Example of the detected spectra for a time series measurement. The QCL is scanned by temperature with f = 10 mHz. The discharge is operated with 10% CO2 + He at 2 kHz with a voltage of 3 kV, current of ∼6 A, and a pulse length of 150 ns. The laser wavenumber tuning starts from 2288.34 cm-1 with a scanning rate of around 0.027 cm^-1/s. Etalon: light intensity with etalon to characterize the laser wavenumber; It0: transmitted light intensity with gas mixture but without discharge; I0: incident light intensity without gas mixture; It: transmitted light intensity with gas mixture and discharge.