IR SPECTROSCOPY INVESTIGATION OF PURIFIED ENDOHEDRAL Li@C_(60) AND Li@C_(70)

摘要

IR investigations have been carried out on purified Li@C_(60) fractions and Li@C_(70) produced by low energy ion implantation of C_(60) and C_(70) respectively. IR spectra of two Li@C_(60) fractions show similar features with respect to peak positions, especially in the higher frequency range. However, for the second Li@C_(60) fraction these modes exhibit additional splitting, indicating a reduction of its molecular symmetry with respect to the first endohedral fraction. IR spectra of the second Li@C_(60) fractions prepared with ~6Li and ~7Li isotopes are identical except for the position of broad bands at ca. 450-600 cm~(-1), originating from vibrational-rotational movement of the Li inside the carbon cage. The IR spectrum of Li@C_(70) is similar C_(140), but shows some extra peaks due to mode splitting.