Laser pulse induced multi-exciton dynamics in molecular systems

Ultrafast optical excitation of an arrangement of identical molecules is analyzed theoretically. The computations are particularly dedicated to molecules where the excitation energy into the second excited singlet state E(S-2) - E(S-0) is larger than twice the excitation energy into the first excited singlet state E(S-1) - E(S-0). Then, exciton- exciton annihilation is diminished and resonant and intensive excitation may simultaneously move different molecules into their first excited singlet state vertical bar S-1 > . To describe the temporal evolution of the thus created multi- exciton state a direct computation of the related wave function is circumvented. Instead, we derive equations of motion for expectation values formed by different arrangements of single- molecule transition operators |S-1 > < S-0|. First simulation results are presented and the approximate treatment suggested recently in 2016 Phys. Rev. B. 94 195413 is evaluated.