TY - JOUR
T1 - X3Σg- → b1Σg+ Absorption Spectra of Molecular Oxygen in Liquid Organic Solvents at Atmospheric Pressure
AU - Bregnhøj, Mikkel
AU - McLoughlin, Ciaran K.
AU - Breitenbach, Thomas
AU - Ogilby, Peter Remsen
PY - 2022/6/16
Y1 - 2022/6/16
N2 - Spectra and absorption coefficients of the forbidden 765 nm X3ςg- → b1ςg+ transition of molecular oxygen dissolved in organic solvents at atmospheric pressure were recorded over a 5 m path length using a liquid waveguide capillary cell. The results show that it is possible to investigate this weak near-infrared absorption transition in a common liquid hydrocarbon solvent without the need for a potentially dangerous high oxygen pressure. Proof-of-principle data from benzene, toluene, chlorobenzene, bromobenzene, and iodobenzene reveal a pronounced heavy atom effect on this spin-forbidden transition. For example, the absorption coefficient at the band maximum in iodobenzene, (28.9 ± 3.3) × 10-3 M-1 cm-1, is approximately 21 times larger than that in benzene, (1.4 ± 0.1) × 10-3 M-1 cm-1. These absorption measurements corroborate results obtained from O2(X3ςg-) → O2(b1ςg+) excitation spectra of O2(a1Δg) → O2(X3ςg-) phosphorescence, which depended on data from a plethora of convoluted experiments. Spectroscopic studies of molecular oxygen in liquid solvents can help evaluate aspects of the seminal Strickler-Berg approach to treat the effect of solvent on Einstein's A and B coefficients for radiative transitions. In particular, our present results are a key step toward using the O2(X3ςg-) → O2(b1ςg+) transition to evaluate the speculated limiting condition of applying the Strickler-Berg treatment to a highly forbidden process. This latter issue is but one example of how an arguably simple homonuclear diatomic molecule continues to aid the scientific community by providing fundamental physical insight.
AB - Spectra and absorption coefficients of the forbidden 765 nm X3ςg- → b1ςg+ transition of molecular oxygen dissolved in organic solvents at atmospheric pressure were recorded over a 5 m path length using a liquid waveguide capillary cell. The results show that it is possible to investigate this weak near-infrared absorption transition in a common liquid hydrocarbon solvent without the need for a potentially dangerous high oxygen pressure. Proof-of-principle data from benzene, toluene, chlorobenzene, bromobenzene, and iodobenzene reveal a pronounced heavy atom effect on this spin-forbidden transition. For example, the absorption coefficient at the band maximum in iodobenzene, (28.9 ± 3.3) × 10-3 M-1 cm-1, is approximately 21 times larger than that in benzene, (1.4 ± 0.1) × 10-3 M-1 cm-1. These absorption measurements corroborate results obtained from O2(X3ςg-) → O2(b1ςg+) excitation spectra of O2(a1Δg) → O2(X3ςg-) phosphorescence, which depended on data from a plethora of convoluted experiments. Spectroscopic studies of molecular oxygen in liquid solvents can help evaluate aspects of the seminal Strickler-Berg approach to treat the effect of solvent on Einstein's A and B coefficients for radiative transitions. In particular, our present results are a key step toward using the O2(X3ςg-) → O2(b1ςg+) transition to evaluate the speculated limiting condition of applying the Strickler-Berg treatment to a highly forbidden process. This latter issue is but one example of how an arguably simple homonuclear diatomic molecule continues to aid the scientific community by providing fundamental physical insight.
UR - http://www.scopus.com/inward/record.url?scp=85131969591&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.2c03053
DO - 10.1021/acs.jpca.2c03053
M3 - Journal article
C2 - 35649157
SN - 1089-5639
VL - 126
SP - 3839
EP - 3845
JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
IS - 23
ER -