Luminescence line narrowing in the low-temperature glassy phase of solid C60

Vibrational zero-phonon lines and structured sidebands are obtained at temperatures below 40 K in C60 films by narrow-band selective excitation with a cw Ti: sapphire laser. The large inhomogeneous broadening (about 130 cm−1) of the purely electronic transition (with a maximum at 733 nm) is explained by orientational disorder in the low-temperature glassy phase of solid C60. The peaks in the sidebands can be attributed to librational modes. The Debye—Waller factor was found to be 0.3.