The first experimental evidence is presented for a strong coupling between electronic states in isolated, supercooled 4-(N,N-dimethylamino)benzonitrile, DMABN. In the fluorescence excitation spectrum, measured under isolated supercooled conditions, two types of transitions were found (B-type and C-type). Rotational contour analysis of the B-type bands (ππ* character) shows that there is hardly any difference between the geometries of the ground and excited states; the molecule retains its planar conformation. In the out-of-plane transition (C-type band) the equilibrium position of the dimethylamino group twists 90° with respect to the benzonitrile part. The broadening of the rotational lines indicates that the fluorescence is preceded by a fast radiationless intramolecular process (internal conversion) on a picosecond time scale. For the B-type bands it was found that the broadening increases with the vibrational energy.
|Number of pages||9|
|Journal||Journal of Physical Chemistry A|
|Publication status||Published - 9 Apr 1999|
- supercooled molecules
- energy transitions
- solar energy conversion
- solar energy storage