High-resolution one-photon absorption spectroscopy of the D2Σ−←X2Π system of radical OH and OD

Abstract Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the A 2 Σ + ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) , D 2 Σ − ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) and D 2 Σ − ( v ′ = 1 ) ← X 2 Π ( v ′ ′ = 0 ) bands of the OH and OD radicals generated in a plasma-discharge source using synchrotron radiation as a background continuum coupled with the VUV Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permitted the quantification of transition frequencies, relative f -values, and natural line broadening. The f -values were absolutely calibrated with respect to a previous measurement of A 2 Σ + ( v ′ = 0 ) ← X 2 Π ( v ′ ′ = 0 ) (Wang et al., 1979). Lifetime broadening of the excited D 2 Σ − ( v = 0 ) and D 2 Σ − ( v = 1 ) levels is measured for the first time and compared with previous experimental limits, and implies a lifetime 5 times shorter than a theoretical prediction (van der Loo and Groenenboom, 2005). A local perturbation of the D 2 Σ − ( v = 0 ) level in OH was found.