Open AccessStudies on the production of O 2 ( a 1 Δ g , υ = 0) and O 2 ( b 1 Σ g + , υ = 0) from collisional removal of O 2 ( A 3 Σ u + , υ ′ = 6–10)
Author(s) -
Pejaković Dušan A.,
Copeland Richard A.,
Cosby Philip C.,
Slanger Tom G.
Publication year - 2007
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007ja012520
Subject(s) - metastability , analytical chemistry (journal) , atomic physics , physics , yield (engineering) , ground state , ionization , production (economics) , relaxation (psychology) , chemistry , ion , social psychology , psychology , chromatography , quantum mechanics , thermodynamics , macroeconomics , economics
Production of two metastable O 2 species, O 2 ( a 1 Δ g , υ = 0) and O 2 ( b 1 Σ g + , υ = 0), from collisional removal of O 2 ( A 3 Σ u + ) by O 2 and N 2 is investigated at a temperature of 240 K. A state‐selective two‐laser technique is used, in which the output of the first laser excites ground‐state O 2 molecules to a specific vibrational level (6 ≤ υ ′ ≤ 10) in the A 3 Σ u + state, and the output of the second laser subsequently probes the O 2 ( a 1 Δ g , υ = 0) and O 2 ( b 1 Σ g + , υ = 0) populations by resonance‐enhanced multiphoton ionization via the intermediate d 1 Π g Rydberg state. For the relatively short timescales of our experiment (∼10 −4 Torr·s), we find that the O 2 ( a 1 Δ g , υ = 0) quantum yield from collisional removal of O 2 ( A 3 Σ u + , υ ′) by O 2 is approximately constant for υ ′ = 7–9, and decreases by 30–40% for υ ′ = 6 and 10. The O 2 ( b 1 Σ g + , υ = 0) yield is nearly constant for υ ′ = 8–10, and decreases by about 50% for υ ′ = 6 and 7. The eventual O 2 ( a 1 Δ g , υ = 0) and O 2 ( b 1 Σ g + , υ = 0) yields from O 2 ( A 3 Σ u + , υ ′ = 8) measured in synthetic air are nearly equal to those measured in pure O 2 , suggesting that N 2 collider does not significantly affect the relaxation pathways leading to the production of the two metastable species. However, at short experimental times the buildup of the O 2 ( a 1 Δ g , υ = 0) population is considerably slower in synthetic air than in O 2 .