Electron-ion bremsstrahlung spectra calculations for sonoluminescence

The bremsstrahlung spectra arising from electron-ion collisions are calculated for temperatures from 5000 K to 40 000 K and wavelengths from 100 nm to 1000 nm, for the ions He+, Ne+, Ar+, Kr+, Xe+, H+, and O+, using Hartree-Fock-Slater potentials. The spectral intensities are expressed in terms of Gaunt factors, the ratios of the present quantum computation and existing semiclassical results. For the heavy rare gas ions Gaunt factors of up to 3 are obtained at wavelengths of 200 nm. We use these results to improve our calculations of rare gas sonoluminescence spectra [Phys. Rev. E 65, 046309 (2002)] and find that the improved overall sonoluminescence spectra hardly differ from our earlier results which were based on the semiclassical treatment of the electron-ion bremsstrahlung contributions. We think that in the conventional single-bubble sonoluminescence studies electron-ion bremsstrahlung amounts to but a small percentage of the overall emission. We also estimate here the effects of shielding of the ions due to a finite Debye length. Unless the Debye length is smaller than about 50 bohr, no significant influence of Debye shielding is discernible.