A study of the formation of cluster ions from inorganic solids using coincidence counting mass spectrometry /
Desorption mass spectrometry (MS) is an useful tool for the
| Main Author: | |
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965981&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Desorption mass spectrometry (MS) is an useful tool for the compositional analysis of solid surfaces. The use of MS to characterize the structure of solid surfaces is hindered by an incomplete understanding of the secondary ion formation processes. In particular, the predominant formation mechanism responsible for secondary cluster ion formation is still in question. Two models exist to explain the cluster formation process. One is based on gas phase recombination of non-adjacent atoms. The other model assumes that clusters are intact portions of the solid, providing structural information about the surface region. Coincidence counting and plasma desorption mass spectrometry were used to studv the cluster ion formation from a suite of inorganic solids. The primary objective was to determine the extent to which a secondary cluster ion represents the composition and structure of the original solid. A secondary objective was to determine the extent to which chemical factors such as: bond strength, oxidation state, and short and long range crystal order of the solid affect the formation and composition of secondary cluster Ions in PDMS. Based on direct comparison, the negative cluster ion compositions reflect the original solid whereas the positive ion compositions do not. A high degree of recombination is evident in positive ion formation. The formation of cluster ions is therefore attributed to different mechanisms. In general, negative clusters are formed by intact emission and positive clusters by recombination. The formation of intense recombination based positive clusters suggest a plasma reaction induced by the fission fragment. The negative cluster Ions also reflect back to the crystal structure of organized solids. The positive cluster ions do not. Changing the crystalline state of the solid while keeping the composition constant affects the formation of negative cluster ions. Large cluster ions are formed only from solids with a high degree of crystalline order. Using the yield of negative cluster ions in coincidence with a sample representative ions, it is shown that the transition of a solid from the gel to crystalline state can be monitored with MS. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xvii, 173 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |