Inverse photoemission spectrometer using a BaF2 window for a low-pass filter

We have built a simple and high performance inverse photoemission spectrometer using a BaF2 window and a Cu–BeO electron multiplier with KBr as the photocathode for low- and high-pass filters, respectively. It is found that using the BaF2 low-pass filter improves the resolution by 0.2 eV to compare with SrF2. The intensity was reduced to a quarter of that with SrF2, although it is enough to obtain good inverse photoemission spectra.