O2(a1Δg) absorption and O2(b1g+) emission in solution: Quantifying the a-b stokes shift

Tamás Keszthelyi, Tina D. Poulsen, Peter R. Ogilby, Kurt V. Mikkelsen

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In a nanosecond time-resolved infrared spectroscopic study of dissolved oxygen, O2(a1Δg) absorption, i.e., a1Δg→b1g +, and O2(b1g+ emission, i.e., b1g+→+ a1Δg, were monitored at ∼5200 cm-1 in a number of solvents. The maxima of the respective spectra depend significantly on the solvent, indicating that the O2(a1Δg) and O2(b1g+) energy levels likewise depend significantly on the solvent. The corresponding Stokes shifts, however, are small. The latter, recorded as the difference between the absorption and emission maxima, do not exceed the uncertainty limits that derive from the step-scan Fourier transform spectroscopic measurements (∼ ±3 cm-1)- Nevertheless, the data clearly indicate that the difference between the equilibrium and nonequilibrium solvation energies for the O2(a1Δg) and O2(b1g+) states is not large. Within the error limits, it is not possible to ascertain if the Stokes shifts are solvent dependent. Ab initio computational methods were used to model the data, and the results indicate that both long- and short-range interactions between oxygen and the perturbing solvent must be considered to adequately describe spectroscopic transitions in dissolved oxygen. The computational results indicate that a 1:1 complex between oxygen and the perturbing molecule embedded in a dielectric continuum appears to provide a sufficiently accurate model that can be used to probe subtle solvent-oxygen interactions.

Original languageEnglish
Pages (from-to)10550-10555
Number of pages6
JournalJournal of Physical Chemistry A
Issue number45
Publication statusPublished - Nov 16 2000

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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