The catalog of Bearden[9] provides the energies of the characteristic lines of the
target elements. The volume emissivity for the production of the spectral lines is calculated
using the electron collisional ionization cross sections for the parent atomic (sub)shells,
combined with the
specific line transition probabilities and the local electron flux density. The ionization
cross sections are those tabulated in the Livermore Evaluated Electron Data Library[11],
fit to a simple function of
electron energy. The line transition probabilities are derived from the radiative rates of
Scofield[13] and the nonradiative rates of Chen, Crasemann, and Mark[14],
or in the case of ionizations from shells 
M from the Livermore Evaluated Atomic
Data Library[12]. Some
transition probabilities are also estimated from the radiative yields compiled by
Krause[16].