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1000 1200 1400 1600 RAMAN SHIFT ( cm"' )

Fig. 1130. (a) Room temperature first-order Raman spectrum for a C70 film on an Si (100) substrate [11.88], The Raman peak at =»520 cm"1 is associated with the Si substrate, (b) Room temperature first-order infrared spectrum of a C70 film on Csl. The arrows at the bottom of (b) denote infrared-active toluene modes, with the arrow length indicative of the mode intensity [11.8,81,151].

Fig. 1130. (a) Room temperature first-order Raman spectrum for a C70 film on an Si (100) substrate [11.88], The Raman peak at =»520 cm"1 is associated with the Si substrate, (b) Room temperature first-order infrared spectrum of a C70 film on Csl. The arrows at the bottom of (b) denote infrared-active toluene modes, with the arrow length indicative of the mode intensity [11.8,81,151].

C70 in terms of the difference in the moments of inertia parallel and perpendicular to the fivefold axis of C70 (see Table 3.2), they suggested that the orientational potential for C70 was weaker and more anisotropic than for Qo.

A molecular dynamics calculation of the intermolecular vibrations for C70 [11.153] yields a low energy for the lowest peak in the density of states (~1.2 meV) and a large linewidth (~0.9 meV), consistent with the experiments, but the calculated values are at considerably lower energy than

Table 11.8

Calculated modes for C7n and M6C,0 by force constant model [11.147],

Frequencies of the modes, even under reflection, expressed in cm-1

A[ modes A'2 modes E[ modes E'2 modes c7o M6C70 C70 M6C70 C7(1 M6C,0 C7ii M6C70

Frequencies of the modes, even under reflection, expressed in cm-1

A[ modes A'2 modes E[ modes E'2 modes c7o M6C70 C70 M6C70 C7(1 M6C,0 C7ii M6C70

230°

269"

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