Practical Electron Microscopy and Database

The L family of characteristic X-rays observed by EDS involves L_α(1), L_β1(0.7), L_β2(0.2), L_β3(0.08), L_β4(0.05), L_γ1(0.08), L_γ3(0.03), L_λ(0.04), and L_η(0.01). Different from the K-family, the numbers in the parentheses present approximate relative intensities, since these intensities vary with the over-voltage and with the element in question .

If neither a proper database nor standards are available, the k_AB factors can be theoretically calculated,
            ----------------------------- [2519]
where,
          Q_A and Q_B -- The ionization cross-sections for the X-rays of elements A and B, respectively,
          w_A and w_B -- The fluorescence yields for elements A and B, respectively,
          a_A and a_B -- The relative transition probabilities for elements A and B, respectively,
          A_A and A_B -- The atomic weights for elements A and B, respectively,
          ε_A and ε_B -- The detection efficiencies of the EDS detector for the X-rays from elements A and B, respectively.

In Equation 2519, it is most difficult to accurately calculate Q and ε. The extraction of the k_AB values for K lines above 1.5 eV in energy is in error of ~10 to 15% mainly due to the inaccurate estimation of Q. For the same reason, it is not recommended to calculate the k_AB values for light elements Z < 11 or for L lines.