3aPA2. Plasma diagnostics and sonoluminescence.

Session: Wednesday Morning, December 4

Time: 8:20

Abstract:

Plasma diagnostic techniques are applied to single- and multibubble sonoluminescence (SBSL and MBSL). In the case of SBSL the electronic temperature (T[inf e]) and density (N[inf e]) are deduced on basis of the spectrum of an Ar bubble in water [the recording by R. Hiller et al., Science 226, 248 (1994)]. This analysis, based on the emission continuum, reveals that the intracavity sonoluminescent medium behaves as a sparklike plasma highly charged with energy (T[inf e]=20 000 K; N[inf e]=10[sup 25] m[sup -3]). In the case of MBSL (Ar bubbles in water), the method of the ratio ``intensity of a line/intensity of the adjacent continuum'' is used in order to determine T[inf e]. The higher the ultrasonic frequency, the hotter the bubble interior is. Two scenarios are analyzed (plasmas with a degree of ionization 1%) and the order of magnitude of N[inf e] is estimated. The conditions associated with multibubble systems appear to be of the same kind as those associated with SBSL, with a lesser degree of intensity, however. The possibility is discussed that local thermodynamic equilibrium (LTE) or partial LTE is reached. [Work supported by F.N.R.S., Belgium.]