M X-ray production cross-sections in

M X-ray yields of thin targets of 79Au and 83Bi in collisions with 50–300 keV protons have been measured. The production cross sections of Mζ[(M5–N3) + (M4–N2)], Mαβ[(M5–N6,7) + (M5–O3) + (M4–N6) + (M4–O2,3) + (M3–N2)], Mγ[(M3–N4,5) + (M2–N1)], Mm1[(M3–O1,4,5) + (M2–N4) + (M1–N2,3)] transitions and the total X-ray production cross-section are determined and compared to other available experimental values and also to those obtained from predictions of the PWBA and the ECPSSR models. The intensity ratios of the transitions are compared with the values calculated from the ECPSSR model. All existing experimental to theoretical ratios of the cross-sections as plotted as a function of the reduced velocity show a universal behaviour