The transduction of sound into light through the implosion of a bubble of gas leads to a flash of light whose duration is delineated in picoseconds. Combined measurements of spectral irradiance, Mie scattering, and flash width (as determined by time-correlated single-photon counting) suggest that sonoluminescence from hydrogen and noble-gas bubbles is radiation from a blackbody with temperatures ranging from 6000 K (H2) to 20,000 K (He) and a surface of emission whose radius ranges from 0.1 µm (He) to 0.4 µm (Xe) . The state of matter that would admit photon–matter equilibrium under such conditions is a mystery.
© 2001 Optical Society of America
G. Vazquez, C. Camara, S. Putterman, and K. Weninger, "Sonoluminescence: nature’s smallest blackbody," Opt. Lett. 26, 575-577 (2001)