X3Σg- → b1Σg+ Absorption Spectra of Molecular Oxygen in Liquid Organic Solvents at Atmospheric Pressure

Mikkel Bregnhøj, Ciaran K. McLoughlin, Thomas Breitenbach, Peter Remsen Ogilby*

*Corresponding author af dette arbejde

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

7 Citationer (Scopus)

Abstract

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.

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Vol/bind126
Nummer23
Sider (fra-til)3839-3845
Antal sider7
ISSN1089-5639
DOI
StatusUdgivet - 16 jun. 2022

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