High-resolution study of oscillator strengths and predissociation rates for ¹²C¹⁶O: W-X bands and Rydberg complexes between 92.9 and 93.4 nm

Models of astronomical environments containing CO require accurate molecular data to reproduce and interpret observations. We are conducting experiments at the SOLEIL synchrotron facility to acquire data for modeling CO photochemistry in the vacuum ultraviolet. The improvement in UV spectroscopic instrumentation, both in sensitivity and resolution, provides more accurate laboratory spectroscopic determinations. We report new measurements yielding photoabsorption oscillator strengths and predissociation rates, for ¹²C¹⁶O at 295 K and 77 K, of four bands from X ¹Σ⁺ (v′′ = 0) to the v′ = 0-3 vibrational levels of the core-excited W ¹Π Rydberg state and for six overlapping bands between 92.97 and 93.35 nm. Absorption spectra were recorded using the vacuum ultraviolet Fourier transform spectrometer installed on the DESIRS beamline at SOLEIL, providing a resolving power R = 350 000. This resolution allows the analysis of individual line strengths and widths in the electronic transitions and the identification of a previously unobserved perturbation in the W(1) level. Gas column densities in the differentially- pumped system were calibrated using the B ¹Σ⁺-X ¹Σ⁺(0, 0) band. Absorption bands are analyzed by synthesizing line and band profiles with independently developed codes. These considerably improved results are compared with earlier determinations.