A study of reversible photochemical phenomena in c60

We report Raman measurements on the photoinduced disassociation via a metastable excited state intermediate of the photoproduct formed from the photochemical degradation of C60. At low intensities, the intrinsic 1468cm-1 C60 mode softens to 1459cm-1, which is stable below an apparent threshold intensity above which it shifts abruptly to 1463cm-1. This mode is stable with increasing intensities. Upon a return to low intensities, the 1468cm-1 intrinsic C60 line reappears. The positioning of the Raman line at 1463cm-1 is associated with an excited state intermediate, observable only at high excitation densities.