Probing Luminescence from Aspherical Bubble Collapse

Abstract

The luminescence from single laser produced cavitation bubbles for varying degrees of asphericity is investigated temporally, spatially, and spectrally resolved. The degree of asphericity is controlled with an adjustable rigid boundary nearby the bubble. Temporally, single and multiple light emission events happen during a time interval of 80ns. The luminescence duration increases with increasing asphericity. Spatially, the emissions from aspherical collapsing bubbles display a pronounced halo around the central spot being several times larger than the luminescence from spherical collapse. Spectrally, the ratio of the line- to continuum emission of the sodium dublett is enhanced, whereas the total emitted energy decreases by four orders of magnitude as compared to the spherical collapse. These findings point towards emission not only from the bubble interior but also from the liquid surrounding the bubble exited by outgoing shock waves.