We report on the development and performance of a gas sensor based on a quantum cascade laser operating at a wavelength of approximately 10 microns to measure ethylene (C2H4) concentrations by use of a rotational component of the fundamental nu 7 band. The laser is thermoelectrically cooled and operates in a pulsed mode. The influence of pulse-to-pulse… (More)
Simultaneous exhaled carbonyl sulfide (OCS) and carbon dioxide concentration measurements in human breath are demonstrated with a compact pulsed quantum-cascade laser-based gas sensor. We achieved a noise-equivalent sensitivity (1sigma) of 1.2 parts per billion by measuring a well-isolated OCS P(11) absorption line in the v3 band at 2057.6 cm(-1) using an… (More)
A near-infrared diode laser with sample-grating distributed Bragg reflectors was used as a widely tunable spectroscopic source for multispecies chemical sensing. Quartz-enhanced photoacoustic spectroscopy was utilized to obtain high absorption sensitivity in a compact gas cell. CO2, H2O C2H2, and NH3 were monitored. A noise equivalent sensitivity of 8 x… (More)
A spectroscopic detection of molecular dispersion based on frequency-chirped laser is presented. Unlike non-linear direct absorption methods yielding line saturation, this method provides linear signal response and accuracy over a wide range of sample concentrations.
The report of an IUPAC Task Group, formed in 2011 on " Intensities and line shapes in high-resolution spectra of water isotopologues from experiment and theory " (Project No. 2011-022-2-100), on line profiles of isolated high-resolution rotational-vibrational transitions perturbed by neutral gas-phase molecules is presented. The well-documented inadequacies… (More)
Expired breath δ(13)CO2 measured in real time serves as a useful biomarker of altered macronutrient metabolism in response to changes in energy balance. Altered breath δ(13)CO2 is believed to be a result of changes in macronutrient oxidation and the kinetic isotope effect where enzymatic processes discriminate against metabolites naturally enriched with… (More)
An active spectrometer has been developed based on diffuse backscattering by solid targets combined with coherent detection and mid-infrared quantum cascade lasers. High selectivity and sensitivity have been shown at standoff distances of 40 m.
A molecular detection method based on laser dispersion spectroscopy has been implemented to detect methane concentrations with an open-path configuration and using transitions from the ν<sub>4</sub> band. Preliminary results on transient seeps are presented.
A method for obtaining high-quality 2D-IR spectra of gas-phase samples is presented. Time-resolved IR absorption spectroscopy techniques, such as 2D-IR spectroscopy, often require that beams are focused into the sample. This limits the exploitable overlapped path length through samples to a few millimeters. To circumvent this limitation, 2D-IR experiments… (More)