Polarized fs transient absorption of CT states in An-PMDA crystals—Excitonic strings?

Polarized sub-ps transient absorption spectra of anthracene-pyromellitic dianhydride charge-transfer (CT) single crystals reveal four different transient signal contributions. Three of these signals are directly related to the CT state and characterize an ultrafast generation process within 150 fs after photoexcitation. Particular emphasis is put on the different spectroscopic features and the origin of the fourth signal.