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Detection of Large Cluster Ions by Ion‐to‐ion Conversion
Author(s) -
Nguyen VanTan,
Wien K.,
Baranov I. V.,
Novikov A. C.,
Obnorskii V. V.
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(199609)10:12<1463::aid-rcm690>3.0.co;2-0
Subject(s) - chemistry , ion , analytical chemistry (journal) , kinetic energy , cluster (spacecraft) , fission , range (aeronautics) , atomic physics , nuclear physics , materials science , physics , neutron , chromatography , organic chemistry , quantum mechanics , computer science , composite material , programming language
Gold cluster ions in the mass range of 4×10 4 –2×10 6 u were produced by bombarding a thin film of gold with 252 Cf fission fragments. The gold film which covered a carbon–aluminium substrate formed islets having a mean diameter of 44 Å. It turned out that nearly each second fission fragment penetrating an islet desorbed this islet as a whole. Most of these desorbed gold grains were negatively charged. They were investigated by means of a tandem time‐of‐flight (TOF) instrument. In the first TOF section, the cluster ions gained a kinetic energy of z×40 keV (where z is the charge state) and hit a converter, from where secondary ions and electrons were ejected. The most efficient converter material found so far is cesium iodide which particularly emits Cs + , I − and cluster ions. Less efficient were the contaminated or clean metals Au, Ag, Cu and Pb and the alloy AgMgO. At an energy of z×40 keV, the mean secondary electron yield from CsI was 0.011 per cluster ion. The detection efficiency for a cluster ion by ion‐to‐ion conversion was found to decrease from 99.7% to 96.5% in the available mass range. After correction for detection efficiency the complete mass‐to‐charge distribution between 4×10 4 and 2×10 6 u/z was determined and compared with a corresponding mass distribution of the gold‐islets covering the substrate. The mean charge state of the negatively charged clusters was estimated to be 1–2 and the mean mass z×295 000 u.