High-resolution one-photon absorption spectroscopy of the D2Σ−←X2Πsystem of radical OH and OD

- Absolute f-values are measured for VUV bands of OH and OD.
- Line broadening indicates a lifetime of 20ps for the D2Σ−(v=0) and D2Σ−(v=1) levels.
- A local perturbation level of OH D2Σ−(v=0) causes level shifts and increased widths.

Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the A2Σ+(v′=0)←X2Π(v′′=0),D2Σ−(v′=0)←X2Π(v′′=0) and D2Σ−(v′=1)←X2Π(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 A2Σ+(v′=0)←X2Π(v′′=0) (Wang et al., 1979). Lifetime broadening of the excited D2Σ−(v=0) and D2Σ−(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 D2Σ−(v=0) level in OH was found.