High-resolution oscillator strength measurements of the CO B ¹Σ⁺-Χ ¹Σ⁺ (0, 0) and (1, 0) vibrational bands

Large discrepancies in the published photoabsorption oscillator strengths of the vacuum-ultraviolet (VUV) bands of CO hamper the interpretation of VUV astronomical observations. We report new oscillator strength measurements of the (0, 0) and (1, 0) bands of the CO B ¹Σ⁺-Χ ¹Σ⁺ electronic system determined from high-resolution (resolving power ≈750,000) absorption spectra recorded with a tunable VUV laser system. The instrumental bandwidth (∼0.14 cm^-1 FWHM) was significantly less than the widths of the Doppler-broadened CO lines (∼0.20 cm ^-1 FWHM). The Β(0)-Χ(0) and Β(1)-Χ(0) band oscillator strengths, derived from measurements of the photoabsorption cross sections of 36 individual rotational lines, are (6.5 ± 0.6) × 10^-3 and (1.1 ± 0.1) × 10^-3, respectively. Our results are compared with other recent laboratory measurements and with ab initio calculations.