Measurement of oxygen atom density employing vacuum ultraviolet absorption spectroscopy with microdischarge hollow cathode lamp

The compact measurement system for absolute density of oxygen (O) atom has been developed, which employs a vacuum ultraviolet absorption spectroscopy (VUVAS) technique with a high-pressure microdischarge hollow cathode lamp (MHCL) as a light source. The influences of self-absorption, emission line profile of the MHCL, and background absorption of oxygen molecule (O-2) on the determination of absolute O atom density were taken into consideration. This system has been applied for measuring absolute O atom densities in an inductively coupled O-2 plasma. O atom densities were estimated to be on the order of 1x10(12)-1x10(13) cm(-3) at an input power of 100 W and an O-2 pressure ranging from 1.3 to 26.7 Pa. The behavior of O atom density measured using VUVAS technique was consistent with that obtained by actinometry technique using O emission intensities of 844.6 nm and 777.4 nm lines. Moreover, the lifetime of O atom in the afterglow plasma has been measured. The decay curves of the O atom density were fitted with exponential functions. The extinction process of O atom in the inductively coupled O-2 plasma has been discussed. (C) 2003 American Institute of Physics.