title: Ppb-level detection of nitric oxide using an external cavity quantum cascade laser based QEPAS sensor.
abstract: Geometrical parameters of micro-resonator for a quartz enhanced photoacoustic spectroscopy sensor are optimized to perform sensitive and background-free spectroscopic measurements using mid-IR quantum cascade laser (QCL) excitation sources. Such an optimized configuration is applied to nitric oxide (NO) detection at 1900.08 cm(-1) (5.26 µm) with a widely tunable, mode-hop-free external cavity QCL. For a selected NO absorption line that is free from H(2)O and CO(2) interference, a NO detection sensitivity of 4.9 parts per billion by volume is achieved with a 1-s averaging time and 66 mW optical excitation power. This NO detection limit is determined at an optimal gas pressure of 210 Torr and 2.5% of water vapor concentration. Water is added to the analyzed mixture in order to improve the NO vibrational-translational relaxation process.
authors: Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA. lei.dong@rice.edu
authors: Lei
authors: L
authors: Dong
authors: Vincenzo
authors: V
authors: Spagnolo
authors: Rafał
authors: R
authors: Lewicki
authors: Frank K
authors: FK
authors: Tittel
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D009569:Nitric Oxide / Q000032:analysis*; D014159:Transducers
chemical_list: D009569:Nitric Oxide