We believe that, in addition to nontrivial theoretical interest, the proposed work offers experimenters a reliable time interval in which the experimentally measured signal allows for a relatively simple interpretation uncomplicated by contributions from three-particle dynamical correlations of having spin nuclei in condensed matter.

Electron spins sense their environment via magnetic interactions. An important contribution stems from nuclear spins in their vicinity. They cause loss of coherence and thus reduce resolution of spectra obtained by experiments on electron spins and the efficiency of transferring electron-spin magnetization to other nuclear spins. Here we study how protons in trityl radicals contribute to coherence loss. Such coherence loss is slower in the presence of a strong microwave field.

Sensitivity is often a limiting factor in electron–nuclear double resonance (ENDOR). Here we demonstrate how using chirp radiofrequency pulses can improve ENDOR sensitivity up to 3–9 fold, with the strongest increase for broader lines often encountered in disordered solids for nuclei such as nitrogen and metals. The resulting drastic speedup in acquisition times also renders 2D ENDOR more feasible, as we demonstrate in TRIPLE, showing correlations with Cu hyperfine couplings.

Electron spin dynamics during microwave irradiation are of increasing interest in electron paramagnetic resonance (EPR) spectroscopy. Here, we show that these dynamics can be probed by modern pulsed EPR experiments that use shaped microwave pulses. Combined with spin dynamics simulations, these results provide a starting point for optimizing existing EPR experiments and for developing new pulse sequences.