FAR-INFRARED ELECTRON-PARAMAGNETIC-RESONANCE SPECTROMETER UTILIZING AQUASI-OPTICAL REFLECTION BRIDGE

We describe a far-infrared electron-paramagnetic-resonance (EPR) spect rometer for broadband (100-300 GHz) use. The spectrometer is operated in the reflection mode and uses broadband quasioptical methods to sepa rate the transmitted from the reflected radiation. We describe and ill ustrate its operation at 170 GHz (1.8 mm) and compare its performance to that of our transmission mode spectrometer operating at 250 GHz. We also discuss the advantages of the reflection bridge for performing E PR experiments over a broad range of frequencies, and we consider meth ods of improving the performance of the bridge. This includes a novel design for variable coupling of the reflection-mode Fabry-Perot resona tor. (C) 1996 American Institute of Physics.