Metastable ion intensities and the comparison of ionic structure

Abstract

The theoretical basis for comparing the structure of reacting ions by measurement of the relative abundance of metastable ions is examined. It is shown that except for those reactions whose rate constants are of the form kn(E) = Kng(E) there may be some variation in the metastable abundance ratio for reactions of ions of the same structure derived from different origins. The variation can arise because of different energy distributions of precursor molecular ions and different rates of formation of fragment ions. For reactions arising from separate states (or structures) of an ion, the metastable abundance ratio determined for different origins of the ion will be markedly dependent on the energy distribution of the molecular ions. In these cases, the consideration of more than one metastable abundance ratio can indicate which reactions arise from states which are common to all origins of the reacting ion.

Metastable ion characteristics. XXII. Collisional activation spectra of organic ions

“…Figure12. Estimated P(E)" function for phenol molecular ions at electron energies of (O) 50 eV, ( ) 20 eV, and (X)11 eV. Figures within the circles are the masses of the product ions utilized (see text).…”

Relative intensities of metastable peaks measured with B/Elinked scan and metastable defocusing techniques

“…The decrease in the A values for compounds with R' = H (1-3) can be explained by the redistribution of energy between charged and neutral species on decomposition of M + ions. 15…”

Using model ionization efficiency curves to evaluate the methods for determining appearance potentials

“…Evidence for isolated reacting states has been presented previously. 18 The resultant ionization efficiency curve derives from addition of the ionization efficiency curves due to each reacting state. If the lower energy reaction is a minor one (-1 %), the net ionization efficiency curve will show 'tailing' and the critical slope for the major reaction may not be attained.…”