The rotationally resolved electronic Stark spectrum of 4-cyanoindole and some N-D and C-D deuterated isotopologues has been measured and analyzed.

The rotationally resolved electronic spectrum of 2-cyanoindole has been measured and analyzed using evolutionary strategies. Dipole moments, transition dipole, and life time of the isolated molecule have been extracted and compared to ab initio calculations.

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We determined the electronic nature, the dipole moments and the torsional barriers in the ground and electronically lowest excited singlet state of substituted indoles using rotationally resolved laser induced fluorescence Stark spectroscopy. The electronic origin bands of 1-, 3-and 5-methylindole have been investigated before via high resolution spectroscopy and the perturbation by the hindered internal rotation of the methyl group was discussed in detail by the groups of Pratt and Meerts [1,2]. In general each spectrum consists of two overlapping subbands due to the 0a 1 ← 0a 1 and 1e ← 1e torsional transitions. In 6-methylindole the difference of the torsional level splitting between the 0a 1 and 1e levels in the ground and excited state is large enough, to have the two origins of the subbands shifted more than 90 GHz, i.e. completely separated. Both resulting spectra were evaluated via evolutionary algorithms and compared to the results of ab initio calculations. The rotational constants, the orientation of the transition dipole moment, the size and orientation of the permanent dipole moment, the torsional barrier heights and the orientation of the internal rotor axis in the ground and electronically excited states along with the fluorescence lifetime could be determined. Finally a comparison with the torsional barriers of other methylindoles is given in this presentation.