What is it about?
The first publication of the series on single-shot reflectivity acquisition from liquid surfaces using grazing incidence off-specular scattering (GIXOS) geometry. It builds on the pioneering works of Daillant (1992), Wiegart (2005), Dai (2011), etc. This method allows to obtain reflectivity for more than 11 orders of magnitude in a single exposure. This paper presents the simplest case - liquid surface with low surface stiffness - to explain the analytical form to transform between GIXOS data and specular reflectivity. More complicated cases will be described in the fore-coming manuscripts.
Why is it important?
This paper provides a clear analytical form that transforms GISAXS signal into reflectivity curve for liquid surfaces. This form can be used on the data from any liquid surface diffractometer. The obtained reflectivity reaching 10^-12, Qz > 1.2/A enables structural analysis at higher spatial resolution; Working under fixed grazing incidence geometry allows much better surface sensitivity and simpler instrument construction, and reduced beam damage due to the elongated footprint; The single shot measurement manner allows operando, in situ and pump-X-ray-probe measurement scheme.