A Q-band pulsed ENDOR spectrometer for the study of transition metal ion complexes in solids

We describe the design of a pulsed electron nuclear double resonance (ENDOR) spectrometer operating at Q-band frequencies (35 GHz) for studies of transition metal ion complexes in the temperature range between 4.2 and 297 K. Specific features of the spectrometer are a microwave IMPATT generator, a homebuilt cavity, and a commercial Bruker magnet. Standard Davies and Mims ENDOR sequences have been implemented. The performance of the spectrometer is demonstrated for a broad radio frequency range by1H,14N,31P,133Cs, and207Pb pulsed ENDOR experiments of Cu2+, Cr5+, and V4+ transition metal ion complexes in both single crystals and disordered materials.