Schematic drawing of free-base porphyrin (H2P). The molecule is in the plane and the axis passes through the opposite hydrogenated atoms.
Fluorescence (left panels) and absorption (right panels) computed spectra of H2P including only the FC contribution or both FC and HT contributions (FCHT). For FC spectra the intensity is affected by the choice of the reference geometry, as shown by comparison of the left and right vertical axes. The intensities on the vertical axes are reported in a.u. (see text) and stands for . The spectra, computed at , have been convoluted with a Gaussian with a . Stick spectra are also reported and the main bands have been assigned as , where is the excited normal mode and its quantum number. Combination bands are reported in parentheses.
Squares of the transition dipole moments of the FC and FCHT absorption and emission spectra, within a range of from the 0-0 transition frequency (set to zero), and normalized so that the 0-0 stick band (the same in absorption and emission) has height of 1.
Upper panel: comparison of the absorption spectrum of H2P obtained by an exact calculation and by only considering equilibrium position displacements (DO). The spectra have been convoluted with a Gaussian with a . In the middle and lower panels both the spectra have been shifted so that their 0-0 transitions are in the origin of the energy axis.
Comparison of the experimental quasiline intensities taken from Ref. 57 with the computed stick bands obtained after changing the zero-order transition dipole moment according to the data reported in Table II (middle panel). Notice that the frequency axis in the computed spectra is shrunk by a factor of 0.95 for a better comparison to experiment. As in Fig. 3, the intensity dependence on the frequency is removed from both the experimental and computed data to better investigate the absorption/fluorescence mirror symmetry.
Upper panel: comparison of the absorption spectrum (convoluted with a Gaussian with a ) of H2P computed at and at ; for the latter case also the stick spectrum is reported. In the middle and lower panels the spectra are compared in a narrower frequency window.
Relevant normal modes of the two electronic states.
Interferences for -polarized transitions and . For brevity only the notation for absorption bands is used. This creates no ambiguity since and modes coincide with the 7 and 13 ones, respectively.
Details of the computation of the absorption spectrum at room temperature.
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