1. A method of calculating an electron resonance spectra data value for each of one or more chemical constituents, the method comprising: identifying one or more potential electron capture orbitals for each of the one or more chemical constituents; determining an electron orbital wavefunction for each of the one or more potential electron capture orbitals; and generating a theoretical electron resonance spectra data value for each of the one or more chemical constituents from the corresponding electron orbital wavefunctions.