Photoelectron spectroscopy and dynamics of excitons in C60 and photopolymerized C60 films

Pump-probe photoelectron spectroscopy is used to study excited states in pristine and photopolymerized C60. For the first time in a molecular solid, vibrationally broadened singlet (S1) and triplet (T1) exciton photoemission spectra are temporally isolated and unambiguously assigned. Complex transient behaviors of S1 and T1 populations, including non-Markovian decays and a strongly enhanced production of T1 states at high excitation, provide evidence for interactions among excitons and free carriers. A new rate-equation model reproduces a wide range of both laser- and synchrotron-based data from polymerized films.