CC BY 4.0 UnportedKleine, CarloEkimova, MariaWinghart, Marc-OliverEckert, SebastianReichel, OliverLöchel, HeikeProbst, JürgenBraig, ChristophSeifert, ChristianErko, AlexeiSokolov, AndreyVrakking, Marc J. J.Nibbering, Erik T. J.Rouzée, Arnaud2022-04-202022-04-202021https://oa.tib.eu/renate/handle/123456789/8748https://doi.org/10.34657/7786We present a novel soft x-ray spectrometer for ultrafast absorption spectroscopy utilizing table-top femtosecond high-order harmonic sources. Where most commercially available spectrometers rely on spherical variable line space gratings with a typical efficiency on the order of 3% in the first diffractive order, this spectrometer, based on a Hettrick-Underwood design, includes a reflective zone plate as a dispersive element. An improved efficiency of 12% at the N K-edge is achieved, accompanied by a resolving power of 890. The high performance of the soft x-ray spectrometer is further demonstrated by comparing nitrogen K-edge absorption spectra from calcium nitrate in aqueous solution obtained with our high-order harmonic source to previous measurements performed at the electron storage ring facility BESSY II.enghttps://creativecommons.org/licenses/by/4.0/530500Absorption spectroscopyCalcium compoundsEfficiencyHarmonic analysisStorage ringsX ray spectrometersDispersive elementsElectron storage ringHigh order harmonicsNitrogen K-edgeReflective zonesSoft-x-ray spectrometersTransient absorption spectroscopiesVariable line-space gratingsX raysArticle