由激光蒸发石墨产生的碳原子簇等离子体的质谱研究

Mass Spectrometry of Carbon Cluster Plasma Produced with Laser Vaporization of Graphite

以脉冲激光蒸发石墨样品,可以产生含有多至1200个碳原子的原子簇正负离子。根据不同大小的碳原子簇离子的相对信号强度在质谱中的变化,可以分析出碳原子簇构型随着簇原子数的增加,所发生的从链状至平面环状再至空间封闭体的转化。

Using pulsed laser vaporization of graphite sample, both positive and negative ions of carbon clusters with cluster size up to 1200 can be generated routinely. The cluster ions were then analyzed on a time-of-flight mass spectrometer.lt is found from the mass spectra that those cluster ions no longer keep their original structure of bulk sample.Extensive structure re-organization might occur in the laser vaporization process, and fragmentations followed as they diffused into the acceleration region of the spectrometer.By studies of the ion intensity as a function of cluster size, a structure conversion of carbon cluster from chain to planar ring with cluster size of 13 can be infered from the mass spectra.For clusters containing more than 30 carbon atoms, they may have closure structures. Among them, C_(60) was previously prosposed to have a perfect football structure. Studies reported in this paper support the presumption, but also showed that this super-stable cluster can be generated in a laser plasma instead of a supersonic molecular beam.