Abundances and Dead Time

A mass spectrum is a chart of ion abundances versus m/z values. It is shown above that the TDC measures ion arrival times, which are converted directly into m/z values. Notionally, the number of ions arriving at the detector at any one m/z value is equal to the number of events recorded (one 

Example of a mass spectrum showing the peaks (or lines) corresponding to ions measured at various mlz values by the spectrometer the heights of the peaks relate to the abundance of the ions. 

The first ionization step in the source converts neutral molecules (M) into ions (M+). After a short time in the source, some molecular ions have fragmented to give smaller ions, F, ,, F/, along one or more reactions pathways. An ion (F, ) 

Perhaps it is worth emphasizing that the actual metastable ions are those that decompose, and the so-called metastable ions that are recorded are actually the products of decomposition, not the metastable ions themselves. It is more accurate to describe tlie recorded metastable ions as ions resulting from decomposition of metastable ions. The apparent m/z value of a metastable ion provides the link between an ion that fragments (the parent or precursor ion) and the ion that is formed by the fragmentation (the daughter or product ion)i 

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