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SynopsisThe electronic structure of water and methanol as vapours, liquids, as well as liquid mixture is determined using synchrotron-based X-ray photoemission spectroscopy on liquid μ-jets.These results together with density functional theory provide, among others, interesting insight into the hydration of these two molecules in the liquid phase mixture.Abstract The advent of liquid μ-jet setups as proposed by Faubel and Winter -in conjunction with X-ray Photoemission Spectroscopy (XPS) -has opened up a large variety of experimental possibilities in the field of atomic and molecular physics. In this study, we present first results from a synchrotron-based XPS core level and valence band electron spectroscopy study on water (10 -4 M aqueous NaCl solution) as well as a water/methanol mixture using the newly commissioned ALBA liquid μ-jet setup. The experimental results are compared with simulations from density functional theory (DFT) regarding the electronic structure of single molecules, pure molecular clusters, and mixed clusters configurations as well as previous experimental studies. We give a detailed interpretation of the core level and valence band spectra for the vapour and liquid phases of both sample systems. The resulting overall picture gives insight into the water/methanol concentrations of the vapour and liquid phases as well as into the local electronic structure of the pertinent molecular clusters under consideration, with a special emphasis on methanol as the simplest amphiphilic molecule capable of creating hydrogen bonds.

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The performance of microfocus beamlines, and ultimately the quality of the diffraction data, is very sensitive to vibrations affecting the optical elements and the sample stages and holder. We report here the strategies applied in the design of the microfocus MX XAIRA beamline at ALBA synchrotron to mitigate the effects of two relevant sources of vibrations: circulation of LN2 flow to evacuate the thermal load on the monochromator and cryocooling gas stream being blown on the sample. The internal shape and size of the two cooling pads that clamp the monochromator optics have been designed to minimize the turbulences in the liquid nitrogen flow while maximizing heat transfer. Computational Fluid Dynamics (CFD) simulations and some preliminary metrology tests are presented. Besides, in the end-station, the cryo-cooler is blowing typically a 5-10 L/min flow of nitrogen or helium gas at 100K on the sample, inducing vibrations in the micron range. The optimal geometrical configuration between the sample holder and the cryocooler has been assessed by means of CDF simulations and metrology tests.

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