Reflectivity oscillations below critical angle - Revision history

KevinYager at 19:56, 15 October 2014

2014-10-15T19:56:55Z

KevinYager at 19:56, 15 October 2014

2014-10-15T19:56:35Z

KevinYager: Created page with "In reflectivity experiments, when the angle of incidence is below the critical angle, the beam experiences total external reflection. Image:Reflectivity example..."

2014-10-15T19:52:32Z

Created page with "In reflectivity experiments, when the angle of incidence is below the critical angle, the beam experiences total external reflection. Image:Reflectivity example..."

New page

In [[reflectivity]] experiments, when the angle of incidence is below the [[critical angle]], the beam experiences [[total external reflection]].

[[Image:Reflectivity example-real density.png|thumb|center|400px|Reflectivity calculation in a film with purely-real density (no absorption).]]
[[Image:Reflectivity example-complex density.png|thumb|center|400px|Reflectivity calculation in a film with a complex density (finite value of the imaginary part of the complex potential; corresponds to film absorption).]]

← Older revision		Revision as of 19:56, 15 October 2014
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−	In [[reflectivity]] experiments, when the angle of incidence is below the [[critical angle]], the beam experiences [[total external reflection]]. Thus, the reflectivity goes to 100% (<math>\scriptstyle R =1 </math>) for any <math>\scriptstyle \theta ~~\lt~~ \theta_c</math>, or for <math>\scriptstyle q ~~\lt~~ q_c</math>.	+	In [[reflectivity]] experiments, when the angle of incidence is below the [[critical angle]], the beam experiences [[total external reflection]]. Thus, the reflectivity goes to 100% (<math>\scriptstyle R =1 </math>) for any <math>\scriptstyle \theta < \theta_c</math>, or for <math>\scriptstyle q < q_c</math>.

	However, one sometimes sees oscillations of the reflectivity even below this angle (especially in [[x-ray]] reflectivity, though it is also possible in neutron reflectivity). These oscillations can be thought of as [[waveguide]] modes appearing while the reflectivity angle is in between the critical angle of the substrate, and the critical angle of the film. Notably, these variations are only visible (in reflectivity) due to the non-zero absorption of the film. However, even a very small absorption can be measured, because the waveguide modes inherently travel through the film many times.		However, one sometimes sees oscillations of the reflectivity even below this angle (especially in [[x-ray]] reflectivity, though it is also possible in neutron reflectivity). These oscillations can be thought of as [[waveguide]] modes appearing while the reflectivity angle is in between the critical angle of the substrate, and the critical angle of the film. Notably, these variations are only visible (in reflectivity) due to the non-zero absorption of the film. However, even a very small absorption can be measured, because the waveguide modes inherently travel through the film many times.

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-In [[reflectivity]] experiments, when the angle of incidence is below the [[critical angle]], the beam experiences [[total external reflection]].
+In [[reflectivity]] experiments, when the angle of incidence is below the [[critical angle]], the beam experiences [[total external reflection]]. Thus, the reflectivity goes to 100% (<math>\scriptstyle R =1 </math>) for any <math>\scriptstyle \theta \lt \theta_c</math>, or for <math>\scriptstyle q \lt q_c</math>.
 [[Image:Reflectivity example-real density.png|thumb|center|400px|Reflectivity calculation in a film with purely-real density (no absorption).]]
 [[Image:Reflectivity example-complex density.png|thumb|center|400px|Reflectivity calculation in a film with a complex density (finite value of the imaginary part of the complex potential; corresponds to film absorption).]]