Low temperature raman spectra on tdae-c60 single crystals

Low-temperature single crystal Raman spectra are presented for the organic ferromagnetic insulator TDAE-C60. The mode intensities, lineshifts, linewidths and depolarization ratios are compared with alkali-doped fullerene materials and with pure C60. A comparison of visible laser light excited spectra (Eexc. = 2.41 eV) with infrared excited Raman measurements (Eexc. = 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 infraredwhich is resonant with the tm1u → t1g electronic transition —also the radial modes are observed to shift. The effect is attributed to Raman resonance with different relaxed states of C60 anion.