DUAL PATHWAY OF CARBON CLUSTER FORMATION IN THE LASER VAPORIZATION

The existence of two groups of carbon clusters in laser vaporization w as confirmed by the covariance analysis and laser fluence dependence s tudy. One is the clusters produced when the higher laser fluence is us ed, which most likely causes an atomization of graphite directly or ve ry rapid-and-intense fragmentation of large carbon particles. And the vaporized atoms or small clusters grow to larger clusters by the confi nement and clustering in the buffer gas. These clusters showed smooth ion distribution both for the cations and anions in the size region up to about a hundred. The other is produced when the laser fluence is l owered, These clusters showed the characteristic ion distribution with magic sizes at C-60(+), C-70+( )cations, and C-10(-), C-12(-), C-16(- ), C-18(-),... anions. The origin of the clusters was suggested as the large hot clusters which lead to the fragmentation into these smaller clusters observed. (C) 1997 American Institute of Physics.