ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The excitation polarization (EP) spectra of fluorescence of pyrazine, pyrimidine, and s-triazine in the vapor phase have been obtained at room temperature along the rotational contour of the absorption bands belonging to the S0→S1 transition. The decay curves of the parallel and perpendicularly polarized fluorescence of these molecules have also been observed. At low pressures, the degree of polarization of both fast and slowly decaying components of fluorescence emitted from the initially prepared vibronic level (IPL) exhibits a remarkable variation along the rotational contour in every case, whereas the broad fluorescence of pyrimidine and s-triazine emitted from the levels to which nonradiative transition occurs from the IPL is not polarized with excitation to any rotational level. The EP spectra of the IPL fluorescence are well reproduced theoretically by considering the resonance fluorescence from fully resolved rotational levels in S1 and by employing a symmetric top approximation. The EP spectra of the broad fluorescence are also reproduced fairly well by assuming that K scrambling occurs within the singlet manifold following the intramolecular vibrational redistribution from the IPL and that the broad fluorescence is emitted from such K scrambled levels. On the basis of these results, polarization characteristics of fluorescence and the role of molecular rotation in the intramolecular dynamics of these molecules are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.454487
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