To characterize the luminescence properties of the CBN ribbons, the equilibrium geometry of the S1 state was determined with the ADC(2) method. The relaxed energy of the S1 state relative to the energy of the electronic ground state provides the spectroscopic 0-0 transition energy E0-0 (neglecting differences of zero-point vibrational energies of the S0 and S1 states). In the Condon approximation, the maximum of the emission spectrum is given by the vertical emission energy Eem, that is, the difference of the energies of the S1 and S0 states at the S1 equilibrium geometry. The oscillator strength for fluorescence likewise is computed at the equilibrium geometry of the S1 state. Table . Vertical excitation energies (Ev), 0-0 excitation energies (E0-0), vertical emission energies (Eem) (in eV) and oscillator strengths of absorption (fabs) and emission (fem) of the S1 and T1 states of the CBN_1-2 and CBN_2-2 ribbons, computed with the ADC( In Table , the spectroscopic data for luminescence are compared with the data for absorption for the examples of CBN_1-2 and CBN_2-2. The corresponding CC2 results can be found in Table . It is remarkable that the E0-0 energies are only slightly lower than the vertical excitation energies for both ribbons. The vibrational stabilization energy of the S1 state is of the order of merely 0.1 eV. Likewise, the vertical emission energies Eem are only marginally lower than the E0-0 energies. The oscillator strengths for absorption and emission are nearly identical. All these features are signatures of the remarkable rigidity of the CBN ribbons upon excitation to the S1 state. The results shown in Table are representative for all CBN_1-m and CBN_2-m ribbons.