Influence of the molecular structure on heterocyclic-ring dissociation kinetics and structural evolution of laser-induced plasmas

Four azoles with similar element percentages but different heterocyclic rings and functional groups are investigated with fs laser-induced breakdown spectroscopy (LIBS) as regards the influence of the interaction between the functional groups and heterocyclic rings on laser-induced plasma (LIP) emission. Temporally and spatially resolved measurements of the CN and C2 emissions are obtained and analyzed. The functional group affects the π-electron delocalization of the heterocyclic ring and consequently changes the dissociation pathways of the heterocyclic ring. At the early stage, CN is formed from the atomic recombination or native fragments, while at the late stage, through the remaining native fragments. In the whole plasma lifetime, C2 is mainly transformed from CN. Furthermore, dynamic CN and C2 distributions mediated by the laser-induced shock waves are discussed.