Concomitance in single bubble sonoluminescence of period doubling in emission and shape distortion

•Shape distortion observed with Mie scattering in SBSL.•Experimental proof of long time stability of shape distortion.•Simultaneous period doubling in shape distortion and emission links the phenomena. We report the first direct observation for a single stable sonoluminescing bubble of a shape instability. Furthermore we show that stable saturation of the shape distortion caused by the instability for a certain range of parameters is experimentally possible and furthermore is directly linked to the curious phenomenon of flash by flash period doubling of the sonoluminescent emission as the afterbounce instability causing the shape distortion is always period doubled whenever the emission is & vice versa.