•QCLs are promising spectroscopic sources for developing analytical instrumentation.•WMS is a sensitive spectroscopy technique for gas sensing.•A versatile QCL sensor based on dual spectroscopic techniques was developed for simultaneous measurement of multi-species.•Measurement precisions of 0.21 ppb for CO, 0.18 ppb for N2O and 5.65 ppm for H2O were achieved at the optimal averaging time of 75 s.A single continuous wave (CW) room-temperature (RT) quantum cascade laser (QCL) sensor based on dual spectroscopic techniques was demonstrated and developed for simultaneous measurement of atmospheric carbon monoxide (CO), nitrous oxide (N2O) and water vapor (H2O). The newly developed detection scheme combines the benefits of absolute concentration measurements using calibration-free direct absorption spectroscopy (DAS) with higher sensitive wavelength modulation spectroscopy (WMS), which offers the possibility of calibration-free trace gases concentration detection with a 3–4 fold improvement in measurement precision and a significant decrease in optimal signal averaging time. By using the DAS calibrated WMS-2f detection scheme, Allan deviation analysis indicates that measurement precision of 1.64 ppb for CO, 1.15 ppb for N2O and 50.4 ppm for H2O was achieved with a 1-s integration time, which can be further improved to 0.21 ppb, 0.18 ppb and 5.65 ppm by averaging up to 75 s.

•High resolution NIR spectra of acetylene were measured by TDLAS spectrometer.•Spectroscopic parameters of C2H2 near 1.525 μm have been revised for gas sensing.•Line intensities agreed at the −0.5% level by comparison to HITRAN12 database.Spectroscopic parameters of the ν1+ν3∑u+-0∑g+ bands of acetylene near 1.525 μm have been revised at room temperature. In the spectral region ranging from 6523 to 6587 cm−1, ten lines of C2H2 have been analyzed using a high resolution tunable diode laser absorption spectrometer. These transitions are well appropriate to the monitoring of acetylene by laser absorption spectroscopy. The Voigt model is used to fit the molecular absorption lineshape and to provide accurate spectroscopic line parameters. Our data have been found in agreement well with those given in the latest HITRAN database.

•Isotopic analysis is an attractive method for tracing the budgets of atmospheric trace gases.•QCLs are promising spectroscopic sources for developing analytical instrumentation.•Wavelength modulation spectroscopy is a powerful technique for gas sensing.•Site-selective 15N/14N ratio measurement with a precision of 3‰.The feasibility of laser spectroscopic isotopic composition measurements of atmospheric N2O was demonstrated, although making them useful will require further improvements. The system relies on a thermoelectrically (TE) cooled continuous-wave (CW) room temperature (RT) quantum cascade laser source emitting wavelength of around 4.6 μm, where strong fundamental absorption bands occur for the considered specie and its isotopomers. The analysis technique is based on wavelength modulation spectroscopy with second-harmonic detection and the combination of long-path absorption cell. Primary laboratory tests have been performed to estimate the achievable detection limits and the signal reproducibility levels in view of possible measurements of 15N/14N and 18O/16O isotope ratios. The experiment results showed that the site-selective 15N/14N ratio can be measured with a precision of 3‰ with 90 s averaging time using natural-abundance N2O sample of 12.7 ppm.Graphical abstract

•Mid-IR spectral region is of particular interest for atmospheric measurements.•QCLs are promising laser sources for spectroscopic applications.•H2O-broadening of two mid-infrared CO and N2O lines near 4.57 μm were measured.•H2O broadening coefficients are found to be 1.8 and 1.9 times higher than the corresponding air-broadening parameters.A tunable quantum cascade laser spectrometer (QCLS) was used to study H2O broadening coefficients for CO and N2O transitions at 4.57 μm region, which contains well-characterized and relatively isolated transitions of appropriate line strengths for sensitive gas detection. The influence of H2O broadening effect on CO R(11) and N2O P(38e) transitions at 2186.639 cm−1 and 2187.099 cm−1, respectively, was detailed investigated. Our measurements indicate that H2O broadening coefficients are 1.8 and 1.9 times higher than the corresponding air-broadening parameters, respectively. Based on the experimental data, our simulation confirmed that the WMS-2f shapes of CO and N2O lines will be significantly affected by variations of the water vapor mixing ratio, while no significant dependence on target concentration, and prove that the difference between air- and H2O-broadenings thus cannot be neglected if one wants to measure gas concentrations in a high humid environment with a sub-percent precision.