Laser-induced molecular fluorescence diagnosis of aluminum monoxide evolution in laser-induced plasma

Molecular evolution in laser-induced breakdown spectroscopy (LIBS) is conventionally diagnosed by observing molecular spontaneous emission (SE). In this work, laser-induced molecular fluorescence (LIMF) was introduced to investigate molecular evolution in laser-induced plasma. Aluminium monoxide (AlO) was taken as a typical example for demonstration. AlO molecules in the X-2 Sigma(+) state were stimulated by a 484.82 nm laser beam, and then 510.21 nm fluorescence was observed. Compared with conventional SE in LIBS, the proposed LIMF demonstrated that it took more time to fully combine aluminum and oxygen atoms to AlO molecules. Moreover, the longer lifetime of the AlO in plasma was observed.