Molecular emission and temperature measurements from single-bubble sonoluminescence.

Single-bubble sonoluminescence (SBSL) spectra in H2O show featureless continuum emission. From an acoustically driven, moving bubble in phosphoric acid (H3PO4), we observe very strong molecular emission from excited OH radicals (∼310  nm), which can be used as a spectroscopic thermometer by fitting the experimental SBSL spectra to the OH A 2Σ+ - X 2Π rovibronic transitions. The observed emission temperature (T(em)) ranges from 6200 to 9500 K as the acoustic pressure (P(a)) varies from 1.9 to 3.1 bar and from 6000 to >10,000  K as the dissolved monatomic gas varies over the series from He to Xe.