can be realized in the case of Fig. \[fig\_st\](b). The obtained spectra shown in Fig. \[fig\_sp\] illustrate clear differences according to the interaction topology differences presented in Fig. \[fig\_st\](a, b, c).

![(Color online) Sketch of 2-propanol molecule in acetone-d6 with magnetic impurities (Fe(III) ions). The chain of the $^{13}$C spins is surrounded by the H spins. These H spins can be selectively nullified by decoupling techniques, which provides three different noisy environments. The gray areas corresponds to the System II’s and Markovian Environments. []{data-label="fig_st"}](Pr2_idea){width="8.6cm"}

![ Spectra of the $^{13}$C spins in different decoupling conditions: (a) without decoupling, (b) selective decoupling by applying a small continuous rf whose frequency was the Larmor one of HC, and (c) full decoupling by applying the WALTZ sequence on all H spins. The sample is 0.41 M 2-propanol in acetone-d6 with 12 mM of Fe(III)acac. The peaks at 62.6 ppm are from the center $^{13}$C of the chain, while those at 25.5 ppm from the side $^{13}$C’s. The spectra (a, b) are magnified three times as one can see from the apparently large impurity signals at 30 ppm. []{data-label="fig_sp"}](Pr2_C_sp2){width="8.6cm"}

The Hamiltonian governing the nuclear spin dynamics of 2-propanol is given as $$\begin{aligned}
\label{eq_mol_ham}
 {\mathcal H} 