FIG. 3.

(a) Simulated RP and NRP “homogeneous” 2D fluorescence spectra (real part) of the +2 (iCy3)₂ dimer ss–dsDNA construct for various values of the mean twist angle: ${\overline{\varphi }}_{AB}$ = 80.6° (top row), 82.6° (middle), and 84.6° (bottom); mean tilt angle ${\overline{\theta }}_{AB}$ = 5.1°; mean separation ${\overline{R}}_{AB}$ = 2.8 Å; and homogeneous and inhomogeneous linewidth parameters Γ_H = σ_I = 100 cm⁻¹. (b) Cross sections of the relative deviation of the linear least squares error function, $\mathrm{\Delta }{\chi }_{2DFS}^2\left({\sigma }_R,{\sigma }_{\theta },{\sigma }_{\varphi }\right)/{\chi }_{2DFS,0}^2=\left[\mathrm{\Delta }{\chi }_{RP}^2\left({\sigma }_R,{\sigma }_{\theta },{\sigma }_{\varphi }\right)+\left.\mathrm{\Delta }{\chi }_{NRP}^2\left({\sigma }_R,{\sigma }_{\theta },{\sigma }_{\varphi }\right)\right]\right./2{\chi }_{2DFS,0}^2$, are shown as functions of the standard deviations σ_ϕ (top), σ_θ (middle), and σ_R (bottom). Inhomogeneously broadened spectra of the +2 (iCy3)₂ dimer ss–dsDNA construct were simulated by numerically sampling the library of “homogeneous” 2D fluorescence spectra according to the Gaussian distribution of structural coordinates given in Eq. (21). Error function cross sections are shown plotted relative to their “optimized” values, ${\chi }_{2DFS,0}^2$ (indicated by vertical arrows), which are defined as the 0.5% threshold for cases in which the function approached its minimum asymptotically (as do the σ_ϕ and σ_θ cross sections) and the 0.1% threshold for cases in which the function exhibited a distinct minimum (as shown for the σ_R cross section).