Sodium Atom Emission from Aqueous Surfactant Solutions Exposed to Ultrasound

Abstract

Emission from electronically excited sodium atoms (Na∗) was observed when argon saturated aqueous solutions of the anionic surfactants, sodium dodecyl sulfate, sodium octyl sulfate, sodium 1-pentanesulfonate, and sodium 1-octanesulfonate were sonicated using 358 kHz ultrasound. The same emission band, centered at about 590 nm, was also obtained in aqueous NaCl solutions, although a ∼100-fold higher concentration than that used for the surfactant solutions was required to obtain an emission of comparable intensity. The results have been interpreted in terms of the surfactant adsorbing at the gas-solution interface of the bubbles generated by the ultrasound, generating an electrostatic surface..