抄録
SL intensity varied with the concentration of glycerol, the frequency and power. Compared to pure
water, the pulse width becomes larger with increasing the concentration. The increase in the SL pulse width
may be associated with a viscous slowing of the bubble wall in the very last stages of the initial collapse. If the
compressive heating is still strong enough to result in plasma formation, the lowered wall velocity might allow
the plasma to remain intact and hot for a longer period of time than in pure water. For highly viscous solution
and only at 28 kHz and 50 kHz, we observed large bubbles of 100-300 μm in diameter. The large bubbles are
generated via the coalescence of 8-10 bubbles and keep stable because viscosity tends to stabilize the shape
anisotropy of large bubbles. Beside this large cluster bubbles, a number of tiny bubbles were observed, the size
of which is smaller than those in pure water. The multiple-peak pulses observed from NaCl solution of 80%
glycerol at 28 kHz are caused by the superposition of SL from the large cluster bubbles which radiate Na
emission.
