Gas Component Identification for Laser-Induced Cavitation Bubbles

Cavitation bubbles can be generated by focusing a pulsed laser, which involves a large variety of physical/chemical phenomena. The products (e.g., reactive chemical species, shock waves), especially at the collapse phase, are associated with the energy partition. The identification of gas components inside the cavitation bubble is an important step to reveal the bubble dynamics and energy partition during the bubble oscillation. In this study, we experimentally explored to identify the gas components within laser-induced cavitation bubbles. High voltage was introduced into the cavitation bubble through a needle electrode and homogenous plasma discharge inside the bubble was observed. Spectroscopy analysis of the plasma emission lines, suggesting the persistent existence of water vapor, confirms the importance of initial dissolved gases in the water. This study also found that the additional energy from plasma discharge can significantly enlarge the rebound bubble size.