Detection and quantification of multiple molecular species in mainstream cigarette smoke by continuous-wave terahertz spectroscopy

Abstract

Continuous-wave terahertz spectroscopy by photomixing is applied to the analysis of mainstream cigarette smoke. Using the wide tunability of the source, spectral signatures of hydrogen cyanide (HCN), carbon monoxide (CO), formaldehyde (H2CO), and water (H2O) have been observed from 500 to 2400 GHz. The fine spectral purity allows direct concentration measurement from the pure rotational transitions of HCN and CO. The quantification of the measurement was validated by the means of a calibration gas containing CO. The potential of this technique for trace gas detection is demonstrated with an estimated detection limit of HCN equal to 9 parts in 10(6).

Terahertz gas sensor based on absorption-induced transparency

“…, C = 96.79 GHz, and X = 1239.89 GHz, which enable us to reproduce the experimental absorption spectrum obtained by Bigourd et al [23]. The experimental sample consisted in a d = 1240 mm length cell containing HCN, at concentration of %210 ppm and Continuos-Wave spectroscopy was used to conduct the measurements (see Figure 1; for additional details on the experiments, see [23,24]).…”

“…Namely, the target absorption line of the HCN compound spectrally located at frequency 1239.89 GHz with a full-width at half maximum of 126 MHz [23]. The contribution to the dielectric constant of HCN from this absorption line is well represented by a Lorentz function in the frequency domain, which provides suitable optical response in the spectral window of interest for this gas, e HCN (m) = e inf À DeX…”

“…The experimental sample consisted in a d = 1240 mm length cell containing HCN, at concentration of %210 ppm and Continuos-Wave spectroscopy was used to conduct the measurements (see Figure 1; for additional details on the experiments, see [23,24]). Transmission was then calculated as:…”

Terahertz spectroscopy: The renaissance of far infrared spectroscopy

“…Continuous-wave terahertz spectra obtained by photo-mixing different laser beams were used to analyse mainstream cigarette smoke [29]. Characteristic terahertz spectral signatures were observed in the 0.5-2.4 THz range for hydrogen cyanide (HCN), carbon monoxide (CO), formaldehyde (H 2 CO), and water (H 2 O) allowing investigators to identify and quantify the individual gases, achieving direct concentration measurements from the pure rotational transitions.…”

Active imaging with incoherent sub-terahertz radiation in smoky environments

“…Terahertz (THz) waves have a much longer wavelength than the diameter of smoke particles and can penetrate smoke [2][3][4][5]. If they can be used to observations, a clear view can be ensured even in severe smoky environments with poor visibility.…”