Enhanced Triplet Formation in Polycrystalline Tetracene Films by Femtosecond Optical-Pulse Shaping

Polycrystalline tetracene films have been explored using weak similar to 30 fs visible laser pulses that excite the lowest singlet exciton as well as coherent vibrational motion. Transient difference spectra show a triplet absorption which arises following singlet fission (SF) and persists for 1.6 ns without decay. Adaptive pulse shaping identifies multipulse optimal fields which maximize this absorption feature by similar to 20%. These are comprised of subpulses separated by time delays well correlated with the period of lattice vibrations suggesting such modes control the yield of SF photochemistry.