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Spectroscopic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
In the infrared region, the common sources are electrically heated elements made of ceramic or alloys. The Nernst glower is composed of rare earth oxides, operates up to about 1800 K, and has a negative coefficient of electrical resistance. This means that the resistance becomes lower as the source is heated, and it may require preheating before a current can be passed at all. The globar is a silicon carbide rod, which operates at a lower temperature, about 1600 K, and gives more radiation in the region below 1500 cm−1 than does the Nernst glower. A characteristic of all the IR sources is their generally low output of radiation. This means that IR spectroscopy is generally energy limited, and requires sensitive detection.
Light Sources
Published in Roshan L. Aggarwal, Kambiz Alavi, Introduction to Optical Components, 2018
Roshan L. Aggarwal, Kambiz Alavi
A tungsten filament is used for VIS and IR spectroscopy. A Nernst lamp uses a ceramic rod that is heated to incandescence. The ceramic rod does not need to be enclosed within a vacuum or noble gas environment, because the rod would not further oxidize when exposed to air. Walther Nernst, a German physicist and chemist, developed the Nernst lamp in 1897 at Goettingen University. Nernst lamps are no longer used for IR spectroscopy. At 1250°K–1900°K, Globar (a silicon carbide rod) emits radiation in the 4–15 μm region and is used as a thermal light source for IR spectroscopy. The spectral behavior of a Globar is approximately that of a blackbody.
Vibrational Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Peter Fredericks, Llewellyn Rintoul, John Coates
A robust source designed for operation at higher temperatures and for high output is the Globar—an electrically heated rod made from silicon carbide. For some implementations, the high power output associated with this source results in an excessive amount of heat being dissipated within the instrument. In such circumstances, supplemental water-cooling is applied, to remove excess heat, and to help reduce thermal/oxidative degradation of the electrical contacts.
Line intensity parameters, He-broadening and line shift coefficients in the 2v 2 0 and 3v 2 1 − v 2 1 bands of OCS
Published in Molecular Physics, 2022
N. Dridi, C. Jellali, F. Hmida, L. Hui, F. Kwabia Tchana, X. Landsheere, K. Hammami, M. Rotger, H. Aroui
The instrument was equipped with a KBr/Ge beamsplitter, a silicon carbide globar source and a liquid nitrogen cooled Mercury Cadmium Telluride (MCT) detector. The aperture diameter (1.3 mm) of the spectrometer was set to maximise the intensity of IR radiation arriving on the MCT detector without saturation or loss of spectral resolution. Spectra were recorded with a 40 kHz scanner frequency and a maximum optical path difference dMOPD of 225 cm. According to the Bruker definition (Resolution = 0.9/dMOPD), this corresponds to a resolution of 0.004 cm−1. The interferometer was coupled to a White-type multipass absorption cell, made of pyrex glass and equipped with CsBr windows with a path length of 1.649(10) m. The OCS sample with a stated purity of 97.5% was purchased from Sigma Aldrich. The high purity helium (99.99%) sample was provided by Air Liquide. No further sample purifications were done. The spectra were recorded at a stabilised room temperature of 295 ± 1 K and were ratioed against a single channel background spectrum of the empty cell recorded at a resolution of 0.2 cm−1 in order to ensure the best possible signal-to-noise in the ratioed spectra. Every interferogram was transformed into a spectrum using the procedure included in the Bruker software OPUS package [21,22] with the Mertz phase error correction method, a 1 cm−1 phase resolution, a zero-filling factor of 2 and no apodization (boxcar option) was applied. The peak-to-peak signal-to-noise ratio in the ratioed spectra is around 800 at the P- and R-branch centres.
The analysis of the Coriolis interactions in the v10 = 1, v7 = 1 and v4 = 1 triad rovibrational states of 13C2D4 by high-resolution FTIR spectroscopy
Published in Molecular Physics, 2020
The 13C2D4 gas sample used in the experiment was procured from Cambridge Isotope Laboratories in Massachusetts, USA and has a chemical purity of better than 98%. Four spectra of samples at gas pressures of 0.20, 0.61, 1.02 and 5.53 mbar were recorded in the 515 cm−1–825 cm−1 wavenumber region at an unapodised resolution of 0.0019 cm−1 using the Bruker IFS 125 HR spectrometer located in National Institute of Education, Nanyang Technological University of Singapore. The spectrometer uses a globar infrared source, a high-sensitivity MCT detector cooled with liquid-nitrogen, and a KBr beamsplitter. Spectra collection was typically carried out at an ambient temperature of 296 K. A total absorption path length of 8.0 m was used by adjusting for 40 passes in the multiple-pass gas cell with 0.20 m base length. The gas pressures as measured by the capacitance pressure gauge, numbers of co-added scans and the total scanning times of the respective spectra are listed in Table 1. The interferograms were processed with a 4-point apodization function and a post-zero fill factor of 8. The full-width at half maximum (FWHM) of the absorption lines were measured to have an average value of 0.003 cm−1 due to a combination of pressure and Doppler broadenings.
Treatment of textile wastewater using monolayered ultrafiltation ceramic membrane fabricated from natural kaolin clay
Published in Environmental Technology, 2021
Saida Bousbih, Emna Errais, Fadila Darragi, Joelle Duplay, Malika Trabelsi-Ayadi, Michael Olawale Daramola, Raja Ben Amar
The clay powder was characterized using different techniques. Phase identification was performed using XRD diffractometer (Bruker D5000). The chemical composition of the clay was determined by X-ray fluorescence. A thermogravimetric analysis instrument (TGA 2950 model, SDT Q600) was used to study the thermal degradation behaviour of the sample under argon and at a heating rate of 5°C/min from room temperature to 1100°C. Fourier-transform infrared (FTIR) analysis was performed with NICOLET IS10 Thermo-Scientific spectrometer equipped with a Globar source and a DTGS detector (wavenumber ranged from 400 cm−1– to 4000 cm−1).