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 (O2) 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 O2 plasma. O atom densities were estimated to be on the order of 1310– 1310 cm at an input power of 100 W and an O2 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 O2 plasma has been discussed. © 2003 American Institute of Physics. @DOI: 10.1063/1.1582386#