High-sensitivity ESR studies of $trans-{\left(\mathrm{CH}\right)}_x$ have been carried out during photoexcitation with $\hslash \omega >E_g$. The results set an upper limit on the number of photoinduced unpaired spins, which is more than 2 orders of magnitude smaller than the number of charged excitations photogenerated under the same experimental conditions. We conclude that the charged photoexcitations are spinless and therefore have the reversed spin-charge relation of solitons. The photogeneration branching ratio, neutral solitons to charged solitons, is less than ${10}^{-2\mathrm{}}$.

• Received 25 April 1983

DOI:https://doi.org/10.1103/PhysRevB.28.2356