Electronic spectroscopy and methyl internal rotation dynamics of 9,10-dimethylanthracene

Fluorescence excitation, dispersed fluorescence, and double resonance fluorescence depletion spectra of jet-cooled 9,10-dimethylanthracene (DMA) have been measured. The spectra exhibit evidence of strong coupling between methyl group motion and the anthracene frame vibrations. Fluorescence depletion experiments have shown the presence of rovibronically selective intersystem crossing in DMA. The results of DFT calculations together with potential energy surface scan of the ground and lowest excited singlet state are presented.