Measuring distances between unpaired electron spins is an important application of electron paramagnetic resonance. The longest distance that is accessible is limited by the phase memory time of the electron spins. Here we show that strong continuous microwave irradiation can significantly slow down relaxation. Additionally, we introduce a phase-modulation scheme that allows measurement of the distance during the irradiation. Our approach could thus significantly extend the accessible distances.

This paper analyzes a commonly used line-narrowing mechanism (homonuclear decoupling) in solid-state NMR and discusses what limits the achievable line width. Based on theoretical considerations, the contribution of different effects to the line width is discussed and a new contributing term is identified. This research allows us to evaluate new ways to improve the line width in such homonuclear decoupled spectra.