Journal of Physical Chemistry A, Vol.106, No.23, 5582-5590, 2002
Photoluminescence of C-60 and its photofragments in the gas phase
The genuine photoluminescence spectrum of the S-1 state of C-60 was observed for the first time in the gas phase, using laser-induced fluorescence by photoexcitation at 266, 355, and 532 nm. The authenticity of the photoluminescence spectrum was confirmed by the sublimation enthalpy of the emitting species, the linear fluence dependence of emission intensity, the single exponential temporal decay of emission, and the constancy of the spectrum over different time delays and different excitation wavelengths. Upon increasing the laser fluence, drastically different emission features emerged. With photoexcitation at 266 nm, two spectral series with narrow bandwidths and fast decay times were observed on top of a broad emission band, which were identified as the Swan band and the Fox-Herzberg band of C-2 photofragmented from C-60. The broad band was deconvoluted into three component bands that persisted beyond time scales longer than a microsecond. In contrast, by photoexcitation at 355 nm, only the broad underlying emission was observed. From the fluence dependence and temporal profiles of the sharp and broad emission bands, generation mechanisms of the emitting species were proposed.