[x-ray physics] refractive index

[DivGradCurl]

There doesn't seem to be any difference between

$$n = (1-\delta) - i\beta$$
(the refractive index in the x-ray regime, where $$1-\delta$$ is the real part and $$\beta$$ is the the absorption index)

and

$$n^{\ast} = n - ik$$
(the complex refractive index, where $$n$$ is the refractive index and $$k$$ is the extinction coefficient)

assuming the equivalence $$n = 1-\delta$$ and $$k=\beta$$. I got this from http://henke.lbl.gov/optical_constants/getdb2.html, where I looked up the refractive index of a material. Is there any physical meaning associated with this different notation or it's just a matter of preference? Thanks!

 

[Evalesco]

It looks like the two equations you mentioned are mathematically equivalent, however there is some physical meaning to the different notation. The equation n = (1-\delta) - i\beta represents the refractive index in the x-ray regime, which is a measure of how light propagates through a medium (the real part 1-\delta reflects the speed of light and the imaginary part \beta reflects the absorption of light). On the other hand, the equation n^{\ast} = n - ik represents the complex refractive index, which takes into account both the speed of light and the extinction coefficient, which measures how much light is absorbed by the medium.

 

[astrokreng]

The notation used for the complex refractive index in x-ray physics is a matter of convention and preference, and both notations are commonly used in literature. However, there is a physical meaning associated with the different components of the complex refractive index.

The real part, 1-\delta, represents the refractive index of the material, which describes how much the material slows down the speed of light as it passes through it. This is related to the material's density and atomic properties.

The imaginary part, \beta or k, represents the absorption index or extinction coefficient, which describes how much the material absorbs the x-rays as they pass through it. This is related to the material's electronic and atomic structure.

So while the two notations may seem equivalent, they actually provide different information about the material's properties. It is important to use the correct notation when interpreting and analyzing experimental data.