Two Types of Mass Abundance Distributions for Anionic Carbon Clusters Investigated by Laser Vaporization and Pulsed Molecular Beam Techniques

Two types of mass spectra for anionic carbon clusters C^-_n have been revealed using laser vaporization and pulsed molecular beam techniques. The less structured mass spectrum characteristic of the magic-numbers at n = 5, 8, 11, 15, and 17 is established at the early stage of the cluster formation process, namely, in the laser vaporization process. The more structured one is featured for a regular odd-even alternation and the magic numbers at n =10, 12, 16, 18, 22, and 28, and has been developed only after extensive clustering and qnenching processes, where low-energy electron attachment plays a vital role. Transition between these two types of mass spectra can be realized by controlling either the strength of the pulsed gas flow or the synchronism between the gas flow and the laser vaporization.