High‐Resolution Oscillator Strength Measurements for High‐v′ Bands of theA1Π(v′)–X1Σ+(v″ = 0) System of Carbon Monoxide

Abstract

Band oscillator strengths for six bands of the CO A1Π(v')-X1Σ+(v'' = 0) system with 13 ≤ v' ≤ 21 have been determined from high-resolution (resolving power ≈ 750,000) absorption spectra recorded with a tunable vacuum ultraviolet (VUV) laser system. The instrumental bandwidth of the system, ≈ 0.11 cm-1 FWHM, was significantly less than the widths of the Doppler-broadened CO lines (≈ 0.20 cm-1 FWHM). Integrated cross sections of individual rotational lines were determined by a least-squares fitting routine, taking into account the effects of the finite instrumental resolution on the measured absorption features. Our derived f-values for the A(13)-X(0), A(14)-X(0), and A(16)-X(0) bands are consistent with other recent measurements, with the ab initio electronic transition moment calculations of Kirby & Cooper, and with f-values derived from the ab initio electronic transition moment calculations of Spielfiedel & Feautrier cited by Jolly et al. Our f-values for the A(18)-X(0), A(20)-X(0), and A(21)-X(0) bands, the first directly measured values for these bands, progressively deviate from band oscillator strengths derived from the electronic transition moment function of Kirby & Cooper. In addition, a pressure-broadening coefficient of (3.1 ± 0.6) × 10-4 cm-1 torr-1 was determined for room-temperature CO-CO collisions.