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Science Forum Index » Physics - Research Forum » Experimental determination totalreflection (X-Ray)
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Message |
| Oliver Werzer |
 Posted: Sun Mar 13, 2005 9:10 pm |
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Guest
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Hello
I do x-ray reflectivity measurements on organic films.
To measure the the curve is not a big deal, but to
determine the total external reflection is difficult.
For a smooth surface and high scattering from the material
the edge is very 'sharp'. But this is not the case for my
materials. Therfore it is hard to find the exact value
of the total external reflection. Is there a exact mathematical
way to find the angle?
best regard
oliver |
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| Guest |
| Posted: Tue Mar 15, 2005 8:22 am |
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Get onto the LBL site for calculating x-ray refelctivity. You will
need to know the chemical formula for your film and its density. The
program will give you reflectivity as a function of energy at a fixed
angle or reflectivity as a function of angle for fixed energy.
The loss due to roughness is often approximated by the Debye Waller
factor R=R0exp(-(4*pi*sigma*sin (theta)/Lambda^2)^2
where sigma is the rms roughness in angstroms, Ro is reflectivity for
zero roughness, theta is the grazing angle, and lambda is the
wavelength in angstroms.
Oliver Werzer wrote:
Quote: Hello
I do x-ray reflectivity measurements on organic films.
To measure the the curve is not a big deal, but to
determine the total external reflection is difficult.
For a smooth surface and high scattering from the material
the edge is very 'sharp'. But this is not the case for my
materials. Therfore it is hard to find the exact value
of the total external reflection. Is there a exact mathematical
way to find the angle?
best regard
oliver |
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| Werzer Oliver |
| Posted: Fri Mar 18, 2005 8:39 am |
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Guest
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That's a problem.
Sometimes I do not have informations
on all components of the film. And also
if you do temperature dependent experiments
the parameters are not known, since the change
during the experiment. Therefore I
look for a method to find the angle of total
reflection experimentally. Then I can calculate
the other parameters.
(e.g. cos(theta)=sqrt(2*delta),...)
The only thing I found
is to look for the half of the intensity and mark this
as the angle of totalreflection. But this is in my opinion
not enough.
best regars
oliver
dbohara@mindspring.com wrote:
Quote: Get onto the LBL site for calculating x-ray refelctivity. You will
need to know the chemical formula for your film and its density. The
program will give you reflectivity as a function of energy at a fixed
angle or reflectivity as a function of angle for fixed energy.
The loss due to roughness is often approximated by the Debye Waller
factor R=R0exp(-(4*pi*sigma*sin (theta)/Lambda^2)^2
where sigma is the rms roughness in angstroms, Ro is reflectivity for
zero roughness, theta is the grazing angle, and lambda is the
wavelength in angstroms.
Oliver Werzer wrote:
Hello
I do x-ray reflectivity measurements on organic films.
To measure the the curve is not a big deal, but to
determine the total external reflection is difficult.
For a smooth surface and high scattering from the material
the edge is very 'sharp'. But this is not the case for my
materials. Therfore it is hard to find the exact value
of the total external reflection. Is there a exact mathematical
way to find the angle?
best regard
oliver
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