Line emission in single-bubble sonoluminescence

We report that single-bubble sonoluminescence (SBSL) at low light intensiti es produces emission bands similar to multibubble sonoluminescence (MBSL) f or pure noble gas bubbles. A smooth crossover between SBSL and MBSL behavio r can be induced by varying the acoustic pressure amplitude and thereby the intensity of the light emitted. The relative intensity of the band emissio n depends both on the molecular weight of the noble gas and the water tempe rature. Our results provide a connection between the mechanisms SBSL and MB SL and show that molecular emission plays a role in SBSL.