Isotope effect in mass spectrometry

Taken as a whole, the literature on isotope effects in mass spectrometry exhibits two salient features. The values of isotope effects for different molecules and different experimental conditions vary greatly and the isotope effects for some decompositions are very large (>100). These isotope effects are based on ion abundances, as has already been emphasised, but the kinetic isotope effects if measured would show not dissimilar variety and magnitudes. Both features arise because the range of internal energies encountered in reactive ions is very wide and the isotope effects are dependent upon internal energy, usually increasing... 

The most fundamental chemical questions concerning the molecular weight, atomic co-ordinates and bond strengths of thiols have been answered in the most precise way by careful physical measurements of the translational, rotational and vibrational motions of thiols. Since in any one measurement the number of physical variables usually exceeds the observable parameters, meaningful physical parameters could not have been obtained if measurements had not been made on a series of iso-topicaUy substituted molecules. It is now common practice in molecular spectrometry to site a motional process from several isotopically labelled positions in a molecule. In the following sections, we will briefly describe the physical origin of the isotope effect in mass spectrometry, microwave... 

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