Dynamics of a photo-excited state in polydiacetylene studied by femtosecond mid-infrared absorption spectroscopy

Relaxation dynamics of polydiacetylene was investigated with femtosecond time-resolved absorption spectroscopy between 1120 and 1280 cm−1. A new photo-induced IR band was found at 1225 cm−1 just after photo-excitation, and it disappeared with a decay time constant of 4.1±0.7 ps. This IR band is assigned to the vibrational mode which induces self-trapping of the 1B1u exciton.