On the far infrared bands associated to the vibration of multishell fullerenes

Multishell fullerenes could be produced in the circumstellar envelopes of rich carbon giants as proposed by Ugarte (1995) and could be carriers of diffuse interstellar bands. Here, we investigate a potential way to detect these molecules through the far infrared bands related to their vibrational spectra. Based on a surface continuum spherical description of the carbon shells, we have derived analytic expressions for their interaction potential and determined the vibrational frequencies of fullerenes in endohedral configurations. We find that their harmonic frequencies of oscillation lie in the range 20–65 cm−1. The associated bands could be observed with the spectroscopic facilities planned for the Far Infrared and Submillimeter Telescope (FIRST) providing a new way to confirm the existence of fullerenes in space. Suitable astronomical targets to search for these molecules are their likely sites of formation: carbon stars, post-AGB stars, protoplanetary nebulae, and dusty regions in the Galaxy.