Fs-dynamics of charge-transfer excited states in anthracene–PMDA single crystals

Single crystals of the weak charge-transfer (CT) complex anthracene–PMDA have been studied by fs transient absorption spectroscopy in the temperature range between 295 and 10 K. Upon variation of the probe light polarization the complete set of transient CT-signals is identified (transient absorption of the CT-state, stimulated emission and transient bleaching), for the first time in CT single crystals. The formation of the CT-state after photoexcitation occurs faster than 150 fs without precursor, independent of temperature and excitation energy. An additional transient signal is clearly differentiated and described quantitatively by dipole-induced shifts of the ground state absorption.