A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

We describe a pulsed electron paramagnetic resonance spectrometer operating at several frequencies in the range of 110-336 GHz. The microwave source at all frequencies consists of a multiplier chain starting from a solid state synthesizer in the 12-15 GHz range. A fast p-i-n-switch at the base frequency creates the pulses. At all frequencies a Fabry-Perot resonator is employed and the pi/2 pulse length ranges from approximately 100 ns at 110 GHz to approximately 600 ns at 334 GHz. Measurements of a single crystal containing dilute Mn(2+) impurities at 12 T illustrate the effects of large electron spin polarizations. The capabilities also allow for pulsed electron-nuclear double resonance (ENDOR) experiments as demonstrated by Mims ENDOR of (39)K nuclei in Cr:K(3)NbO(8).