Line parameters of the 4-0 band of carbon monoxide by high sensitivity cavity ring down spectroscopy near 1.2 µm

The high-accuracy spectroscopy of H2 rovibrational transitions in the (2-0) band near 1.2 μm

“…The recording procedure is similar to that adopted to measure D 2 transitions in the (2-0) band 26,29,30 except that an external cavity diode laser (ECDL) is used as a light source instead of distributed-feedback (DFB) laser diodes. The ECDL (Toptica fiber-connected DL pro, 1200 nm) was tuned to record small spectral intervals around the Q1–Q4, S0, and S1 transitions spanning the 7970–8605 cm −1 region.…”

“…Following ref. 27 and 29, a self-referenced frequency comb (Model FC 1500-250 WG from Menlo Systems) was used for the frequency calibration of the spectra. The frequency attached to each ring-down event is determined from (i) the frequency measurement of the beat note between a fraction of the ECDL light and a tooth of the frequency comb and (ii) the tooth number deduced from the frequency value provided by a commercial Fizeau-type wavemeter (HighFinesse WSU7-IR, 5 MHz resolution, 20 MHz accuracy over 10 hours).…”

“…25 and 26. The accurate frequency values associated ''on the fly'' to each ringdown event allow not only an absolute calibration of the frequency axis but also a reduction of the noise amplitude, in particular on the sharp slopes of the line profiles. 27,28 The recording procedure is similar to that adopted to measure D 2 transitions in the (2-0) band 26,29,30 except that an external cavity diode laser (ECDL) is used as a light source instead of distributed-feedback (DFB) laser diodes. The ECDL (Toptica fiber-connected DL pro, 1200 nm) was tuned to record small spectral intervals around the Q1-Q4, S0, and S1 transitions spanning the 7970-8605 cm À1 region.…”

Frequency comb-referenced cavity ring-down spectroscopy of natural water between 8041 and 8633 cm−1

“…As further checks of the accuracy of the frequency calibration of our spectra, we consider a few individual lines with line positions accurately measured in the literature. We first compared the water position values to those measured in low pressure CO spectra where water was present as an impurity [34]. The CO spectra were recorded by comb-reference CRDS with the same setup used in this work.…”