Excess vibrational energy dependence of quantum beats and fluorescence decay in molecules with intermediate case level structure:1B1pyrimidine with 0ndash;1300 cmminus;1excess energies

摘要

We have measured the biexponential decay and quantum beats from jethyphen;cooled pyrimidine excited to1B1(npgr;ast;). Single vibronic level excitation of theQbranch of ten vibronic levels produces observable quantum beats in the long component decay of almost all of these levels. Although the ratio of the preexponential factorsAf/Asbecomes progressively larger in a theoretically wellhyphen;understood manner, the quantum beat pattern remains deceptively simple for all the vibronic levels probed 0ndash;1300 cmminus;1above theS1band origin. We attribute this anomaly to a few levels strongly coupled to the optically prepared singlet resulting in the observed beat pattern, while a dense manifold of less strongly coupled levels dominates the characteristic intensities of the biexponential decay.