Computational simulation of ionization processes in single-bubble and multi-bubble sonoluminescence

The most recent spectroscopic studies of moving-single bubble sonoluminescence (MSBSL) and multi-bubble sonoluminescence (MBSL) have revealed that hydrated electrons (e_\rm aq^-) are generated in MSBSL but absent in MBSL. To explore the mechanism of this phenomenon, we numerically simulate the ionization processes in single- and multi-bubble sonoluminescence in aqueous solution of terbium chloride (TbCl_3). The results show that the maximum degree of ionization of single-bubble sonoluminescence (SBSL) is approximately 10000 times greater than that of MBSL under certain special physical parameters. The hydrated electrons (e_\rm aq^-) formed in SBSL are far more than those in MBSL provided these electrons are ejected from a bubble into a liquid. Therefore, the quenching of e_\rm aq^- to SBSL spectrum is stronger than that of the MBSL spectrum. This may be the reason that the trivalent terbium Tb(III) ion line intensities from SBSL in the TbCl_3 aqueous solutions with the acceptor of e_\rm aq^- are stronger than those of TbCl_3 aqueous solutions without the acceptor of e_\rm aq^-. Whereas the Tb(III) ion line intensities from MBSL are not variational, which is significant for exploring the mechanism behind the cavitation and sonoluminescence.