Pulsed-Electron Paramagnetic Resonance Spectrometer

pulse EPR

Pulsed-EPR experiments, including electron spin echo-detected EPR (ESE-EPR), electron spin echo envelope modulation (ESEEM), electron spin echo electron-nuclear double resonance (ESE-ENDOR), Fourier-transform EPR (FT-EPR), and inversion and saturation recovery, are performed on a home designed and constructed pulsed-EPR spectrometer. A guiding principle in the design of the spectrometer was flexibility, both in terms of hardware and software. These features allow the immediate implementation of current developments in the rapidly progressing field of pulsed-EPR spectroscopy, and allow us to tailor the experiments as necessary for different biological samples.

The pulsed-EPR spectrometer operates continuously over X-band (8.2-12.4 GHz) and Ku-band (12.4-18.0 GHz) microwave frequencies. Broadband folded half wave resonators and loop gap resonators, and a modified Varian X-band cavity (TE) resonator are used to achieve different microwave frequencies and optimize different experiments. The detection bandwidth is ≤500 MHz and the pulse timing resolution is ≥1.6 ns. Sample temperatures from <2 K to 295 K are maintained by a Janis cryostat. ESE experiments are typically performed at 6 K. All operations are controlled via GPIB/IEEE-488 PC-device interfaces by using Matlab software.