Photophysics of buckminsterfullerene and friends

[摘要] This dissertation describes a series of photophysics experiments on buckminsterfullerene (C$sb{60}$), other fullerenes (C$sb{m n}$), and the metallofullerenes (C$sb{m n}$M). Photodissociation is performed in a tandem time-of-flight mass spectrometer. Mass isolated cluster ions are irradiated with a high fluence UV laser and the product ions are mass analyzed. All these clusters dissociate identically: the primary fragmentation event is loss of neutral C$sb2$. All fragmentation is multiphoton at 6.4 eV. Higher order fragmentation is by loss of an even numbered neutral carbon particle. This production of fullerene fragments stops at C$sb{32}$ for the pure carbon, and at a size which depends on the metal atom for the metal-carbon clusters. The fullerene product ions show stability at 50, 60, and 70, especially when produced in a long timescale metastable decay process. The spheroidal shell theory of carbon can explain all these results. This theory states that large even C$sb{m n}$ clusters have edgeless spheroidal cage structures with 12 pentagons and n/2-10 hexagons. C$sb2$ loss occurs because the transition state for C$sb3$ loss is not accessible. Stability at clusters with 28, 32, 50, 60, and 70 is a result of spherically distributed strain of curvature. C$sb{60}$ can perfectly distribute its strain explaining its dominance. The central cavity of these structures is large enough to complex a metal ion, but only down to a certain size.

[发布机构] Rice University