The high resolution Gas Phase Photoemission beamline, Elettra

The Gas Phase Photoemission beamline at Elettra has been commissioned with outstanding success. All photoabsorption spectra taken between 90 and 900 e V have shown resolution which is equal to or higher than any published spec tra. The monochromator is a variable angle spherical grating instrument (pl ane mirror and grating between entrance and exit slits), with an undulator as the source. Some of the problems encountered in commissioning and their solutions are discussed. In particular the calibration is complicated by th e fact that an infinite number of angle pairs of the mirror and grating exi st for a particular photon energy, whereas only one angle pair gives the hi ghest resolution. A second problem is that the resolution is so high that a bove about 80 eV, it is much smaller than the lifetime broadening of any kn own absorption resonance, making any determination of resolution difficult. The experimental chambers available for users are described together with some examples of spectra which have been taken. (C) 1999 Elsevier Science B .V. All rights reserved.