Sonoluminescence of Aqueous Solutions of CaCl2 and NaCl: The Effect of Concentration

The structure of the sonoluminescence spectra of argon-saturated aqueous solutions of CaCl2 and NaCl of various concentrations is considered in detail. The frequency of ultrasound is 20 kHz, and the output power is 18 W. The spectrum of the CaCl2 solution changes considerably as the concentration rises. The intensity of the continuum passes through a maximum near the saturation concentration. Atomic, ionic, and molecular metal lines are observed for medium concentration values and disappear at high concentrations. Similar behavior is displayed by the spectra of NaCl solutions. The differences between the spectra are explained by the change in the vapor-gas content of the bubbles and the nature of their population, from large and non-inertial to small and pulsating inertially.