Internal energy effects on metastable characteristics. The structure of [C3H7O]+ ions

The effect of changes in the internal energy distribution of the fragmenting ion on the ratio of metastable ion intensities for two competing fragmentation reactions has been investigated both theoretically and experimentally. Model calculations have shown that if the competing reactions have significantly different activation energies the metastable intensity ratio does depend on the internal energy distribution although large changes are necessary before the ratio changes by more than a factor of two. Experimentally the metastable characteristics of [C3H7O]+ ions of nominal structures [CH3CH2O+CH2] (I), [(CH3)2CO+H] (II), [CH3CH2CHO+H] (III) and [CH3O+CHCH3] (IV) have been examined. For each structure the metastable characteristics are found to be distinctive and independent of changes in the internal energy distribution of the fragmenting ion where these changes result from altering the precursor of the [C3H7O]+ ions. It is suggested that these internal energy changes can be estimated from the fraction of [C3H7O]+ ions which fragment in the ion‐source. It is concluded that structures I to IV represent stable and distinct ionic structures.