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

Abstract

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 1×1012–1×1013 cm−3 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.