Figure 2: Detailed analysis of quantum nuclear effects in the diamondoids.
From: Quantum nuclear dynamics in the photophysics of diamondoids
(a) Fine structure in the optical spectrum of adamantane near the absorption onset. The blue line is the experimental spectrum from Landt et al.24, and the black line is the spectrum calculated using equation (2). The coloured vertical dashed lines and corresponding ball-and-stick models with arrows refer to the vibronic progressions discussed in the text. The thick dashed blue lines correspond to the A1 mode with energy 149.4 meV. The vibration patterns shown on the top are colour-matched to the corresponding vertical bars. (b) Comparison between measured and calculated optical gaps of diamondoids. Vertical excitations (yellow arrow/bars) cannot explain the measured band gaps (blue bars), while adiabatic excitations (red arrow/bars) are in very good agreement with experiment. (c) Triplet splitting of the T2 HOMO of adamantane as a function of the T2 C–C stretching mode illustrated by the arrows. (d) ISMC calculation of the density-of-states of adamantane near the HOMO. The energy axis is aligned with the HOMO calculated for nuclei clamped at their equilibrium positions. The red area is obtained by considering only the coupling to the T2 modes, the blue area is obtained by considering all vibrational modes. The thick black line corresponds to the valence band top in diamond obtained in RamÃrez et al.26 using path-integral molecular dynamics.
