主题：【求助】XRD衍射仪X光管产生X射线检测样品的深度

在XRD衍射仪中X光管产生的X射线检测样品的深度一般是多少?

The depth for X-ray penetration is only dependent on X-ray wavelength and material composition

Prove:
I = I0 X exp(-ux), where u is linear absorption coeff., x is the sample thickness, I0 is the beam intensitiy, I is the transmission intensity.

figure:
----> I0  IIIIIIIIIIIIIIIIIIII -----> I
                      x

suppose: X-ray passes a material and reduces the amount of transmitted X-ray intensity by half.

1/2 x I0 = I0 x exp ( -u x)
--> ln1 - ln2 = -ux, ln1 = 0, ln2 = 0.693,
therefore,
x = 0.693/u

you can check the u value on some websites which is only depdent on the wavelength, then you can calculate the sample thickness and the intensitiy transmitted.

原文由 xujun16(xujun16) 发表:
在XRD衍射仪中X光管产生的X射线检测样品的深度一般是多少?

The depth for X-ray penetration is only dependent on X-ray wavelength and material composition

Prove:
I = I0 X exp(-ux), where u is linear absorption coeff., x is the sample thickness, I0 is the beam intensitiy, I is the transmission intensity.

figure:
----> I0  IIIIIIIIIIIIIIIIIIII -----> I
                      x

suppose: X-ray passes a material and reduces the amount of transmitted X-ray intensity by half.

1/2 x I0 = I0 x exp ( -u x)
--> ln1 - ln2 = -ux, ln1 = 0, ln2 = 0.693,
therefore,
x = 0.693/u

you can check the u value on some websites which is only depdent on the wavelength, then you can calculate the sample thickness and the intensitiy transmitted.

能否详细的讲解一下关于U的含义，如何确定U的形式，非常感谢您的讲解。

原文由 xujun16(xujun16) 发表:
The depth for X-ray penetration is only dependent on X-ray wavelength and material composition

Well, to be exactly ... it is also depends on packing density of powders. :)

原文由 keshi1990(v3096376) 发表:
能否详细的讲解一下关于U的含义，如何确定U的形式，非常感谢您的讲解。

It should not be "U", it should be "μ".
Please google "linear absorption coefficient"

谢谢iangie兄的补充和纠正。it is also depends on packing density of powders. It should not be "U", it should be "μ".

能否详细的讲解一下关于U的含义，如何确定U的形式。

首先得了解X射线的作用机理，when X-ray interacts with matters, it can cause elastic scattering (diffraction), inelastic scattering (compton scattering) and absorption (it will produce fluorescence background and heat the sample).

When absorption occurs, the μ (linear absorption coefficient) can be considered as the parameter which gives information about how strong a matter can absorb the X-ray. Therefore, the larger the μ, the stronger the matter can absorb the X-ray.

How to use the u, the linear absorption coefficient?

for example, X-ray wavelength is about 1.54 A, u/p (the mass absorption coefficient) = 49.6 cm2/g for aluminum (Al), p is the density of a substance. here, for Al, p is 2.70 g/cm3.
(for these values, you can check the book X-Ray Diffraction Crystallography by Yoshio Waseda  Eiichiro Matsubara Kozo Shinoda, Page 291)

therefore, u (the linear absorption coefficient) = u/p x p = 134 (cm-1)

therefore, x = 0.693/u = 0.693/134 cm = 5.17e-3 cm.

the result is the intensity of X-ray with wavelength 1.54 A will be reduced to half, if the thickness of Al film is 5.17e-3 cm.

如果有错，谢谢大家纠正补充。

本版英语要求好高啊！