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Fig. 1133. Effect of photoinduced dimerization and polymerization on the infrared and Raman spectra of C«,. The upper panel (a) shows infrared (A) and Raman (B) spectra for C«, taken with low incident optical power levels (<50 mW/mm2). The lower panel (b) shows the corresponding infrared (C) and Raman (D) spectra taken after exposure of the Cm film to intense optical power levels for several h, until the Raman line at 1469 cm"1 disappeared. After the intense optical irradiation, many more infrared and Raman lines appear in these spectra, due to a lowering of the symmetry caused by the photoinduced covalent bonding between the fullerene molecules [11.80].

modeled using molecular dynamics [11.155] and is in good agreement with experiment.

In Fig. 11.34 we see the Raman spectra for polymerized C60 in the vicinity of the pentagonal pinch mode for various temperatures. At the lowest temperature shown (65°C), the trace exhibits the characteristic spec-

Fig. 11.34. Raman spectra in the vicinity of the pentagonal pinch mode for a photochemically polymerized C«, film (d ~ 4500 A) on a Suprasil (fused silica) substrate for various temperatures. The dashed curves in the bottom spectrum represent a Lorentzian lineshape fit to each of the Raman lines in the spectrum at 65° C. As the temperature is increased, the features associated with the polymerized phase are quenched [11.156],

Fig. 11.34. Raman spectra in the vicinity of the pentagonal pinch mode for a photochemically polymerized C«, film (d ~ 4500 A) on a Suprasil (fused silica) substrate for various temperatures. The dashed curves in the bottom spectrum represent a Lorentzian lineshape fit to each of the Raman lines in the spectrum at 65° C. As the temperature is increased, the features associated with the polymerized phase are quenched [11.156],

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