[Big-Daddy]

Given a certain ion which, in all its isotopomers, is to be analysed in a mass spectrometer, is there a way - besides listing out all of the isotopomers and calculating their M_r values one by one - to find the M_r values for all the different peaks we expect for that ion? We're only talking about isotopic patterns here, fragmentation is not the concern.

For instance, I deduced we can find the number of isotopomers of the ion in question from 1) the number of atoms of each element in the ion and 2) the number of isotopes of each element which is present in the ion. It is simply the product over all elements of combinations with repetition allowed (N_c=(n+r-1)!/(r!·(n-1)!) is the combinations with repetitions formula). This suggests to me that, with these 2 pieces of information for each element in the ion, and 3) the A_r of every isotope of each element present in the ion, we might be able to show how to list all of the Mr values we expect peaks for, without having to write out the whole ion again and again?