m - FWHM) for linear systems of any reasonable flight path length.
An alternative is to correct at source by allowing the ions to form in a field free region and then to apply the extraction field after an appropriate delay time. This pulsed or time-delayed extraction (tDE) allows the ions to develop their initial energy spread to such an extent that those ions with excess energy will have travelled far enough in the delay time to experience less of the extraction field than those ions with an energy deficit. If the delay time and extraction voltage are co-ordinated there will be an energy correction function applied to the ions. The full benefit of this correction will not be valid for the whole spectrum at once but can produce significant improvements in resolution over a given mass range.
Additionally, with time delayed extraction (tDE) there is time for fragmentation to occur before the ions reach the field free region. These ions produced by an in-source decay process (ISD), sometimes called prompt fragments, can therefore be seen in the spectrum.
Results from a Kompact MALDI IV-TDE fitted with both tDE for ISD and a curved field reflectron to allow seamless post source decay (PSD) show that there are significant differences between ISD and PSD spectra of the same sample.