Spectral lines of OH radicals and Na atoms in sonoluminescence

With the equations of fluid mechanics, the proper boundary conditions, and the gas properties, we simulate the processes of single-bubble sonoluminescence. The calculation demonstrates the process of the evolution of the radiation energy spectrum with time for bright sonoluminescing bubbles, which clearly shows how the prominence of the OH line near 310 nm gradually merges into the continuous spectral background as the radiation power increases and finally disappears in the spectrum. For the dim bubble, the spectral line of OH radicals or the sodium line near 589 nm is prominent on the spectrum.