Dear Mulatu,

you only get the same Au signal (for example the relative step height) of the L2 and/or the L3 edge when the Au mass coverage of both of your samples (Au-foil and Au-NPs) is equal. This might be not the case for your Au foil and the Au-NP sample.

The thickness of your Au-foil might be too thick.

How do you have managed to have the same mass coverages?

Just to compare the intensities makes no sense because a) in case of your NPs you have got additional Cu content which decreases X-ray photon flux and b) your mean mass density of your NP sample does propably not represent any bulk density value. Lambert Beer attenuation law is applicable, but you don't really know the thickness or the density or the mass coverage especially for your Au-NP sample.

Please explain a bit in more detail your measurement set up and what kind of measurements you have done,

....and what is the aim of your spectral x-ray transmission measurements?

Thanks in advance.

Remark: for example, when intending to measure the ratio of the Au to Cu mass, you need to do two spectral transmission experiments:

a) measurement of the relative step height of the Au L2- and /or the L3-edge will give you the Au mass coverage [ e.g in g/cm²], and

b) measurement of the relative step height of the Cu K-edge will give your the mass coverage of Cu;

the ratio of these two mass coverages will give the mass ratio.

Gerhard Martens: Thank you so much!