This paper reports the present stage of commissioning of the gas-phase photoemission beamline at Elettra, Trieste. The beamline is designed for atomic and molecular science experiments with high-resolution and high-flux synchrotron radiation. It consists of an undulator source, variable-angle spherical-grating monochromator and two experimental stations. The design value of the energy range is 20 to 800 eV with a specified resolving power of over 10000. The procedure adopted for calibration of this type of monochromator is discussed. At present a resolving power up to 20000 and a range up to 900 eV have been measured. Absorption spectra taken at the argon L(II,III)-edge and at the nitrogen, oxygen and neon K-edges are as sharp as, or sharper than, any reported in the literature. The instrumental broadening is well below the natural line-width making it difficult to quantify the resolution; this problem is discussed.

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X-ray absorption spectra of gas-phase VOCl(3) and CrO(2)Cl(2) have been measured in the metal L(2,3)-edge and O K-edge regions. The assignment of the spectral features is based on the relativistic two-component ZORA TDDFT approach. The calculations provide results in excellent agreement with the experimental spectra and prove the importance of including both configuration mixing and spin-orbit coupling in the theoretical description to obtain a reliable simulation of the transition metal L(2,3)-edge. The calculations are extended also to the MnO(3)Cl molecule to discuss the spectral variations along the series of the oxychlorides both in the metal L(2,3) and ligand O K spectra.

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