The observation of metastable transitions in a double-focussing mass spectrometer using a linked scan of the electric sector and magnetic sector fields

Abstract

A detailed study has been made of the observation of metastable transitions in the first field-free region of a double-focussing mass spectrometer of Nier—Johnson geometry by scanning simultaneously the magnetic field B and the electric sector field E such that B/ E remains constant throughout the scan. The B/ E linked scan provides a convenient method of determining the daughter ions formed from a chosen parent ion and, because of the transmission characteristics associated with this type of scan, sharp peaks are observed irrespective of the amount of internal energy released as translational energy of the fragments. This greatly facilitates the accuracy with which the mass ratio of parent and daughter ion can be determined and also allows a wide range of mass ratios to be investigated at full source sensitivity. The scan gives equally good results when used to study collision-induced decompositions. The origin of several low-intensity artefact peaks is established and methods of recognising such peaks are discussed. The B/ E linked scan complements other methods of investigating metastable transitions already in use and is likely to find most application in the study of analytical problems.