Eur. Phys. J. D 19, 327-331 (2002)
https://doi.org/10.1140/epjd/e20020091

Sensitive detection of methane and nitrous oxide isotopomers using a continuous wave quantum cascade laser

¹ European Laboratory for Non-Linear Spectroscopy and Istituto Nazionale per la Fisica della Materia, University of Firenze, largo E. Fermi 2, 50125 Firenze, Italy
² Istituto Nazionale di Ottica Applicata, largo E. Fermi 6, 50125 Firenze, Italy
³ Bell Laboratories, Lucent Technologies, 600 Mountain avenue, Murray Hill, NJ 07974, USA

Corresponding author: ^a gagliardi@na.infn.it

Received: 14 March 2002
Published online: 15 June 2002

Abstract

A continuous wave quantum cascade laser (QCL), operating near 8.1 μm, was used for wavelength modulation spectroscopy of methane (CH₄) and nitrous oxide (N₂O) stable isotopes. Several rotational transitions of ¹⁴N₂ ¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N₂ ¹⁸O, ¹⁴N₂ ¹⁷O, ¹³CH₄ and ¹²CH₄ fundamental bands were detected. The noise-equivalent absorbance was measured to be less than 10^-5 in a 1-Hz bandwidth. A characterization of the laser source was also performed. The use of a QCL spectrometer for high-precision isotope ratio measurements is discussed.