Pulsed electron paramagnetic resonance spectroscopy powered by a free-electron laser.

Area of Science:

• Spectroscopy
• Quantum Information Science
• Structural Biology

Background:

• Electron Paramagnetic Resonance (EPR) spectroscopy is vital for studying unpaired electron spins.
• High magnetic fields and coherent pulses enhance EPR power, but high-frequency pulse generation has been a limitation.
• Previous high-power pulsed EPR was restricted to magnetic fields of 3.5 teslas and below.

Purpose of the Study:

• To demonstrate a novel high-power pulsed EPR spectrometer operating at significantly higher frequencies and magnetic fields.
• To overcome the limitations of existing solid-state sources for pulsed EPR.
• To enhance the capabilities of EPR for probing complex systems and quantum phenomena.

Main Methods:

• Utilized a one-kilowatt free-electron laser to power a pulsed EPR spectrometer at 240 gigahertz (8.5 teslas).
• Developed advanced quasi-optical technology for efficient high-frequency pulse delivery.
• Employed Fourier-transform EPR techniques for spectral analysis.

Main Results:

• Achieved a transformative enhancement in pulsed EPR capabilities compared to state-of-the-art solid-state sources.
• Demonstrated significantly faster electron spin rotation (6 ns vs. 300 ns).
• Successfully measured short decoherence times (63 ns) in nitroxide free-radicals at 190 K and resolved EPR lines separated by 200 MHz in diamond.

Conclusions:

• The developed free-electron laser-based pulsed EPR spectrometer pushes the boundaries of high-field EPR spectroscopy.
• The technology is scalable to terahertz frequencies, opening new avenues for research in condensed matter physics, quantum computing, and structural biology.
• This advancement provides unprecedented resolution and speed for studying electron spin dynamics.