Fig. 3: ³Chl a optically detected magnetic resonance (ODMR) spectra of rVCP.

a Jablonski diagram of the main electronic states of Chls and Cars in LHCs (in green and orange, respectively). The states are arranged vertically by energy (not in scale), and horizontally by spin multiplicity. Absorption (A), fluorescence (F), and ISC are indicated by straight grey arrows; singlet-singlet (S-S) and triplet-triplet (T-T) energy transfers by curved dashed grey arrows; the transitions between the spin sublevels by double-pointed black arrows. For readability, only the transitions more relevant for the discussion of the results are drawn. The triplet sublevels are highlighted by dashed boxes for the two molecules. The relative populations of the triplet sublevels are indicated by the thickness of the level bars. At the bottom of the panel, the molecular structure of chlorophyll a (Chl a) and lutein (Car) with the directions of the zero-field splitting principal axes (zfs, the axes of the dipolar interaction between the two unpaired electrons) are reported (in blue arrows). b Absorption (black line) and fluorescence emission (red line, excitation wavelength 481 nm) spectra of rVCP²⁴. Temperature 77 K. c FDMR spectra (black lines) of the ³Chl |D|−|E| and |D|+|E| transitions at different wavelengths in the 680–760 nm range, as indicated. Amplitude modulation frequency 33 Hz, time constant 100 ms, temperature 1.8 K. The spectra are vertically shifted for better comparison. Reconstruction (green lines) of the experimental spectra as a sum of Gaussian components (blue and red lines). The fitting parameters are reported in Supplementary Table S2. d T-S spectra of ³Chl a. Resonance frequencies: 733 MHz (black line), 945 MHz (red line), and 1000 MHz (blue line). Amplitude modulation 33 Hz, time constant 1 s, temperature 1.8 K.