Absorption spectrum of singlet oxygen (a1Δg→b1Σg+) in D2O:: Enabling the test of a model for the effect of solvent on oxygen's radiative transitions

The time-resolved absorption spectrum of singlet molecular oxygen (a(1)Deltag --> b(1)Sigma(g)(+)) has been recorded in liquid D2O using a step-scan Fourier transform spectrometer. A molar absorption coefficient of 6 +/- 2 M-1 cm(-1) was determined for the peak of the absorption band at 5228 +/- 6 cm(-1). In this report, issues pertinent to the detection of this signal are outlined. Specifically, for O-2(a(1)Delta(g)) produced upon pulsed laser irradiation of a sensitizer, it is necessary to account for a laser-induced, temperature-dependent shift in a D2O absorption band that interferes with the weak a --> b signal. Along with a --> b absorption coefficients obtained previously in other solvents, the D2O data reported herein enable an appropriate test of a topical model for the perturbing effect of solvent on radiative. transitions in oxygen.