Highly accurate intensity factors of pure CO 2 lines near 2 μm

• Published in: The Journal of chemical physics 2017-06, Vol.146 (24), p.244309
• Main Authors: Odintsova, T A, Fasci, E, Moretti, L, Zak, E J, Polyansky, O L, Tennyson, J, Gianfrani, L, Castrillo, A
• Format: Article
• Language: English
• ISSN: 1089-7690

Line intensities for carbon dioxide are measured with a novel spectroscopic approach, assisted by an optical frequency comb synthesizer for frequency calibration purposes. The main feature of the spectrometer consists in the exploitation of optical feedback from a V-shaped high-finesse optical resonator to effectively narrow a distributed feedback diode laser at the wavelength of 2 μm. Laser-gas interaction takes place inside an isothermal cell, which is placed on the transmission from the cavity. High quality, self-calibrated, absorption spectra are observed in pure CO samples at different gas pressures, in coincidence with three lines of the R-branch of the ν + 2ν + ν band. Line intensities are determined using a global fitting approach in which a manifold of spectra are simultaneously analyzed across the range of pressures between 5 and 100 Torr, sharing a restricted number of unknown parameters. Various sources of uncertainty have been identified and carefully quantified, thus leading to an overall uncertainty ranging between 0.17% and 0.23%. The measured values are in a very good agreement with recent ab initio predictions.