MICROSCOPIC ULTRAVIOLET PHOTOELECTRON SPECTROSCOPY USING He-I AND He-II RESONANCE LINES

Abstract

A microscopic ultraviolet photoelectron spectrometer (micro-UPS) is developed using a Schwarzschild objective coated with the two-color multilayer which reflects efficiently both He-I (21.2 eV) and He-II (40.8 eV) resonance lines. The spot size by the use of a pinhole of 300 μm diameter is 5 μm, which was measured using the visible light from a Xe lamp. In the present micro-UPS, a pinhole of 2 mm diameter is used to gain sufficient photon intensity, so that the spot size is 25 μm. The valence band spectra of a NiWO 4 microcrystal, which cannot be grown in sufficient size, were measured by the present micro-UPS. The origin of atomic orbitals constituting the valence band of NiWO 4 was elucidated.