Deep Ultraviolet Resonance Raman Spectroscopy of Explosives

Water plays a critical role in dental tissues including enamel and dentin. The characterization of water structure was primarily conducted by nuclear magnetic resonance. Raman spectroscopy is a powerful analytic technology with capability for structure analysis in materials. However, acquiring high wavenumber Raman signals from dental tissues was challenging due to either the fluorescence interference under laser illumination or reduced sensitivity of charge‐coupled device based detectors. In this study, we demonstrate a pilot research on high wavenumber Raman analysis in dental tissues using a customized Raman spectrometer based on an InGaAs detector. A signal located at 3,570 cm−1 is found dominating the O─H region Raman spectra of enamel but is barely detectable from dentin. The profiles of the high wavenumber region Raman spectra change with the locations in enamel, as well as the polarization of the excitation laser beam. The results suggest that the size or crystallinity differences of hydroxyapatite crystals are the main cause of the spectral variation from dentin to enamel and could be partially responsible for the variation among different locations in enamel.

Section: Resultsmentioning

confidence: 87%

A pilot study on high wavenumber Raman analysis of human dental tissues

Livingston

Sobiesk

et al. 2019

“…In Table 1, we present the dependence of estimated local temperature T on excitation He-Ne laser power according to the Stokes/anti-Stokes ratio. The estimation of local temperature was accomplished using Equation (1) [16]…”

Section: Resultsmentioning

confidence: 99%

“…Raman spectroscopy is known as a powerful optical tool to estimate local temperature by measuring the Stokes to anti-Stokes ratio. [13][14][15][16] It was demonstrated that intense laser radiation focused on the surface of such bulk semiconductors as Si and Ge can heat and melt them. [17] Moreover, heating effects often take place in nanostructures and may be reversible [18][19][20][21] or may be irreversible.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Stokes to anti‐Stokes ratio for germanium nanowires obtained by electrochemical deposition

Pavlikov

Форш

Кашкаров

et al. 2020

Germanium nanowires fabricated by the electrochemical liquid–liquid–solid deposition from water solutions on titanium coated silicon substrate were studied by Raman spectroscopy in order to estimate the heating effect of exciting radiation. The Stokes to anti‐Stokes ratio was determined for crystalline Ge wafer and for nanowires with different mean diameters at two different excitation wavelengths. It was demonstrated that local heating by exciting laser radiation can lead to an increase in temperature sufficiently high for crystallization of initially amorphous Ge nanowires. The results presented may be of great use for fabricating devices, such as metal ion batteries or thermoelectric elements, based on Ge nanowire.

“…The fourth band at 790 cm −1 is assigned to the mode T 1 . [24] At the three different laser powers, the signals are still high enough to be identified. We thus observed that the SHRS exhibited excellent sensitivity.…”

Section: Calibrationmentioning

confidence: 95%

Raman measurements using a field‐widened spatial heterodyne Raman spectrometer

Qiu

et al. 2019

Spatial heterodyne Raman spectroscopy has become a useful spectroscopic detection technique that is particularly suitable for Raman measurements. This method uses the Fourier transform of the interferogram imaged on the detector by stationary diffraction gratings. Spatial heterodyne Raman spectroscopy has the same characteristic of conventional Fourier‐transform spectroscopy, which is that the field of view is limited. We propose a two‐dimensional spatial heterodyne Raman spectrometer (SHRS) that uses a field widening prism to effectively increase the throughput or sensitivity without sacrificing the spectral resolution for Raman measurements while broadening the bandpass. The signal‐to‐noise ratio is measured under different integrations or laser powers and shows that the system exhibits good stability and fair repeatability. Raman spectra obtained from the field‐widened SHRS and a commercialized Raman instrument are compared, and the field‐widened SHRS and the SHRS using the same instrumental parameters without field widening are also compared. A higher signal‐to‐noise ratio can be achieved using the field‐widened SHRS. In our measurements, the field‐widened SHRS can be operated under the slightly more complex conditions required for wide‐field measurements with short integration times and low laser power. Raman spectra of a pure inorganic target or a target contained in glass and a plastic bottle are observed. A sulfate is investigated in two states: solid salt and aqueous solution. Several mixture liquids, mixture solids, minerals, and anti‐Stokes Raman shifts are also investigated. The results show that the field‐widened SHRS exhibits a good performance to successfully perform wide‐field Raman measurements.