Topic
Fourier transform spectroscopy
About: Fourier transform spectroscopy is a research topic. Over the lifetime, 5418 publications have been published within this topic receiving 134133 citations.
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Abstract: Spectroscopic ellipsometry is a means to investigate optical and dielectric material responses. Conventional spectroscopic ellipsometry has trade-offs between spectral accuracy, resolution, and measurement time. Polarization modulation has afforded poor performance due to its sensitivity to mechanical vibrational noise, thermal instability, and polarization wavelength dependency. We equip a spectroscopic ellipsometer with dual-optical-comb spectroscopy, viz. dual-optical-comb spectroscopic ellipsometry (DCSE). The DCSE directly and simultaneously obtains amplitude and phase information with ultra-high spectral precision that is beyond the conventional limit. This precision is due to the automatic time-sweeping acquisition of the interferogram using Fourier transform spectroscopy and optical combs with well-defined frequency. Ellipsometric evaluation without polarization modulation also enhances the stability and robustness of the system. In this study, we evaluate the DCSE of birefringent materials and thin films, which showed improved spectral accuracy and a resolution of up to 1.2x10-5 nm across a 5-10 THz spectral bandwidth without any mechanical movement.
36 citations
TL;DR: In this article, a linear motion sample transport (TRANSCELL) was attached to the FTS, which increased the area scanned from 2 mm in diameter (stationary cell or STATCELL), to 2 X 50 mm.
Abstract: The objective of this research was to determine whether diffuse reflectance calibrations using a Fourier transform spectrometer (FTS) could be improved by increasing the scanned sample area. A linear motion sample transport (TRANSCELL) was attached to the FTS, which increased the area scanned from 2 mm in diameter (stationary cell or STATCELL) to 2 X 50 mm. Sodium chlorite-treated forages and by-products (N = 174) were scanned in the near-infrared (NIR) and mid-infrared (MIR) with the use of the TRANSCELL and STATCELL. Samples were analyzed for fiber, digestibility, lignin, protein, and lignin nitrobenzene oxidation products (NOPs). Overall, the best results for fiber, lignin, and digestibility were achieved by using MIR spectra and the TRANSCELL. Results in the NIR (FTS) with the use of the TRANSCELL were also improved over those obtained with the STATCELL. While the TRANSCELL was an improvement over the STATCELL for Fourier NIR analysis of NOPs, in the MIR, results for NOPs were about equal for the TRANSCELL and STATCELL. In conclusion, the use of a TRANSCELL can improve calibrations from Fourier transform spectrometers, although the degree of improvement depends on the spectral region and specific calibration under study.
36 citations
TL;DR: A novel humidity sensor made up of nano-crystalline zinc oxide (ZnO) film, coated onto the U-shaped typical glass substrate as a wave guide, conjugated with an optical fiber and He-Ne un-polarized laser source.
36 citations
TL;DR: In this article, a large number of spin-rovibronic levels of the upper electronic state of NH2 have been excited with a single mode rhodamine 6G dye laser.
Abstract: A large number of spin-rovibronic levels of the upper electronic state of NH2 have been excited with a single mode rhodamine 6G dye laser. Fluorescence spectra were obtained over a wide spectral range (12 000-3700 cm-1) using a Fourier transform spectrometer. Levels of the bending vibration were observed from ν″2 = 4 up to 10, showing the reordering of the K-structure at the barrier to linearity; their observed energies are in good agreement with the predictions of Jungen, Hallin and Merer [16, 17], Duxbury and Dixon [19] and Peric, Peyerimhoff and Buenker [20]. Numerous vibrational levels involving nv 1 and 2v 3 were also detected and approximate anharmonic parameters have been deduced. Local perturbations are observed and discussed; the interpretations proposed by Jungen et al. [18] for some of these in the A 2 A 1 state are experimentally confirmed.
36 citations
TL;DR: In this article, Fourier transform spectrometers were used for measuring 294 Ba I lines and 52 Ba II lines with uncertainties in the range ±0.001 cm-1 to ± 0.01 cm- 1.
Abstract: Barium spectra emitted from hollow cathode discharges and recorded with Fourier transform spectrometers in the region 1700–31 000 A have been used for measuring 294 Ba I lines and 52 Ba II lines with uncertainties in the range ±0.001 cm-1 to ±0.01 cm-1. Energy level values have been derived from the measurements. The energy levels have been used for an improved determination of the Ba II ionization limit, giving the value 80686.30 ± 0.10 cm-1.
36 citations