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![[Figure 1]](xx5044fig1mag.jpg)
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Figure 1
Schematics of (a) the geometry of an X-ray scattering experiment from a liquid surface (blue part) and (b) the resolution boxes in Qxy space that correspond to square areas on the detector in which the scattered photons are integrated (summed over), named as `area of integration'. (a) The sketch depicts the wavevectors ki and kf of the incident and the scattered beam, respectively, with a detector positioned at the angle (β, 2θ) to measure the intensity of the scattered beam. Plane yz is the plane of incidence. (b) The black resolution box represents the region of the intergral in Qxy space corresponding to a typical specular reflectometry measurement. It relates to the angular range of the integral in equation (4) ![[link]](../../../../../../logos/arrows/j_arr.gif){kind=small} used to calculate R. The red box represents the typical integral region for a GIXOS measurement and it relates to the integral angular range in equation (6) used to calculate
R*. [The example resolution boxes in (b) are calculated using a similar instrument setting to those used in our measurements: an incident energy of 15 keV, Δβ = Δ2θ = 0.08° set by an area of integration of 0.85 × 0.85 mm at 0.6 m from the sample. Both boxes are calculated for Qz = 0.4 Å−1: for the specular resolution (black) α = β = 1.5°, and for GIXOS resolution (red), α = 0.07°, β = 2.94°. 2θ for GIXOS is set to 0.0754°.] The Qxy center of the box is defined by (β, 2θ) of the center of the area of integration [see the calculation of (Qx, Qy)]: the box for the area of integration around a specular position (α = β, 2θ = 0) is centered at the origin of the Qxy space (black), while the center of the box around an off-specular position (α ≠ β, 2θ ≠ 0) is displaced from the origin (red). |
![[Figure 1]](xx5044fig1.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
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