The role of the metastable O₂(b${{}^{1}}{\Sigma}_{\text {g}}^{+}$ ) and energy-dependent secondary electron emission yields in capacitively coupled oxygen discharges

The role of surface quenching of the singlet delta molecule in a capacitively coupled oxygen discharge

“…In our earlier work we added oxygen atoms in the ground state O( 3 P) and ions of the oxygen atom O + and the relevant reactions to the oopd1 discharge model [39]. Later we added the singlet metastable molecule O 2 (a 1 ∆ g ), the metastable oxygen atom O( 1 D) [26], and the singlet metastable molecule O 2 (b 1 Σ + g ) [28], along with energy dependent secondary electron emission coefficients for oxygen ions and neutrals as they bombard the electrodes [28]. For this current work the discharge model contains nine species: electrons, the ground state neutrals O( 3 P) and O 2 (X 3 Σ − g ), the negative ions O − , the positive ions O + and O + 2 , and the metastables O( 1 D), O 2 (a 1 ∆ g ) and O 2 (b 1 Σ + g ).…”

“…For this current work the discharge model contains nine species: electrons, the ground state neutrals O( 3 P) and O 2 (X 3 Σ − g ), the negative ions O − , the positive ions O + and O + 2 , and the metastables O( 1 D), O 2 (a 1 ∆ g ) and O 2 (b 1 Σ + g ). The full oxygen reaction set and the cross sections used have been discussed in our earlier works and will not be repeated here [26,28,39]. However, as the role of the singlet metastable oxygen molecule O 2 (a 1 ∆ g ) is being explored two important reactions are mentioned here (see further discussion in Gudmundsson and Lieberman [26]).…”

“…We also note that the quenching probability for O 2 (b 1 Σ + g ) is in general significantly higher than for O 2 (a 1 ∆ g ). In our earlier studies [25,[27][28][29]32] we have used a quenching coefficients for the singlet metastable O 2 (a 1 ∆ g ) on the electrode surface of γ wqa = 0.007, estimated by Sharpless and Slanger for iron [49]. As the measured wall quenching probability for O 2 (a 1 ∆ g ) on aluminum is lower than for iron, as seen in Table II, we would expect that aluminum electrodes would therefore lead to higher singlet metastable densities and lower electronegativity.…”

On electron heating in a low pressure capacitively coupled oxygen discharge

“…In our earlier work we added oxygen atoms in the ground state O( 3 P) and ions of the oxygen atom O + and the relevant reactions to the oopd1 discharge model [26]. In subsequent studies we added the singlet metastable molecule O 2 (a 1 ∆ g ) and the metastable oxygen atom O( 1 D) [19], and the singlet metastable molecule O 2 (b 1 Σ) [21], to the reaction set. Furthermore, the discharge model now includes energy dependent secondary electron emission coefficients for oxygen ions and neutrals as they bombard the electrodes [21].…”

“…In subsequent studies we added the singlet metastable molecule O 2 (a 1 ∆ g ) and the metastable oxygen atom O( 1 D) [19], and the singlet metastable molecule O 2 (b 1 Σ) [21], to the reaction set. Furthermore, the discharge model now includes energy dependent secondary electron emission coefficients for oxygen ions and neutrals as they bombard the electrodes [21]. For this current work the discharge model contains nine species: electrons, the ground state neutrals O( 3 P) and O 2 (X 3 Σ − g ), the negative ion O − , the positive ions O + and O + 2 , and the metastables O( 1 D), O 2 (a 1 ∆ g ) and O 2 (b 1 Σ + g ).…”