Analysis of doubly-charged negative molecules by accelerator mass spectrometry

Abstract

Free doubly-charged negative molecules are a challenge for both theory and experiment. Their stability depends on a very delicate balance between interatomic structure, electronic interaction and Coulomb repulsion. Detecting di-anions of mass M with conventional mass spectrometry always bears the risk of erroneously measuring contributions from singly charged negative ions near mass M/2, or from molecular fragments with different energy. Another possible source of errors are mass ambiguities, e.g. M(12C4)≈M(16O3). In this contribution we show how one can overcome the methodical limits of conventional mass spectrometry by using AMS techniques for the analysis of very rare doubly-charged negative molecules. As an example, a new class of di-anions will be presented, (OCn)2−, n⩾5, which were discovered recently by secondary ion mass spectrometry, and were analyzed in detail by AMS.