Fluorescence Spectra of Phenanthridine Isolated in the Supersonic Jet Expansion - An Ab Initio Analysis

I. Deperasińskaa, J. Prochorowa and Y. Stepanenkob aInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland bInstitute of Physical Chemistry and The Laser Center, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland

Full Text PDF

Received: 29 07 2005;

Following the analysis of laser induced fluorescence spectrum of 7,8-benzoquinoline molecule, observed under conditions of isolation in the supersonic jet expansion, the ab initio analysis of laser induced fluorescence spectrum of phenanthridine, observed under the same experimental conditions, was performed. This analysis included: optimization of equilibrium geometry of phenanthridine in its first excited S1 singlet state and computations of the frequencies of vibrational fundamental modes together with their geometry changes between the excited and the ground state. Comparison of the results of calculations with experimental data revealed their good agreement and an increase in the vibrational activity in the fluorescence spectrum in comparison to fluorescence spectrum of phenanthrene molecule (which is a parent aromatic hydrocarbon of phenanthridine and of 7,8-benzoquinoline). Such an increase in vibrational activity in the fluorescence spectrum was earlier observed also for 7,8-benzoquinoline molecule. Present analysis shows that this effect is due to molecular symmetry reduction caused by the substitution of nitrogen atom into the aromatic rings system of phenanthrene, as well as to the changes of equilibrium structure between the ground and excited states.

DOI: 10.12693/APhysPolA.108.1005 PACS numbers: 82.20.Wt, 31.15.Ar, 33.20.Tp