The K X-ray productions for the Mg, Al, Ti, Cr, Cu, Zn, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb thin films, the L X-ray productions for the Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Ta, W, Pb, Bi targets and the M X-ray productions for the Ta, W, Pb, and Bi films were investigated using 44.8 MeV, 56 MeV, 67.2 MeV, 78.4 MeV and 89.6 MeV 56Feq+ accelerated beams. The obtained experimental data were compared with the PWBA and ECPSSR theoretical values calculated with the ISICS11 code. A sharp increase in the cross sections for the target elements close to iron is observed. In this way, the X-ray production cross section for the selected chemical element in the PIXE analysis can be maximized with the irradiation mode selection – the energy and species of the incident ion.