Active cancellation - A means to zero dead-time pulse EPR.
The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power.
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106.
John M
JM
Franck
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106.
Ryan P
RP
Barnes
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106.
Timothy J
TJ
Keller
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106.
Thomas
T
Kaufmann
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106.
Songi
S
Han
D000465:Algorithms; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005583:Fourier Analysis; D008872:Microwaves; D011137:Polystyrenes / Q000737:chemistry; D013696:Temperature
D011137:Polystyrenes
AWG EPR; Active cancellation; Arbitrary Waveform Generation; Dead-time limited EPR; FPGA EPR; Pulse EPR