2001ApJS..135..263S

Low-temperature gas-phase wavelengths and bandwidths for astronomical searches for C₆₀ in the 2400-4100 Å region are determined from the absorption spectra of C₆₀ in rare gas matrices at 4 K, coupled with information on the dependence of the vibronic transition frequencies of this fullerene on the Lorentz-Lorenz polarizability parameter of matrices and solvents. These bandwidths increase from 25±5 cm^–1 for the 1 ¹T_1u-1 ¹A_g band at 4024.0±0.5 Å to 2300±200 cm^–1 for the 6 ¹T_1u-1 ¹A_g band at 2488±8 Å. Spectral observations of astrophysical objects considered to be likely sites of C₆₀ have been examined in the context of the wavelengths and bandwidths of bands of the allowed transitions of C₆₀ which we recommend for searches of this species. No certain positive assignment of a C₆₀ band has been made in the 2400-4100 Å spectral region of these objects. The physical origin of the observed C₆₀ absorption bandwidths is analyzed and discussed in an appendix.