Sonoluminescence of elementary sulfur melt

The sonoluminescence of liquid sulfur has been observed for temperatures of 120–180°C. The sonoluminescence intensity of the sulfur melt is 10⁹ photons/s at 120°C. As the temperature increases, the luminescence intensity decreases nonmonotonically, a maximum is observed at 160–175°C, and cavitation and luminescence cease at 180°C. The dependence obtained correlates with the temperature dependence of the viscosity of the sulfur melt. The sonoluminescence spectrum obtained with a resolution of 10 nm for 130–150°C contains one band with λ_max = 560 nm, the emitter of which is likely an (S⁺)* ion. When the melt is saturated with argon, the sonoluminescence intensity increases by an order of magnitude; in this case, the spectral band shape changes only slightly. The results confirm the “electric” theory of multibubble sonoluminescence. In the process of the sonolysis of the sulfur melt, biradical fragments are formed in cavitation bubbles consisting of sulfur molecules, which initially have the form of cyclooctasulfur S₈. These fragments can enter into the melts and can be involved in various chemical reactions. This circumstance makes it possible to recommend ultrasonic activation for reactions of sulfurization of hydrocarbons.