Correlation between Na* emission and "chemically active" acoustic cavitation bubbles.

The emission from electronically excited sodium atoms (Na*) from aqueous solutions containing NaCl or sodium dodecylsulfate under ultrasonic irradiation is studied. Evidence is presented that strongly suggests Na* emission arises from a population of bubbles that are sonochemically active but not producing sonoluminescence (SL). Results indicate that the Na* emission intensity is mainly dependent on the concentration of Na(+) ions near the bubble/solution interface. The results provide further insight into the origin of alkali metal spectral line emission from sonicated aqueous solutions containing sodium ions.