Loadable Function: a = FluorYield (Z, shell)

Fluorescent Yield

          Z : atomic number
          shell :
          K_SHELL  0
          L1_SHELL 1
          L2_SHELL 2
          L3_SHELL 3
          M1_SHELL 4
          M2_SHELL 5
          M3_SHELL 6
          M4_SHELL 7
          M5_SHELL 8