## 4 Conclusions  
We report CO\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\) and air-induced pressure broadening coefficients of the HCl P(5) line of the 1\(\leftarrow\)0 band at 2775.7 cm\({}^{-1}\) measured with a newly developed, highly sensitive Mid-IR ICL-based dTDLAS spectrometer. The measurements were performed in the pressure range of 100-600 mbar which is important for analytical instruments with a reduced measurement pressure to enhance chemical selectivity. Based on well-established TDLAS system in our group, and traceably calibrated pressure and temperature sensors, our results provide a new reliable and fully consistent set of experimental broadening parameters for the HCl P(5) (1\(\leftarrow\)0) line for five matrix gases obtained within the same \begin{table}
\begin{tabular}{c c c c c} \hline  & **This Work** & \multicolumn{2}{c}{**References**} & \multicolumn{2}{c}{**Scaled to 296 K**} \\  & & & & **(This Work/References)** \\ \hline \(\gamma_{\rm CO2}/10^{3}\) cm\({}^{-1}\)/atm & 76.42 \(\pm\) 0.83 & 74.2 \(\pm\) 2.2 [25] & & \\ Pressure/atm & 0.1–0.6 & 0.2–0.93 & & \\ Temperature/K & 295 & 296 & & 76.23/74.2 [24] \\ Relative uncertainty & 1.09\% & 3\% & & \\ \hline \(\gamma_{\rm N2}/10^{3}\) cm\({}^{-1}\)/atm & 60.92 \(\pm\) 0.63 & 60.9 \(\pm\) 0.5 [26] & 59.2 \(\pm\) 0.3 [30] & \\ Pressure/atm & 0.1–0.6 & 0.026–0.27 & \(\leq\)11 & \\ Temperature/K & 294 & 295 & 298 & 60.71/60.8 [25], 59.4 [26] \\ Relative uncertainty & 1.03\% & 0.8\% & 0.5\% & \\ \hline \(\gamma_{\rm Ar}/10^{3}\) cm\({}^{-1}\)/atm & 26.23 \(\pm\) 0.78 & 29.4 \(\pm\) 2 (meas.) & 27.8 [31] & \\ Pressure/atm & 0.1–0.6 & 10–50 & 3–5 & 26.19/27.89 [28] \\ Temperature /K & 295 & Room T & 298 & \\ Relative uncertainty & 2.97\% & 6.8\% & – & \\ \hline \(\gamma_{\rm O2}/10^{3}\) cm\({}^{-1}\)/atm & 34.50 \(\pm\) 0.73 & 31.9 \(\pm\) 0.3 [28] & 33.4 [29] & \\ Pressure/atm & 0.1–0.6 & 2–11 & \(\leq\)5 & 34.38/32.01 [29], 33.51 [30] \\ Temperature/K & 294 & 298 & 298 & \\ Relative uncertainty & 2.12\% & 0.9\% & – & \\ \hline \(\gamma_{\rm Air}/10^{3}\) cm\({}^{-1}\)/atm & 55.26 \(\pm\) 0.99 & 52.4 \(\pm\) 0.5 [28] & 54.1 \(\pm\) 0.3 [26] & \\ Pressure/atm & 0.1–0.6 & 2–11 & 0.026–0.27 & 55.09/52.56 [29], 54.02 [25] \\ Temperature/K & 294 & 298 & 295 & \\ Relative uncertainty & 1.79\% & 1\% & 0.6\% & \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of our results with data from the literature for the foreign broadening coefficients of HCl P(5) (1\(\leftarrow\)0) absorption line with CO\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\) and Air. instrument and evaluation process. Compared to the existing literature data several discrepancies were found and discussed. The relative accuracy of pressure broadening coefficients have been improved for HCl-CO\({}_{2}\) and HCl-Ar in comparison with the data from the literature. The newly measured HCl-O\({}_{2}\) and HCl-Air broadening coefficients have better consistency than the literature values. For HCl-Ar and HCl-O\({}_{2}\) broadening coefficients, data were only available from measured high pressures; this work's \"low pressure\" data is new. HCl-Ar, HCl-O\({}_{2}\) and HCl-Air broadening coefficients reveal systematic effects of super Lorentzian behavior for coefficients determined at higher pressures. Our novel results are therefore important for the development of analytical HCl instrumentation in all industrial and energy gas applications particularly in combustion emission monitoring, and will be very useful spectroscopic measurements where absorption line has to be fitted. Conceptualization, Z.Q., O.W. and V.E. Experiment realization and data collection, Z.Q. Data evaluation and discussion, all authors. All authors have read and agreed to the published version of the manuscript. This research was partially funded by the IMPRESS2 (16 ENV08) and the MetAMC2 (17 IND09) projects. These projects have received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. Not applicable.