Figure 5.

The mono-exponential decay of magnetization due to chemical exchange under free precession conditions is a consequence of the exponential dwell time distributions of the GS and ES. (A and B) Normalized bulk x-magnetization M_GSx (black dots) of the GS as a function of time for a system undergoing GS-ES exchange, simulated using the vector model. An exponential fit to the magnetization is shown in red. Panel A is simulated assuming exponential probability distributions for the GS and ES dwell times (< τ_GS > = 0.33 s and < τ_ES > = 0.14 s), while panel B is simulated assuming that the ES and GS dwell times follow a standard normal distribution. Expressions for the probability distributions of τ_GS and τ_ES are given in the inset. Simulations assumed the following exchange parameters: $\Delta \overline{\omega }{\text{ (}}^{13}\text{C)}=3\text{\hspace{0.17em}ppm}$, γ(¹H)B₀/2π = 700 MHz, and R_1,GS= R_1,ES = R_2,GS = R_2,ES = 0 s⁻¹ for panels A and B.