Spectrometer for momentum-resolved bremsstrahlung spectroscopy

A spectrometer for momentum-resolved and polarization-dependent bremsstrahlung spectroscopy (inverse photoemission) in the vacuum UV range is described and the performance of the apparatus is discussed. A Seya-Namioka monochromator combined with a position-sensitive channel plate device for parallel detection of a wavelength range of 165 Å is used as a photon detector and covers an energy regime from 10 to 40 eV with a resolution of 5 Å. Due to the polarization-dependent reflectivity of the gold-coated gratings, the monchromator is also inherently an analyzer for the polarization of the detected light. A space-charge-limited Pierce-type electron gun comprising a BaO dispenser cathode is used as an electron source with 0.1-Å-1 momentum resolution. The overall energy resolution of the apparatus is 0.3 eV at 20 eV photon energy. The sensitivity is 1.8X104 counts per Coulomb and eV for the unoccupied s, p bands of a polycrystalline gold sample.