New method for isotopic ratio measurements of atmospheric carbon dioxide using a 4.3 μm pulsed quantum cascade laser

Rapid and Sensitive Quantification of Isotopic Mixtures Using a Rapidly-Swept External Cavity Quantum Cascade Laser

“…The isotopic precision observed with the swept ECQCL is comparable with the reported isotopic precision values obtained using DFB-QCL-based systems, such as for δ 13 C in CO2 [13,15], δ 15 N in N2O [12,20] and NO [18] and δ 18 O in H2O [14]. These isotopic precisions are reported over a broad range of integration times, sample concentrations and gas cell pressures, but generally fall within a ~0.1-10‰ range.…”

“…In this paper, the capability of a rapidly-swept ECQCL system to perform broadband isotope ratio measurements in transient sources, concentration ratio were calculated at integration times of 25 ms and 1 s, respectively. The isotopic precision found in this study is comparable to what has been reported for isotope ratio measurements using DFB-QCL-based systems [12][13][14][15]18,20], demonstrating the capability of a rapid broadband spectral acquisition approach for gas phase isotope ratio measurements in turbulent environments.…”

“…The 33‰ precision achieved in 25 ms demonstrates the capability for the swept ECQCL to be used for measuring isotopic ratios in turbulent and/or reactive plumes. Overall, the isotopic precision obtained from our open-path swept ECQCL studies is competitive with other isotope ratio measurements made using DFB-QCLs [12][13][14][15]18,20], demonstrating the capability of the broadband spectral measurement approach with an ECQCL when compared to the conventional two spectral line measurement approach. This broadband spectral measurement capability opens up the possibility for isotope ratio measurements of large molecules with broad rotationally-unresolved vibrational bands.…”

“…The measurements of isotope ratios in gas-phase chemical mixtures can be used to monitor physical and chemical processes relevant to atmospheric chemistry, biology, geology and medicine [10][11][12][13][14][15][16][17][18]. A number of distributed feedback (DFB)-QCL-based sensors have been developed to measure the isotope ratios in gas-phase chemical mixtures; however, due to the limited wavelength coverage offered by DFB-QCLs, the conventional scheme for isotope ratio measurement involves the measurement of two rovibrational transitions: one for each isotopologue/isotopomer [10,[12][13][14]17].…”

A liquid nitrogen-free preconcentration unit for measurements of ambient N<sub>2</sub>O isotopomers by QCLAS

“…They have the advantage of operating at non-cryogenic temperatures (quasi room-temperature) with high spectral purity and relatively high power output (Faist et al, 1994). The application of these light sources for high-precision isotope ratio measurement has been recently demonstrated for CO 2 by Nelson et al (2008) and Tuzson et al (2008a, b). Spectroscopy in the mid-IR region is particularly effective for molecules that exhibit strong fundamental vibrations, such as CO 2 and N 2 O, with line intensities about two orders of magnitude higher than in the near-IR.…”