Integration of a versatile bridge concept in a 34 GHz pulsed/CW EPR spectrometer

Abstract

We present a 34 GHz continuous wave (CW)/pulsed electron paramagnetic resonance (EPR) spectrometer capable of pulse-shaping that is based on a versatile microwave bridge design. The bridge radio frequency (RF)-in/RF-out design (500 MHz to 1 GHz input/output passband, 500 MHz instantaneous input/output bandwidth) creates a flexible platform with which to compare a variety of excitation and detection methods utilizing commercially available equipment external to the bridge. We use three sources of RF input to implement typical functions associated with CW and pulse EPR spectroscopic measurements. The bridge output is processed via high speed digitizer and an in-phase/quadrature (I/Q) demodulator for pulsed work or sent to a wideband, high dynamic range log detector for CW. Combining this bridge with additional commercial hardware and new acquisition and control electronics, we have designed and constructed an adaptable EPR spectrometer that builds upon previous work in the literature and is functionally comparable to other available systems.

Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids

“…Here, the bandwidth of detection for CW spectra was defined as (0.5*conversion time). The NIST-built 35-GHz spectrometer operates without a reference arm (56). The resonant frequency of the 35-GHz microresonator-microstrip device was first identified on the VNA and then confirmed in the spectrometer.…”

Electron Paramagnetic Resonance Characterization of Sodium- and Carbonate-Containing Hydroxyapatite Cement

“…Continuous wave (CW) EPR spectra were collected of irradiated CHA samples using both a commercial EPR spectrometer operating a 9 GHz (X-band) and a NIST-built EPR spectrometer operating at 34 GHz (Q-band) . X-band EPR spectra were collected with a microwave power of 0.95 mW, modulation amplitude of 0.1 mT, modulation frequency of 100 kHz, 1024 points, conversion time of 29 ms, and 16 scans.…”

“…Continuous wave (CW) EPR spectra were collected of irradiated CHA samples using both a commercial EPR spectrometer operating a 9 GHz (X-band) and a NIST-built EPR spectrometer operating at 34 GHz (Q-band). 96 Xband EPR spectra were collected with a microwave power of 0.95 mW, modulation amplitude of 0.1 mT, modulation frequency of 100 kHz, 1024 points, conversion time of 29 ms, and 16 scans. The incident microwave power was determined to be in the nonsaturating, linear regime based on plots of the integrated intensity of the EPR signal vs the square root of the microwave power.…”