Effects of mixing He and Ar on single bubble sonoluminescence (SBSL)

Abstract

When a large pressure gradient is imposed in a gas mixture, a segregation of different species is expected to occur. Preliminary result of our search for segregation effects on the SBSL in ensonified water containing mixtures of 4He (partial pressure=pHe), Ar (pAr) and N2 (pN) gases will be presented. Deionized and initially degassed water was mixed with pHe+pAr=1.5 Torr and pN=148.5 Torr. The emitted light intensity I and the bubble radius dynamics (via Mie scattering) were measured as a function of the imposed 17.3 kHz acoustic drive amplitude for mixtures with varied x=pHe/(pAr+pHe). The acoustic pressure amplitude (Pa) at the bubble and the ambient bubble radius were extracted by fitting the Mie scattering data using Rayleigh–Plesset equation. In the range where SL occurs [Plo(x)<Pa<Phi(x)], the measured I increased linearly with Pa for x=0, 0.5, 0.75 and 1. The slope dI/dPa decreases with x. The results will be compared with expectations of homogeneous mixing of 4He and Ar and segregation in the SL bubbles.