A hole-burning study of the zero-field splitting of the triplet ground andexcited states of 2,2-dinaphthylcarbene in n-heptane and n-hexane at 1.7 K

Spectral holes were burned within the inhomogeneous 0,0 fluorescence excita tion lines of the T-0 --> T-1 transition of 2,2-dinaphthylcarbene (2,2-DNC) in n-heptane at 1.7 K. The spectrum of holes, attributed to the Z/cis conf ormer of 2,2-DNC, was interpreted with a model taking into account the zero -field splitting (zfs) of both triplet states contributing to the transitio n, enforced C-2 nu symmetry, and the dominance of internal conversion in th e relaxation of the excited T-1 state. Under enforced high symmetry, the nu mber of possible electronic transitions between different spin sublevels of the ground T-0 and excited T-1 states is reduced and the analysis of spect ral position of holes can only provide the differences between the zfs para meters: D-0 - D-1 = 0.558 +/- 0.001 cm(-1) and E-0 - E-1 = 0.0183 +/- 0.001 cm(-1).