We developed a memory efficient
algorithm for accurately calculating the isotopic fine structures of
molecules. Treating individual isotopic
species of a molecule as different mass states, we introduce the concept of
transitions between mass states and represent all mass states of the molecule
in a hierarchical structure. We show
that there exists a simple relationship between two different mass states at
two different levels of the hierarchical structure. This allows us to efficiently and accurately
compute both the mass and the abundance of every mass state of a small to
medium-sized molecule, whose gross structures include small number of fine
structures. A truncated calculation of
this algorithm can be applied to calculate a majority of isotopic species
(99.99% of cumulative abundance) of a large molecule.
Click here to download the programs IsotopeCalculator.