title: Absorption and wavelength modulation spectroscopy of NO2 using a tunable, external cavity continuous wave quantum cascade laser.
abstract: The absorption spectra and wavelength modulation spectroscopy (WMS) of NO(2) using a tunable, external cavity CW quantum cascade laser operating at room temperature in the region of 1625 to 1645 cm(-1) are reported. The external cavity quantum cascade laser enabled us to record continuous absorption spectra of low concentrations of NO(2) over a broad range (approximately 16 cm(-1)), demonstrating the potential for simultaneously recording the complex spectra of multiple species. This capability allows the identification of a particular species of interest with high sensitivity and selectivity. The measured spectra are in excellent agreement with the spectra from the high-resolution transmission molecular absorption database [J. Quant. Spectrosc. Radiat. Transfer 96, 139-204 (2005)]. We also conduct WMS for the first time using an external cavity quantum cascade laser, a technique that enhances the sensitivity of detection. By employing WMS, we could detect low-intensity absorption lines, which are not visible in the simple absorption spectra, and demonstrate a minimum detection limit at the 100 ppb level with a short-path absorption cell. Details of the tunable, external cavity quantum cascade laser system and its performance are discussed.
authors.affiliation: Department of Physics, Adelphi University, Garden City, New York 11530, USA. karpf@adelphi.edu
authors.forename: Andreas
authors.initials: A
authors.lastname: Karpf
authors.forename: Gottipaty N
authors.initials: GN
authors.lastname: Rao
mesh_terms: D000042:Absorption; D055592:Biophysical Phenomena; D004867:Equipment Design; D007834:Lasers; D054023:Lasers, Semiconductor; D009585:Nitrogen Dioxide / Q000737:chemistry*; D055095:Optics and Photonics; D015203:Reproducibility of Results; D013053:Spectrophotometry / Q000295:instrumentation* / Q000379:methods*; D013696:Temperature
chemical_list: D009585:Nitrogen Dioxide