Analysis of the Origin Band of Acridine Dimer Fluorescence Excitation Spectrum --- Conformations of Jet-Cooled Acridine Dimer |
| I. Deperasińska and J. Prochorow Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland |
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| Received: August 8, 2001 |
| The analysis of rotational band contour for the origin transition of fluorescence excitation spectrum of acridine dimer, earlier observed under conditions of jet-cooling in supersonic helium expansion, has been performed. An optimized ground-state equilibrium structure of acridine dimer fits the approximation of asymmetric top rigid rotor. In this approximation rotational constants were determined and an A-type rotational band was computed. It has turned out that the computed rotational band contour is much narrower than the experimental one. In search for the reasons of this discrepancy between calculations and experiment, an analysis of relative rotational motion of acridine moieties of the dimer was carried out. It was found that minima of potential energy curves for rotational motion, although very flat, under conditions of supersonic expansion can acquire (in their shallow local minima) non-vanishing population of slightly different conformations of the dimer. It was shown that in terms of non-statistical distribution of such populations, the origin bands of individual conformations may contribute to the experimental band contour. |
| DOI: 10.12693/APhysPolA.100.845 PACS numbers: 33.20.Sn, 33.70.--w |