Time-resolved emission spectrometric study on laser ablated plasma from a La2O3 target

The composition and the evolution of the 355 nm laser ablated plasma from a La2O3 target both in vacuum and in ambient O-2 were investigated by using time - resolved emission spectrometry. Our results show that the excited La +* and LaO* are two main emission species. It is suggested that there are t wo pathways for the formation of LaO* in ambient O-2, one is the direct pro duction via laser - target interaction,and the other is the formation via t he oxidation of La and La+. The dependence of the delay time and the intens ity of the emission on the laser fluence,the observation distance away from the target surface, and the ambient O-2 pressure were examined. A kinetic model based on the interactions between the ablated species and the ambient O-2 is proposed to explain the experimental results satisfactorily. The me chanism of the plasma formation and evolution is also discussed.