Atomic hydrogen as high-precision field standard for high-field EPR

Area of Science:

• Physical Chemistry
• Spectroscopy
• Materials Science

Background:

• Electron Paramagnetic Resonance (EPR) spectroscopy requires precise magnetic field calibration.
• Existing standards may have limitations in certain applications or spectral regions.

Purpose of the Study:

• To introduce a novel molecular standard for high-precision magnetic field measurements in high-field EPR.
• To characterize the EPR spectrum and properties of atomic hydrogen trapped in an octaisobutylsilsesquioxane nanocage (H@iBuT₈).

Main Methods:

• Synthesis and characterization of H@iBuT₈.
• Solid-state EPR spectroscopy at variable temperatures.
• Analysis of spectral parameters including g factor and hyperfine coupling constants.

Main Results:

• H@iBuT₈ exhibits a stable EPR spectrum with two narrow lines around g=2.
• The isotropic g factor is 2.00294(3) and temperature-independent.
• The ¹H hyperfine coupling constant is ~1415 MHz, showing slight temperature dependence.

Conclusions:

• H@iBuT₈ serves as a reliable, high-precision magnetic field standard for EPR.
• Its non-overlapping spectrum and ease of preparation make it suitable for organic radicals and other systems.
• The standard is stable at room temperature, enhancing its practical utility.