The absolute number density of oxygen atoms in the O(3P 2) state is determined in an inductively coupled plasma chamber using absorption spectroscopy enhanced by a high finesse cavity with a continuous wave diode laser as the radiation source. At a nominal pressure of 100 mTorr of precursor gas O2 and 500 W plasma power the O(3P 2) concentration is found to be (4.8 0.6) × 1014 cm-3. © 2007 IOP Publishing Ltd.
