Sonoluminescence of argon saturated alkali metal salt solutions as a probe of acoustic cavitation

Abstract

Emission from argon saturated aqueous alkali metal salt solutions is observed during insonation at 460 kHz. It is postulated to arise from de-excitation of excited alkali metal atoms formed by free radical reduction processes. In addition to the emission resonance lines, diffuse bands are observed at ∼554 nm and ∼740 nm for Na and K, respectively. The latter are due to emission from alkali metal–argon exciplexes and are known to occur when mixtures of alkali metal vapor and argon are rapidly compressed. An estimate of the cavitational temperatures and pressures is obtained by comparison of experimental emission band parameters with those derived theoretically.