dc.creator Spears, K. G. en_US dc.creator El-Manguch, Mahmoud en_US dc.date.accessioned 2006-06-15T13:47:54Z dc.date.available 2006-06-15T13:47:54Z dc.date.issued 1976 en_US dc.identifier 1976-RS-12 en_US dc.identifier.uri http://hdl.handle.net/1811/9757 dc.description Author Institution: Northwestern University en_US dc.description.abstract We have used time correlated photon counting with a mode-locked, cavity dumped cw laser to study the emission lifetimes from pyrimidine in its $^{1}B_{1}$ excited state. The emission exhibits a dual decay in all bands with two lifetimes in the range of 1 to 500 nsec. The 0-0 band shows a very small amount of shore lifetime, emission ($< 0.1%$ ) while bands at higher energies have dominant amounts of short lived emission. The long lifetime emission is easily trenched and the overall data fit a model of reversible intersystem crossing. Pyrimidine is vary near small molecule behavior in its 0-0 band and the lengthenend lifetime can be combined with analysis of the dual decay to give a natural radiative lifetime and individual rate constants for the forward and reverse crossings. These values vary with band energy above the origin and show that pyrimidine ranges from nearly small molecule singlet-triplet coupling to large molecule irreversible decay. We also report the high resolution excitation spectra of several absorption bands in which the emission was separated according to long and short lifetimes. Those excitation spectra reveal regions of stronger and weaker couplings as shown by the separate peak structure of each time region and their non-conformance to the absorption spectra. en_US dc.format.extent 151971 bytes dc.format.mimetype image/jpeg dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title DUAL LIFETIMES AND TIME SEPARATED EXCITATION SPECTRA OF PYRIMIDINE en_US dc.type article en_US
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