Low temperature Raman spectra on TDAE-C-60 single crystals

Low-temperature single crystal Raman spectra are presented for the organic ferromagnetic insulator TDAE-C-60. The mode intensities, lineshifts, linewidths and depolarization ratios are compared with alkali-doped fullerene materials and with pure C-60. A comparison of visible laser light excited spectra (E-exc=2.41 eV) with infrared excited Raman measurements (E-exc=1.17 eV) shows a selective resonance effect whereby in the visible, a frequency shift of only the tangential modes is observed, while in the infrared which is resonant with the t(1u)-->t(1g) electronic transition - also the radial modes are observed to shift. The effect is attributed to Raman resonance with different relaxed states of C-60 anion.