Figure shows the comparison of the 0-1 and 1-2 CLS decays for the 2021 data set. The two transitions have different initial CLS values (0.3 for the 0-1 and 0.4 for the 1-2) and the CLS decay of the 1-2 transition appears to be marginally faster than the 0-1 peak. We therefore model spectral diffusion of the 0-1 transition as ⟨δω 01 (t)δω 01 (0)⟩ = δ(t)/T hom + Δ 2 exp (-t/τ) and the 1-2 transition as ⟨δω 12 (t)δω 12 (0)⟩ = δ(t)/T hom + β 2 Δ 2 exp (-t/τ) where β is a unitless scaling factor that accounts for the larger 1-2 CLS amplitude seen in Figure (B). We also account for the effect that the shorter 1-2 vibrational lifetime has on the 1-2 dephasing during the second coherence time. Figure shows plots of (A) the cost function and (B) |∇C| � for model fitting to the 2020 data. A first attempt to model the data with a two-Kubo lineshape (blue) does not converge and clearly A second attempt to model the data using a one-Kubo model (orange) immediately converges, implying the data are best modeled by a one-Kubo lineshape. Table shows results for all ten fitting variables. Our earlier analysis of the 2020 data reported a vibrational lifetime of 75 ± 4 ps, which agrees with T LT -1 reported by model fitting in Table (inverting to 72.5 ± 0.3 ps). On the other hand, our earlier report of 5.8 ± 0.3 ps for the CLS time constant is 60% larger than the Kubo time constant reported by model fitting of the same data, 3.57 ± 0.04 ps. Importantly, however, the model fitting value of the 2020 data agrees well with the CLS time constant of 3.3 ± 0.3 ps for the 2021 data and the model fitting Kubo time constant of 3.28 ± 0.02 ps for the 2021 data.