Design and performance of an oversized-sample 35 GHz EPR resonator with an elevated Q value

Area of Science:

• Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Continuous-wave electron paramagnetic resonance (EPR) spectroscopy at 35 GHz offers superior g-tensor resolution for complex systems compared to lower frequencies.
• Studying unstable or sensitive paramagnetic centers benefits from using a single sample across multiple EPR frequencies.
• Limited availability of oversized-sample resonators at 35 GHz restricts researchers to lower frequencies or smaller sample sizes, potentially compromising sensitive material analysis.

Purpose of the Study:

• To design and evaluate a novel oversized-sample resonator for 35 GHz continuous-wave and pulsed EPR.
• To achieve high sensitivity, robustness, and ease of use for a wide range of paramagnetic samples.
• To enable reliable EPR measurements at variable temperatures, including cryogenic conditions.

Main Methods:

• The resonator design was guided by electromagnetic field simulations.
• A cylindrical cavity utilizing the TE011 mode was engineered to accommodate 3 mm sample diameters.
• Microwave characteristics of manufactured prototypes were experimentally validated against simulation predictions.

Main Results:

• The oversized-sample resonator achieved a high loaded Q value (QL) of up to 2550.
• Experimental results confirmed the resonator's performance aligned with electromagnetic simulations.
• The resonator demonstrated compatibility with commercial EPR spectrometers and cryogenic systems (down to 1.8 K).

Conclusions:

• The developed 35 GHz oversized-sample resonator provides a robust and sensitive platform for EPR spectroscopy.
• Its design facilitates the study of challenging paramagnetic species, including metal centers and organic radicals with narrow lines.
• This advancement supports multi-frequency EPR studies and enhances the analysis of sensitive materials across a broad temperature range.