LBT spectra of 16 stars

Toward BD+31 643, we determine an upper limit of (14+/-11)x10^12^cm^-2^ for the column density of C60, and values in the range of 10^12^-10^14^cm^-2^ toward other stars. Using literature data for C60+, we derive upper limits of 0.8-3.8 for the C60:C60+ column density ratios. The non-detection of the {gamma}0 absorption band toward BD+31 643 is in conflict with a measurement employing infrared (IR) emission bands of C60.

The discrepancy may indicate that free C60 molecules are not the source of the observed IR emission bands toward the star and that the IR emission arises from C60 molecules in dust grains instead. Alternatively, the oscillator strength of the {gamma}0 band may not be well constrained from the laboratory measurements.