Pump–probe polarization anisotropy study of doubly degenerate electronic reorientation in silicon naphthalocyanine

Measurements with 26 fs pulses that cover the Q(0–0) band of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) yielded an initial anisotropy of 0.40 that decayed to 0.12 over 200 fs. This contradicts theories predicting anisotropy decay from 7/10 to 1/10. Including ground state bleaching and excited state absorption, anisotropy decay from 2/5 to 1/10 is predicted for degenerate electronic reorientation and dephasing.