TY - JOUR
T1 - Rapid and sensitive quantification of isotopic mixtures using a rapidly-swept external cavity quantum cascade laser
AU - Brumfield, Brian E.
AU - Taubman, Matthew S.
AU - Phillips, Mark C.
N1 - Funding Information:
Acknowledgments: This work was supported by the DOE/NNSA Office of Nonproliferation and Verification Research and Development (NA-22). The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy (DOE) by the Battelle Memorial Institute under Contract No. DE-AC05-76RL01830.
Publisher Copyright:
© 2016 by the author.
PY - 2016/6/1
Y1 - 2016/6/1
N2 - A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at a rate of 40 Hz (25-ms measurement time). The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of < 1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Noise-equivalent concentrations (1σ) (NEC) of 147.0 ppbv and 151.6 ppbv in a 25-ms measurement time are determined for D2O and HDO, respectively, with a 127-m optical path. These NECs are improved to 23.0 and 24.0 ppbv with a 1-s averaging time for D2O and HDO, respectively. NECs < 200 ppbv are also estimated for N2O, 1,1,1,2-tetrafluoroethane (F134A), CH4, acetone and SO2 for a 25-ms measurement time. The isotopic precision for measurement of the [D2O]/[HDO] concentration ratio of 33‰ and 5‰ is calculated for the current experimental conditions for measurement times of 25 ms and 1 s, respectively.
AB - A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at a rate of 40 Hz (25-ms measurement time). The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of < 1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Noise-equivalent concentrations (1σ) (NEC) of 147.0 ppbv and 151.6 ppbv in a 25-ms measurement time are determined for D2O and HDO, respectively, with a 127-m optical path. These NECs are improved to 23.0 and 24.0 ppbv with a 1-s averaging time for D2O and HDO, respectively. NECs < 200 ppbv are also estimated for N2O, 1,1,1,2-tetrafluoroethane (F134A), CH4, acetone and SO2 for a 25-ms measurement time. The isotopic precision for measurement of the [D2O]/[HDO] concentration ratio of 33‰ and 5‰ is calculated for the current experimental conditions for measurement times of 25 ms and 1 s, respectively.
KW - External cavity quantum cascade laser
KW - Infrared spectroscopy
KW - Trace-gas sensing
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U2 - 10.3390/photonics3020033
DO - 10.3390/photonics3020033
M3 - Article
AN - SCOPUS:85021796412
SN - 2304-6732
VL - 3
JO - Photonics
JF - Photonics
IS - 2
M1 - 33
ER -