Tools and Procedures for Quantitative Microbeam Isotope Ratio Imaging by Secondary Ion Mass Spectrometry

Published

July 1, 2003

Author(s)

John G. Gillen, David S. Bright

Abstract

In this work we demonstrate the use of secondary ion mass spectrometry (SIMS) combined with the Lispix image processing program (Bright 1995) to generate quantitative isotope ratio images from a test sample of a calcium-aluminum rich inclusion (CAI) from the Allende meteorite that is known to contain discrete mineral grains with perturbed Mg isotopic ratios. Using 19.5 keV impact O- primary ion bombardment and detection of positive secondary ions, microbeam imaging SIMS has allowed us to identify, from the isotope ratio images, enrichments in the ²⁶Mg/²⁴Mg isotope ratio of approximately 5 % to 15 % in selected mineral grains. Using custom image processing software, each isotopic ratio image is corrected on an individual pixel basis for a number of factors including detector dead-time, mass bias effects, and isobaric interferences. We have developed procedures for correlating the isotopic images with polarized optical microscopy so that targeted mineral grains could be identified for further SIMS analysis. Finally, additional image processing tools have been developed to allow for pixel-by-pixel evaluation of the influence of detector dead-time and count rate errors on the isotopic ratio images and for correlation of the isotopic images with elemental distribution maps.

Citation

Scanning

Volume

25

Issue

No. 4

Pub Type

Journals

Keywords

image processing, isotope ratio, isotope ratio imaging, secondary ion imaging, secondary ion mass spectrometry, surface analysis

Citation

Gillen, J. and Bright, D. (2003), Tools and Procedures for Quantitative Microbeam Isotope Ratio Imaging by Secondary Ion Mass Spectrometry, Scanning (Accessed December 12, 2024)