SOLITONS IN DOPED BETA-CAROTENE FILMS - OPTICAL-ABSORPTION AND ESR STUDIES

We present optical absorption and electron spin resonance studies of iodine and AsF5 doped beta-carotene films. We show that stable soliton-like defects are formed upon p-doping. The spin to charge ratio found experimentally is congruent-to 0.02, indicating that nearly all defects are spinless. The absorption spectrum is characterized by a single intragap band and a set of infrared active vibration lines; evidence that there is significant structural relaxation upon charge transfer. A possible spinless species is the dication in which two soliton defects are, formed. The small number of spins observed are probably due to beta-carotene radical cations.