A new method of spectra acquisition and exact mass determination of resolved peaks in high mass resolution ion microscopy

Abstract

AbstractA major problem in high resolution mass spectrometry of solid materials has been the difficulty or even the impossibility associated with identifying the resolved peaks, i.e. the determination of their exact mass. A method of exact mass determination (relative precision in the range of 10−5) of resolved peaks is presented which requires no foreknowledge of the specimen. The method is derived from mass spectrometry techniques commonly employed for the analysis of liquid or gaseous organic samples, and is based on three steps: (1) the use of an external reference sample; (2) sequential analysis of the reference and unknown sample; and (3) superposition of the two spectra. The technique is illustrated using a standard CAMECA IMS 3f ion microscope.A further advance has been the development of single ion sensitive mass spectrography, where the entire spectrum within a narrow mass range is simultaneously viewed in real time. Spectra acquisition times are reduced by a factor of up to ten. Mass spectrography allows the detection of transient peaks or peaks of rapidly varying intensity, e.g. thin surface films or oxides. Using an image processor the spectra may be integrated or averaged in real time before storing in memory. Real time spectra acquisition and interpretation make high mass resolution SIMS (indispensable in material science) a routine operation providing information otherwise difficult or impossible to obtain.