Cumulative contributions of 3s-np (n≥3) transitions in comparing O atom densities in low-pressure Ar-O₂ and He-O₂ glow discharges

Many-fold enhancements in the population densities of O atoms in low-pressure glow discharges in Ar- O2 and He- O2 compared with the discharge in pure O2 have been reported in recent years. In some reports, the 3s S 3,5 -3p P 3,5 transitions of O atoms around 844.6 or 777.2 nm are considered in estimating the density of atomic oxygen. The authors' results demonstrate that the contributions of other possible transitions such as 3s S 3,5 -np P 3,5 (n>3) directly feeding the lower 3s S 3,5 levels are also significant and should be included for a better estimate of O atom densities.