Figure 15.2 — Jablonsky diagram and photoluminescence spectrum Figure 15.2 — Jablonsky diagram and photoluminescence spectrum. (a) Jablonsky diagram of the electronic (bold solid lines) and vibrational/rotational (thin horizontal lines) energy levels of a molecule. The allowed transitions are indicated with arrows: thick solid vertical lines for radiative, i.e., dipole-allowed, transitions; thin solid vertical lines for vibrational or rotational transitions within the same electronic state; and squiggly lines for non-radiative transitions. (b) Photoluminescence spectrum of a single-walled nanotube bundle confined by spectroscopic optical tweezers. Nanotube families in the bundle emit at different wavelengths according to their chiral numbers (shown in brackets).Adapted from Maragò et al., Nature Nanotech. 8, 807–19 (2013).