Figure 2: Intrapulse chirp spectroscopy. (a) Data from the reference channel, without CO absorption (dashed line) and the sample channel (full line) featuring CO absorption, respectively. (b) Etalon transmission signal seen by detector 1 with the etalon placed in the reference beam path. (c) Etalon transmittance curve. (d) Data of (a), converted to absorbance values (open circles). A Voigt profile has been fitted to the data (full line) representing the CO-P(1) line at 2139.4261 cm−1 [18].