X ray spectroscopy with variable line spacing based on reflection zone plate optics

X ray spectroscopy is a method, ideally suited for investigating the electronic structure of matter, which has been enabled by the rapid developments in light sources and instruments. The x ray fluorescence lines of life relevant elements such as carbon, nitrogen, and oxygen are located in the soft x ray regime and call for suitable spectrometer devices. In this Letter, we present a high resolution spectrum of liquid water, recorded with a soft x ray spectrometer based on a reflection zone plate RZP design. The RZP based spectrometer with meridional variation of line space density from 2953 to 3757 l mm offers extremely high detection efficiency and, at the same time, medium energy resolution. We can reproduce the well known splitting of liquid water in the lone pair regime with 10 s acquisition tim