Fig. 3.

Diagram of the potential energy surfaces. Left: diagram of the potential energy surfaces for the G, D⁺A⁻ and LE intrinsic (diabatic) states when $\mathrm{\Delta }{E}_{\mathrm{LE}-{\mathrm{D}}^{+}{\mathrm{A}}^{-}}=1.1\mathrm{eV}\left(8871{\mathrm{cm}}^{-1}\right)$; right: diagram of the potential energy surfaces for the adiabatic states when $\mathrm{\Delta }{E}_{\mathrm{LE}-{\mathrm{D}}^{+}{\mathrm{A}}^{-}}=1.1\mathrm{eV}\left(8871{\mathrm{cm}}^{-1}\right)$, $t_{{\mathrm{D}}^{+}{\mathrm{A}}^{-}-\mathrm{G}}=30{\mathrm{cm}}^{-1}$, and $t_{{\mathrm{D}}^{+}{\mathrm{A}}^{-}-\mathrm{LE}}=300{\mathrm{cm}}^{-1}$. Here, $E_{\max }^{\mathrm{CT}}$ is the energy of the maximum CT absorption derived in the semi-classical two-state model; the region circled by the yellow dashed line represents the ‘hot’ CT vibronic states