The ratio of ‘metastable peak’ abundances in relation to the question of decomposition from isolated electronic states in electron-impact mass spectra
Abstract
‘Metastable peaks’ for the loss of DCN and HCN from the molecular ions of [2,4,6-2H3] benzonitrile and [2-2H1]-benzothiazole, and of OH and OD from the molecular ions of [2,4,6-2H3]benzoic acid, have been examined in two field-free regions of a double-focussing mass spectrometer of Nier–Johnson geometry. The ratios of the relative abundances of the ‘metastable peaks’ arising from the loss of the deuterium-containing and the deuterium-free neutral particles show a significant dependence on electron beam energy (and in representative cases, upon repeller potential and accelerating voltage). While there are indications in the literature that these results might be interpreted in terms of decompositions from isolated electronic states, it is felt that in the present instances the effective energy bands giving rise to decompositions in the ‘metastable regions’ are sufficiently broad to preclude any such secure conclusions.