Fourier Transform Infrared Spectroscopy for the Measurement of Spectral Line Profiles

Aroui, H.; Orphal, J.; Tchana, F. Kwabia

doi:10.5772/36120

Cited by 7 publications

(5 citation statements)

References 71 publications

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“…To minimize the root-mean-square deviation between measured and calculated extinction spectrum, we used the downhill simplex algorithm as the optimization technique in the iterative adjustment of the k(ν) spectrum (Press et al, 1992). The measured spectrum is provided in a digital resolution of about 0.24 cm −1 , resulting from an approximately doubled size of the original interferogram due to zerofilling with a factor of 2 (Aroui et al, 2012). Overall, this amounts to 21 572 wavenumber grid points for the k(ν) spectrum in the wavenumber range between 800 and 6000 cm −1 .…”

Section: Application Of the New Refractive Index Data Setmentioning

confidence: 99%

High-resolution optical constants of crystalline ammonium nitrate for infrared remote sensing of the Asian Tropopause Aerosol Layer

et al. 2021

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Abstract. Infrared spectroscopic observations have shown that crystalline ammonium nitrate (AN) particles are an abundant constituent of the upper tropospheric aerosol layer which is formed during the Asian summer monsoon period, the so-called Asian Tropopause Aerosol Layer (ATAL). At upper tropospheric temperatures, the thermodynamically stable phase of AN is different from that at 298 K, meaning that presently available room-temperature optical constants of AN, that is, the real and imaginary parts of the complex refractive index, cannot be applied for the quantitative analysis of these infrared measurements. In this work, we have retrieved the first low-temperature data set of optical constants for crystalline AN in the 800–6000 cm−1 wavenumber range with a spectral resolution of 0.5 cm−1. The optical constants were iteratively derived from an infrared extinction spectrum of 1 µm sized AN particles suspended in a cloud chamber at 223 K. The uncertainties of the new data set were carefully assessed in a comprehensive sensitivity analysis. We show that our data accurately fit aircraft-borne infrared measurements of ammonium nitrate particles in the ATAL.

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Section: Application Of the New Refractive Index Data Setmentioning

confidence: 99%

High-resolution optical constants of crystalline ammonium nitrate for infrared remote sensing of the Asian Tropopause Aerosol Layer

et al. 2021

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“…4, trace b), which, similar to the spectrum of the annealed particles mentioned in the Introduction, clearly exhibits the spectral characteristics of -NAD reported in . The spectrum was interpolated to the wavenumber grid of our measurement, which was provided at a digital resolution of about 2 cm -1 , resulting from an approximate doubling of the size of the original interferogram due to zero-filling by a factor of two (Aroui et al, 2012). For thin film spectra, the absorbance is directly proportional to 𝑘( ̃) •  ̃.…”

Section: Retrieval Scheme For Deriving the Optical Constants Of -Nadmentioning

confidence: 99%

Particle shapes and infrared extinction spectra of nitric acid dihydrate crystals: Optical constants of the β-NAD modification

Wagner

James

Frankland

et al. 2023

Preprint

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Abstract. Satellite- and aircraft-based mid-infrared measurements of polar stratospheric clouds (PSCs) have provided spectroscopic evidence for the presence of β-NAT (nitric acid trihydrate) particles. Metastable nitric acid hydrate phases such as α-NAT and α-NAD (nitric acid dihydrate) have been frequently observed in laboratory experiments, but not yet detected as a constituent of PSCs in atmospheric measurements. As for the β-NAD modification, its formation was first observed in X-ray diffraction measurements when the low-temperature α-NAD phase was warmed to a temperature above 210 K. Its infrared spectrum has been reported, but so far no optical constants have been derived that could be used as input for infrared retrievals of PSC composition. In this work, we show that β-NAD particles were efficiently formed in isothermal, heterogeneous crystallisation experiments at 190 K from supercooled HNO3/H2O solution droplets containing an embedded mineral dust or meteoric smoke particle analogue. An inversion algorithm based on a T-matrix optical model was used to derive for the first time the mid-infrared complex refractive indices of the β-NAD modification from the measured extinction spectrum of the particles. In contrast to the heterogeneous crystallisation experiments, the α-NAD phase was formed when the HNO3/H2O solution droplets did not contain a solid nucleus and crystallised homogeneously. Using a light scattering detector that recorded two-dimensional scattering patterns of the crystallised NAD particles, we were able to determine predominant shapes of the α- and β-NAD crystals. We found that α-NAD grew into elongated, needle-shaped crystals, while β-NAD particles were compact in shape. This agrees with previously reported images of α- and β-NAD particles grown on the cryo-stage of an Environmental Scanning Electron Microscope.

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“…FTIR spectroscopy is used to quickly and definitively detect chemicals. It can be used in all stages of the product lifecycle, including design, manufacturing, and failure analysis [47,48].…”

Section: Fourier Transform Infrared Spectroscopy (Ftir)mentioning

confidence: 99%

Fabrication of ZnO/CNTs for Application in CO2 Sensor at Room Temperature

et al. 2021

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Thin films of ZnO and ZnO/carbon nanotubes (CNTs) are prepared and used as CO2 gas sensors. The spray pyrolysis method was used to prepare both ZnO and ZnO/CNTs films, with CNTs first prepared using the chemical vapor deposition method (CVD). The chemical structure and optical analyses for all the prepared nanomaterials were performed using X-ray diffraction (XRD), Fourier transformer infrared spectroscopy (FTIR), and UV/Vis spectrophotometer devices, respectively. According to the XRD analysis, the crystal sizes of ZnO and ZnO/CNTs were approximately 50.4 and 65.2 nm, respectively. CNTs have average inner and outer diameters of about 3 and 13 nm respectively, according to the transmitted electron microscope (TEM), and a wall thickness of about 5 nm. The detection of CO2 is accomplished by passing varying rates of the gas from 30 to 150 sccm over the prepared thin-film electrodes. At 150 sccm, the sensitivities of ZnO and ZnO/CNTs sensors are 6.8% and 22.4%, respectively. The ZnO/CNTs sensor has a very stable sensitivity to CO2 gas for 21 days. Moreover, this sensor has a high selectivity to CO2 in comparison with other gases, in which the ZnO/CNTs sensor has a higher sensitivity to CO2 compared to H2 and C2H2.

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Fourier Transform Infrared Spectroscopy for the Measurement of Spectral Line Profiles

Cited by 7 publications

References 71 publications

High-resolution optical constants of crystalline ammonium nitrate for infrared remote sensing of the Asian Tropopause Aerosol Layer

High-resolution optical constants of crystalline ammonium nitrate for infrared remote sensing of the Asian Tropopause Aerosol Layer

Particle shapes and infrared extinction spectra of nitric acid dihydrate crystals: Optical constants of the β-NAD modification

Fabrication of ZnO/CNTs for Application in CO2 Sensor at Room Temperature

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