Hydrodynamic Simulation And Spectra Determination In Aqueous H2SO4 Solutions Cavitation Bubbles.

Abstract

Light emission in single-bubble sonoluminescence (SBSL) experiments results from the extreme
conditions reached during the very strong collapse of a gas bubble driven into non-linear
radial oscillations. Recent experiments achieved an important enhancement (by a factor 2700)
in the light emitted from the bubble by using Argon bubbles within aqueous H2SO4 solutions.1
The very marked increase in SBSL intensity allowed well resolved spectra determination revealing
the presence of spectral lines coming from atomic (Ar) emission and other molecular and
ionic processes.
In the present work we calculate the hydrodynamic motion of the gas inside the bubble using
compressible Navier-Stokes equations in spherical symmetry in order to obtain instantaneous
temperature and density profiles. Taking the previous results as input we apply a spectral model
which incorporates atomic physics and takes into account the finite opacity of the gas under the
extreme conditions at bubble collapse. Results are in agreement with timescale of the light pulse
width and continuum part of experimental spectra measured.1 Besides we found that brighter
bubbles are not necessarily hotter bubbles. The full model presented constitutes an adequate
starting point for modelling line emission observed in experiments.