A Novel 263 GHz pulse EPR Spectrometer for Chemical Spectroscopy

This project focuses on the development of high power, high bandwidth pulse Electron Paramagnetic Resonance (EPR) spectroscopy establishing optimized and novel capabilities for investigating topics of high chemical relevance. Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) are powerful techniques for obtaining information about chemical structures and reaction mechanisms. EPR spectroscopy focuses on unpaired electrons present in various chemical entities and is historically performed at high resonance frequencies, e.g. the microwave frequency range; whilst NMR spectroscopy targets magnetic nuclei employing a lower radio frequency range. NMR spectroscopy has benefited from the use of very high magnetic fields to push the NMR radio frequencies higher to gain increased sensitivity and spectral resolution. However, similar advancements in EPR spectroscopy have only recently been realized as technology for powerful pulse amplifiers at higher frequencies has been lacking. Using the newly developed vacuum tube mm-wave amplifier, this project will achieve higher frequency at matching high magnetic field to maximize the magnetic moment of the unpaired electrons, particularly at low sample temperatures. This will allow studies employing essentially 100% pure quantum spin state populations for cryogenic temperature EPR spectroscopy, which will be a significant innovation for advancing quantum information science based on electron spins. This new route into sensitive and powerful quantum magnetic resonance will allow direct training of STEM workforce in this important field. Specifically, the EPR spectrometer will be enhanced with hardware and software improvements to enable a variety of pulse EPR sequences to facilitate detection of nuclear spin transitions via the pulsed electron spin signals and bring high power mm-wave pulse EPR spectroscopy to bear on topics of high chemical relevance. With lower loss corrugated waveguide and improved thermometry, the instrument will allow accurate temperature measurements at the cold cryogenic temperatures (below 4.2K) providing the purest spin states for quantum information in a variety of tailored compounds. The high frequency of the 263 GHz EPR instrument will provide much higher resolution of high spin d and f block transition metals, allowing increased chemical and quantum information than achieved at conventional EPR frequencies where the intrinsic zero field splitting greatly broadens EPR lineshapes. The use of shaped mm-wave pulses in the new instrument will allow us to do exquisite manipulation of quantum spin states in such complexes, starting with the nearly pure quantum population in the ground spin that the high field and low temperature afford. Addition of an electrochemical interface will facilitate EPR spectroelectrochemistry of catalysts and battery anodes and cathodes. And the development of high field/frequency time domain dynamic nuclear polarization methods to transfer the very high electron spin polarization to nuclei will provide higher sensitivity for solid state NMR spectroscopy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2604076 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Ralph Britt | Institution: University of California-Davis, DAVIS, CA | Award Amount: $861,531 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2604076 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2604076.html