Small Carbon Clusters (Cn(0), Cn(+), Cn(-)) from Acyclic and Cyclic Precursors.Neutralization-Reionization Mass Spectrometry and Theory

摘要

Ab initio calculations of isomeric carbon clusters C sub n(0) and C sub n(+), n =2-4, yield structures and energies similar to previous reports, although five (not two) C4(+) structures have local energy minima. Dissociative ionization of structurally varied precursors was used to prepare C3 and C4 ionic and neutral isomers; however, their mass spectra from collisionally activated dissociation (CAD) and neutralization-reionization (NR) under a wide variety of conditions are indistinguishable, indicating only one isomer or the same mixture of isomers. Likewise, CAD and NR spectra of C4(+) and C4(0) from (13)CH2=CHCH=(13)CH2 and C3(+) and C3(0) from CH2=(13)CHCH3 show complete (13)C/(12)C scrambling. CAD