Optical emission studies of laser desorbed C₆₀

The optical emission spectra of laser desorbed C₆₀ have been investigated as a function of laser fluence for desorption with a XeCl excimer laser (pulse length 20 ns). The observed spectra show close similarities to black-body radiation and can be fitted with the Planck black body formula (modified for small particles) thus giving information on the temperature of the desorbed species. The temperatures obtained (2300-3000 K) are in good qualitative agreement with previous, indirect temperature estimates. Spatially and temporally resolved measurements provide additional insight into the desorption mechanisms. An estimate of cooling rates indicates that thermionic electron emission and C₂ fragmentation dominate for temperatures above about 3000 K but below this value the dominant cooling mechanism is black-body radiation.