Intensity and self-broadening coefficient measurements from Fourier transform spectra : application to the nitric oxide fundamental band

Several absorption Fourier Transform spectra (resolution 2.7 × 10–3 cm–1) of the 15N16O and 14N16O isotopic species of nitric oxide, have been used to obtain intensities and self-broadening coefficients for lines near 5.4 µm. To accurately take into account the effect of the Λ-type splitting in the determination of individual intensities of each component from observed total equivalent widths, an extension of the usual curve of growth method is proposed. It is proved that such an improvement of the method does avoid a systematic 33 % error in the measurements. 84 intensities obtained in this way are reported for the Λ-doublets of the 15N16O 1 ← 0 allowed sub-bands, with an average uncertainty of about ± 8 %. 50 intensities for lines belonging to the well resolved Λ-doublets of the 15N16O 1 ← 0 forbidden sub-band are given, as also intensities of 22 Λ-doublets of the 15N16O 2 ← 1 band. Intensities of 64 Λ-doublets of the 14N16O 1 ← 0 allowed sub-bands are proposed. A method is presented to deduce the collisional-broadening coefficient of absorption lines from their depth, measured on Fourier Transform spectra. 107 self-broadening coefficients obtained in this manner are reported for line of the 15N16O 1 ← 0 forbidden sub-band, with an estimated uncertainty varying from ± 15 % to ± 25 % according to the line. Comparisons with previous measured or calculated strengths and widths are also established