The dependence of the transient difference transmission spectrum on probe-light intensity was investigated for a blue-phase polydiacetylene with side groups of substituted urethanes. The spectra of stimulated emission and photoinduced absorption of the lowest 1Bu exciton were separately determined in the polymer, which exhibits extremely weak fluorescence with quantum efficiency < 10-5 and ultrashort lifetime of 140 fs, by "probe saturation spectroscopy" newly proposed here. The fluorescence spectrum calculated from the stimulated emission spectrum has a peak near 1.9 eV and is an approximate mirror image to the stationary absorption spectrum. The relaxation time constant from the higher excited state m 1Ag exciton to the lowest 1Bu exciton is estimated to be shorter than 50 fs.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry