While most ToF mass spectrometers utilize a multiple reference method, we have developed an anlysis technique utilizing a single reference species. This greatly simplifies the operation, as it is easy to introduce a single reference species, but much more complicated to introduce a pair of reference species.
The analysis relies on a reasonably known value for the offset between the start of the TDC clock and the actual ejection of ions. This value can be measured directly to be 30-50 ns. When the precision of the measurement requires a more exacting value, it can be extracted from high-statistics measurements of two distant references, such as 133Cs-85Rb or 133Cs-208Pb. With knowledge of this offset, the data analysis mimics that of Penning traps.
Using this analysis method, we have managed to demonstrate an accurate relative precision of 3x10-8 using isobaric doublets and 1x10-7 using non-isobaric external references. This is a level a precision on par with the venerated Penning trap mass spectrometers.
In many cases, one or more chain of isobars will be present in a spectrum. In such a case, the reference ion is useful for identification of the members of the chains, while precision mass ratios can then be made among the isobars. In this way, the MRTOF can analyze many isotopes simultansouly — combining the best features of Penning traps and storage rings!
