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Spectral Acquisition (spectral + acquisition)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Spectral Acquisition and Calibration Techniques for the Measurement of Radiative Flux Incident upon Propellant

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003
Michael
Abstract A technique for the absolute calibration of a time-resolved spectrographic system has been developed at QinetiQ, specifically designed to be relevant to spectral acquisition from within the interior of translucent gun-propellant samples. The technique has shown itself to be particularly useful in the realm of propellant ignition as it allows for the precise determination of the moment that propellant combustion processes begin, as well as measuring the incident radiative flux leading up to ignition. Scope exists to extend its use for high-pressure measurements of the incident radiative flux during both conventional propellant burn and high-powered electrothermal-chemical (ETC) discharges. This paper sets out to describe both the technique and some of the pitfalls encountered during the development of the technique. The use of this technique in some of the experimental work performed at QinetiQ, including the results of measurements that compare the incident radiative flux with propellant ignition during both ETC discharges and conventional gunpowder burn, have been published separately; references for this experimental work are given in this paper. [source]

Cover Picture: J. Biophoton.

JOURNAL OF BIOPHOTONICS, Issue 4 2008
4/200
Pseudocolored confocal microscopy image of cryosectioned human skin visualizing the skin autofluorescence. The image was obtained by spectral acquisition and the result of an automated component extraction and linear unmixing using two components is shown as blue and green pixels. The field of view is 225 × 225 ,m. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optimum acquisition of Raman spectra in pigment analysis with IR laser diode and pulsed UV irradiation

JOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2006
Alejandro López-Gil
Abstract Fluorescence, due to the binding media, is the main problem that one encounters in the molecular analysis of artistic pigments using Raman spectroscopy. With the object of minimizing this problem, we propose the use of a semiconductor IR laser in Raman spectral acquisition and the application of local irradiation with a pulsed UV laser on the analysis zone. The Raman analysis with an IR source shows advantages compared to that with visible lasers, such as the reduction of fluorescence and its shot noise, although a price has to be paid in the form of the small intensity of the obtained spectra with the same acquisition time. Also, in this paper we demonstrate that controlled levels of pulsed UV radiation over the analyzed painting (pigment + binding media) can improve even more the Raman spectral quality obtained with the IR laser, which leads us to conclude that the local use of a pulsed UV laser, prior to Raman analysis with the IR source, can bring optimum quality results in pigment identification. The spectral quality of these experimental results for different pigments has been measured by calculating in each case the signal-to-noise ratio (SNR) of the corresponding spectra. From a quantitative point of view, in some practical cases (chromium yellow and ultramarine blue) an SNR improvement of 16 dB is achieved when pulsed UV irradiation and IR laser Raman analysis are used instead of a simple Raman analysis with a visible laser. Copyright © 2006 John Wiley & Sons, Ltd. [source]