Evaluation of LiF lenses as monochromators for inverse photoemission spectroscopy

A LiF lens followed by a pinhole can function as an efficient vacuum ultraviolet monochromator. The principles of such an instrument are described, and its limitations are determined using ray‐tracing calculations. Two practical instruments for ultraviolet inverse photoemission with tunability in the 8–11.7‐eV range are proposed: a biconvex singlet with good resolution (0.23 eV at 10.2 eV) but moderate collection angle ( f/5); and a planoconvex doublet with large collection angle ( f/1.5) but moderate resolution (0.38 eV at 10.2 eV). The main principles have been demonstrated using a prototype instrument.