Ethylene spectroscopy using a quasi-room-temperature quantum cascade laser

Abstract

Spectroscopic measurements on ethylene were performed using a quasi-room-temperature quantum cascade (QC) laser operated in pulsed mode in the 10.3 mm range. Using transmission spectroscopy, a broadening of the ethylene absorption spectrum was observed with increasing laser pulse duration, due to an increase of the laser linewidth. This linewidth was determined from the measured absorption spectra, showing a value of 0.04 cm − 1 for a 20 ns pulse duration and an enhancement coefficient of 6.5 × 10 − 3 cm − 1 per ns in the 20 -50 ns pulse length range. Photoacoustic (PA) detection of ethylene was also performed using the QC laser and a resonant PA cell, with a detection limit of 60 ppm.

Ozone detection by differential absorption spectroscopy at ambient pressure with a 9.6�?m pulsed quantum-cascade laser

“…This assumption allows estimating the QCL halfwidth (α L,QCL ) by subtraction of the HITRAN-based calculated transitions halfwidths (α L,σ ) from the observed halfwidths (α L,D ∼ = α L,σ + α L,QCL ). This approach has been widely used for linewidth estimation [12,15,21]. The retrieved QCL halfwidths at 0.5% dc range from 0.056 cm −1 for the P22 transition to 0.067 cm −1 for the P18 (1.7-2.0 GHz).…”

“…The advent of the quantum-cascade laser (QCL) in 1994 [8], and its rapid development during the last years [9], has opened up the possibility of using tunable, non-cryogenic, narrow linewidth sources for real-time spectroscopic monitoring of a large number of molecular species in the mid-IR, particularly in the 3-5 µm and 8-13 µm H 2 O atmospheric windows. QCL-based point measurements of several trace gases have been successfully demonstrated during the last years [10][11][12][13][14][15][16]. With few exceptions [14][15][16], these measurements have been performed at low pressure and in closed, folded optical path systems (e.g.…”

“…QCL-based point measurements of several trace gases have been successfully demonstrated during the last years [10][11][12][13][14][15][16]. With few exceptions [14][15][16], these measurements have been performed at low pressure and in closed, folded optical path systems (e.g. White or Herriott cells) for sensitivity improvement.…”

Sensitive detection of acrolein and acrylonitrile with a pulsed quantum-cascade laser

“…The inter-pulse technique, also known as rapid sweep integration, has been implemented by several groups [9][10][11][12][13][14][15] and frequency tuning ranges of up to 1 cm −1 have been reported. The laser described here provides a frequency scan of up to ∼2.3 cm −1 with this technique, similarly to what has been achieved with the intra-pulse approach.…”

Monitoring of ethylene by a pulsed quantum cascade laser

“…Trace gas detection of C 2 H 4 by use of quasi-roomtemperature pulsed QC lasers with both direct absorption spectroscopy and PAS with a 60-ppm detection limit has been reported. 13 Ethylene also was recently measured in cigarette smoke by QCL spectroscopy with a sensitivity of 150 ppb Hz Ϫ1͞2 . 14 In this paper we report on the development and performance of a 10-m QCL-based direct absorption spectrometer and its application to C 2 H 4 detection and monitoring in vehicular exhaust as well as in ambient air sampled from a high-traffic urban underground tunnel.…”