The vibrational structure of the excited electronic state of 1,6-methanolannulene (MA) was measured to confirm the assumption of the delocalized structure of the ground state. If the ground state of MA had an energetic double min., then the electronic excitation would necessitate significant electronic structural changes. A quant. anal. of the band shapes yields rotational consts. for S0 and S1 states.. The very good agreement with the rotational consts. for the ab initio calcd. electronic structure of S0 is a further indication of a delocalized structure. If MA had alternating bonds in the ground state, a progression in the Kekule mode with b1 symmetry must appear. Progressions in only two modes, at wavenumbers 318 and 655 cm-1, were obsd. The rotational structure of these lines shows that both modes are totally sym. Hence, the changes in geometry upon electronic excitation can largely be described with these two coordinates, whereby the mol. symmetry remains unchanged
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