Picosecond sonoluminescence: An alternative electrohydrodynamic hypothesis

A mechanism is proposed for the sonoluminescence (SL) of single bubble in levitation in an acoustic field. The theoretical scenario is that during expansion and the major part of its collapse, a bubble is governed by Rayleigh-Plesset (RP) dynamics. Several ns before maximum collapse the bubble interface becomes unstable and ~10 to 20 needlelike jets are thought to invade the bubble symmetrically. Each of them releases a submicronic droplet. An intracavity spray is shed about 3 ns before the time of collapse. Because of the distortion of the electrical double layer surrounding the bubble, both jets and droplets are electrically (but oppositely) charged. The electrical field is so high that it is thought that electron emission occurs to such an extent that the jets are ablated and that a microplasma highly charged with energy is released within <50 ps (T⩾30000 K; N_e: 10²⁶ m^-3). The mechanism proposed is showed to apply to the case of bubbles in non-aqueous solvents, too