metal-oxygen systems: oxides, nitrates, sulfates and carbonates. This fundamentally and analytically relevant study, was principally aimed at providing insights into the general patterns of the cluster ion formation process. A secondary objective was to determine the influence of the chemistry and arrangement of constituent atoms on the composition, distribution and abundance of cluster ions. Metal-oxide based clusters are predominant in the positive spectra with qualitatively similar distributions for metal-oxygen systems with a common cation, irrespective of their anion stoichiometry. The stoichiometries and relative abundances of these clusters are interpreted in terms of their chemical and structural constitution. The negative clusters observed reflect, to a greater degree than the positive clusters, the stoichiometry and molecular composition of the original solid. The observed positive cluster species are considered evidence of a localized plasma state created by MeV ion impacts; while the negative clusters are consistent with a relatively intact emission process occurring further from the nuclear track created by the impinging fast heavy ion. The periodic cluster abundance enhancements observed for compositions such as (BaO)nH+ and (BaO)nBa+, are coherently rationalized on the basis of ionically bound three-dimensional nanostructures reminiscent of portions of the fcc condense oxide lattice. These exceptionally stable clusters are also correlated to anomalously low metastable fractions. Cluster abundances and extent of clustering from oxy-anion metal salts are generally greater than that from the metal oxides. This observation is attributed to the disparate sample metal-oxygen ratios and the enriched oxidizing environment that seemingly promotes greater cluster aggregation and growth. Cluster stabilities and distributions are generally guided by the ionicity of the metal-oxygen bond, the oxidation state of the metal, and their propensity to unimolecular decay. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xv, 119 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 110-118. |