Crystalline ${\mathrm{C}}_{60}$, after exposure to air, is shown to exhibit the characteristic luminescence spectrum of singlet molecular oxygen. The role of oxygen is verified by measuring the large isotope shift of the ${\mathrm{O}}_2$ vibrational mode luminescence replica in a sample prepared with ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}_2^{}{}_{}{}^{}$. Detailed spectroscopy reveals novel bands in the spectrum which arise from vibronic coupling of the ${\mathrm{O}}_2$ transition to the ${\mathrm{C}}_{60}$ molecules. This allows measurement of the ${\mathrm{C}}_{60}$ vibrational spectrum with unparalleled sensitivity and precision from mg-sized samples.

• Received 12 June 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.2423