Spectra of Stable Non-Noble Gas Single Bubble Sonoluminescence
  A commonly accepted view is that stable Single Bubble Sonoluminescence (SBSL) can only be achieved in the presence of a noble gas or hydrogen. In air-seeded bubbles, the content of diatomic gasses is burned off to leave the small amount of argon needed to sustain stable operation. Here we report that long term stable SBSL can be sustained with only nitrogen, oxygen, or nitrogen/oxygen mixtures being present. Compared to that of a stable argon bubble, the emission is much weaker and the spectrum looks much colder. Oscillating states as well as recycling states are also observed. An intriguing saturation effect seems connected with the presence of water vapor in the bubble. 
Mogens T. Levinsen, Jeppe Seidelin Dam