ABSTRACT As the plasma plume generated by nanosecond laser ablation of aluminum expands in ambient air, AlO molecules are formed through reactions between aluminum species in the plasma and oxygen‐containing species in the surrounding atmosphere. In this work, the emission characteristics of AlO molecules in 1064 nm nanosecond laser‐induced aluminum plasma were systematically investigated by time‐resolved optical emission spectroscopy. The influence of laser energy on the temporal evolution of AlO molecules was analyzed, and the plasma electron temperature was determined. At a fixed laser energy, the intensity of atomic Al emission decreases gradually with delay time, whereas the AlO molecular emission first increases and then decreases, reaching a maximum at about 20 μs. When the laser energy is increased from 30 to 70 mJ, the AlO molecules peak shifts to later delay times and the emission duration becomes longer. Meanwhile, the plasma electron temperature rises from about 4000 K to 5500 K. These findings show that the formation and evolution of AlO molecules are closely related to the thermal state and cooling process of the plasma, and provide useful insight into molecular formation and related plasma chemical reactions in laser‐induced plasma.
Chu et al. (Thu,) studied this question.