THE GAS-PHASE PHOTOEMISSION BEAMLINE AT ELETTRA

This paper reports the present stage of commissioning of the gasphase photoemission beamline at Elettra, Trieste. The beamline is designed f or atomic and molecular science experiments with high resolution and h igh-flux synchrotron radiation. It consists of an undulator source, va riable-angle spherical-grating monochromator and two experimental stat ions. The design value of the energy range is 20 to 800 eV with a spec ified resolving power of over 10 000. The procedure adopted for calibr ation of this type of monochromator is discussed. At present a resolvi ng power up to 20 000 and a range up to 900 eV have been measured. Abs orption spectra taken at the argon L-II,L-III-edge and at the nitrogen , oxygen and neon K-edges are as sharp as, or sharper than, any report ed in the literature. The instrumental broadening is well below the na tural line-width making it difficult to quantify the resolution; this problem is discussed.